Basic Electronics/Electrical Projects & Kits

Get our latest collection of basic electronics projects here -- all tested and reviewed for use in mini projects and main projects or even just as hobbyist projects!
School/College Quiz Buzzer Save Rs. 200.00
Rs. 750.00
Rs. 550.00

School/College Quiz Buzzer

School/College Quiz Buzzer

by KNS Pvt Ltd
Save Rs. 200.00
Rs. 750.00
Rs. 550.00

Summary

Manual buzzers used for quiz competitions in schools and colleges create a lot of confusion in identifying the first respondent. Although there are circuits using PCs and discrete ICs, they are either too expensive or limited to only a few number of players. The School/College Buzzer is a circuit that can be used for up to eight players.It uses the IC 74LS373 (which is an octal latch) and a few passive components to implement the quiz buzzer mechanism.

Learning

Things Which you will learn:
*Application of the octal latch IC 74LS3737.
*Use of SCRs in logic circuits.
*Application of transistors as switches.

Product Description

Quiz competition is an integral part of our learning and as the world advances towards technological advancement, there should be some changes in the way we conduct a quiz. So with this kit, you can build yourself a digital quiz buzzer supporting upto eight players and enjoy playing quiz without any confusion.

 

Working

At the heart of the School/College, Quiz Buzzer is the IC 74LS373 which transfers the logic state at data input pins (D0 through D7) to the corresponding outputs (Q0 through Q7). Data pins D0 through D7 are normally pulled low by resistors. One terminal of eight push-to-on switches (S1 through S8) is connected to +5V, while the other terminal is connected to the respective data input pins. The switches are to be extended to the players through cord wire.

The torch bulbs (BL1 through BL8) can be housed in boxes with the front side of the boxes covered with a white paper having the name or number of the contestant written over it for easy identification. When the power is switched on using switch S9 (provided terminals ‘A’ and ‘B’ of both the power supply and quiz buzzer sections are interconnected), the circuit is ready to be used.

Now all the switches (S1 through S8) are open and Q0 through Q7 outputs of IC 74LS373 (IC2) are low. As a result, the gates of silicon-controlled rectifiers (SCR1 through SCR8) are also low. As soon as a contestant momentarily presses his respective switch, the corresponding output data pin goes high.

This triggers the corresponding SCR and the respective bulb glows. At the same time, the piezoelectric buzzer (PZ1) sounds as transistor BC548 (T1) conducts. Simultaneously, the base of transistor BC548 (T2) becomes high to make it conduct. Latch-enable (LE) pin 11 of IC2 is tied to ground to latch all the Q0 through Q7 outputs. This restricts further change in the output state due to any change in the state of switches S1 through S8 by any other contestant.

Only one of the eight torch bulbs glows until the circuit is reset by on/off switch S9.

 

Download PDF for this project.

FM Booster Save Rs. 25.00
Rs. 125.00
Rs. 100.00

FM Booster

FM Booster

by KNS Pvt Ltd
Save Rs. 25.00
Rs. 125.00
Rs. 100.00

Summary

FM booster is a low-cost circuit that can be fed between an FM receiver and antenna to listen to distant commercial FM stations clearly.The main components of the circuit comprise of CS2570 transistor, trimmers and inductor coils.

Learning

Things which you can learn:
*Application of C2570 transistor.
*Working of trimmers.
*Maximum Power Transmission
*RF pre amplifier setup.

Product Description

The FM booster can be used to listen to programs from distant FM stations clearly It basically extends the range by which distant channels can be received.

Working

The circuit comprises a common-emitter tuned RF preamplifier wired around VHF/UHF transistor 2SC2570.

The input/output trimmers (VC1/VC2) for a set for maximum gain. An input coil L1 consisting of four turns of 20SWG enameled copper wire (slightly space wound) over 5mm diameter former, is tapped at the first turn from the ground lead side. Coil L2 is similar to L1 but has only three turns.

Click To View Circuit Diagram

Click here to Download PDF

Quality FM Transmitter Save Rs. 100.00
Rs. 300.00
Rs. 200.00

Quality FM Transmitter

Quality FM Transmitter

by KNS Pvt Ltd
Save Rs. 100.00
Rs. 300.00
Rs. 200.00

Summary

The digital like sound quality that FM offers is the reason that many people prefer to have their own transmitting station in FM band. The Quality FM Transmitter can transmit a chosen music piece in the FM band. To receive its signals, any conventional FM radio receiver can be used. It provides an easy way to transmit less distorted, low noise music with in a range of about 200 meters.

Just build yourself a simple FM transmitter, plug in the input via mobile or any other source and off you go with your own radio channel.Sounds exciting right !!

Learning

Things which you can learn:
*Application of transistor as amplifier.
*Working of variable resistor and trimmers.
*Concept and implementation of VHF using LC tuning Circuit
*Concept and implementation of Frequency modulation and antenna matching network
*Gain and maximum power transmission

Product Description

The Quality FM Transmitter provides good signal strength up to a distance of 500meters with a power output of about 200 mW. It works off a 9V battery. The input to the transmitter can be given by various sources like mobile phones, mp3 players etc.

Working

The audio-frequency modulation stage is built around transistor BF494 (T1), which is wired as a VHF oscillator and modulates the audio signal present at the base. Using preset VR1, one can adjust the audio signal level. The VHF frequency is decided by coil L1 and variable capacitor VC1. By reducing the value of VR2, a greater power output can be achieved. The next stage is built around transistor BC548 (T2), which serves as a Class-A power amplifier. This stage is inductively coupled to the audio-frequency modulation stage. The antenna matching network consists of variable capacitor VC2 and capacitor C9. By adjusting VC2, maximum power transmission and signal strength can be attained at the receiver end.

Click To View Circuit Diagram

Click here to Download PDF

Simple Automatic Water Level Controller Save Rs. 45.00

Simple Automatic Water Level Controller

by KNS Pvt Ltd
Save Rs. 45.00
Rs. 225.00
Rs. 180.00

Summary

This is a simple Automatic water controller Kit which the users can assemble in minutes and starting experimenting with it. The circuit is built around a TIMER555 and a inverting buffer CD4049. Circuit works on a 12V DC supply. Three sensors are installed with the kit to indicate lower level, higher level and VCC. At bottom of the tank VCC is placed,lower level L is placed above the VCC and higher level H is placed at the top.

Get the kit now and build yourself a reliable water controller and get amazed by how this tiny little device takes care of water level in the tank!!

Learning

Things Which you can learn:

*Application of NE555 timer.
*Application of CD4069 as inverter.
*Application and connection of relay switches to control the on/off of appliances.

Product Description

Water-level controllers are common nowadays and have become essential device in conserving water which otherwise would get wasted as the tank gets full up to its brim. The one described here is built around timer NE555 and inverter buffer CMOS IC CD4049. It uses readily-available, low-cost components, and is easy to build and install on the over-head tank (OHT) to prevent wastage of water.

Working


The circuit works off a 12V battery or 230V AC mains using a 12V adaptor. Since Vcc terminal is at the bottom of the tank, when the water level falls below sensor L, timer IC2 is triggered at pin 2 via inverters N1 and N2 and its output goes high. As a result, the output of timer IC2 goes high. Relay RL1 energises and the motor starts filling water in the tank. The motor remains ‘on’ even when the water level crosses sensor L.

As water in the tank rises to touch sensor H, timer IC2 is retriggered at pin 6 via inverters N3 and N4 and as a result, its outputgoes low. The relay de-energises and
the motor stops filling water in the tank. The motor remains ‘off’ even when the water level falls below sensor H. As water is consumed and its level falls below sensor L, the motor restarts.Thereafter, the cycle repeats.

Brand: Kits'n'spares, Marketed by: Kits'n'spares

 

Click here to Download PDF

 

Design Your Own LI-FI Dongle And Speaker Save Rs. 60.00

Design Your Own LI-FI Dongle And Speaker

by KNS Pvt Ltd
Save Rs. 60.00
Rs. 400.00
Rs. 340.00

Summary

Light Fidelity (Li-Fi) is a new paradigm in wireless communication. In this project, you can learn to design a Li-Fi dongle (transmitter) and speaker (receiver) for audio and music applications. The proposed system is a replacement for wired speakers that play audio signals received through the light.

Product Description

How It works?

1. The LED light in a room is used not just to light up the room but also to play music, thus giving benefits of both the worlds. Also, LED bulbs use 85 per cent less energy than
incandescent bulbs and last up to 20 times longer, whereas the majority of Bluetooth modules are battery powered and generally last a year or two only before they need replacement. Hence the proposed system is energyefficient over Bluetooth version.

2. You can receive Li-Fi data as long as you are in the range of the light being emitted by the LED light source. Hence, the range depends on the strength of the light being emitted.

3. Connectivity needs to be established between the Bluetooth transmitter and the receiver, whereas with Li-Fi any user can receive data and play music on his speaker by simply keeping the receiver in the range of LED light source.

4. The proposed system can be used with any audio system by just connecting the Li-Fi dongle to its audio output jack, with no pairing and connectivity requests. This overcomes the problem of connecting a Bluetooth speaker to audio systems that do not have USB port and Bluetooth support, which is otherwise a tougher task.

5. The proposed Li-Fi dongle and speaker costs lower than a Bluetooth dongle and speaker. It uses a Li-Fi dongle to transmit audio signals from a source such as mobile phone, and a Li-Fi speaker with solar cells at the receiver end to receive audio signals without wires. The proposed Li-Fi dongle is connected to the audio jack output available on mobile phones. It has an LED through which audio/music signals are transmitted as light signals. These light signals are captured by the Li-Fi speaker through the solar cell array.

Periodically On Off Mosquito Repellent Save Rs. 20.00

Periodically On Off Mosquito Repellent

by KNS Pvt Ltd
Save Rs. 20.00
Rs. 119.99
Rs. 99.99

Summary

Some of the mosquito repellents available in the market use a toxic liquid to generate poisonous vapors in order to repel mosquitoes out of the room. Due to the continuous release of poisonous vapors into the room, after midnight the natural balance of the air composition for good health reaches or exceeds the critical level.

Mostly, these vapors attack the brain through the lungs and exert an anesthetic effect on mosquitoes as well as other living beings by small or greater percentage. Long exposure to these toxic vapors may cause neurological or related problems.Here is a circuit that automatically switches on and off the mosquito repellent after a preset time interval, thus controlling the release of toxic vapors into the room.

Learning

Things which you can learn:

*Application of NE 555 timer.
*Application of TRIAC BT136.
*Application of Zener diode as a voltage regulator.

Product Description

Here is a circuit that automatically switches on and off the mosquito repellent after the preset time interval, thus controlling the release of toxic vapours into the room. The circuit turns the mosquito repellent ‘on’ for approximately 20 minutes then process of 'on' and 'off' occurs repeatedly.So if you leave the mosquito repellent switched on from 10 pm to 6 am (eight hours), it will be ‘on’ for four hours and ‘off’ for four hours of the total duration. During ‘off’ time, the room air tries to balance its natural composition.

Another important feature is that the circuit switches to ‘on’/‘off’ operation without producing any noise or a sound click as in a relay and hence doesn’t disturb your sleep.

Working

The circuit consists of a timer section built around IC 555 (IC1) and an automatic switching section using Triac BT136 (triac1). Power supply to the circuit is derived from the AC mains by stepping it down to a required level and rectifying it. The elimination of the transformer saves on space as well as money. Zener diode ZD1 and capacitor C2 provide regulated 9V DC power supply to timer IC1.The timer section comprises resistors R1 and R2 and capacitor C1.

The output of timer IC 555 is fed to the gate terminal of BT136 through series LED1 and resistor R4. When the timer output goes high, it triggers the gate of Triac 1 and LED1 shows the ‘on’ period. During ‘off’ time, the output of IC1 goes low and hence Triac 1 is not fired and LED1 doesn’t glow. The circuit is very compact and can be assembled on a general-purpose PCB. Use an 8-pin IC base for timer IC LM555. After assembly, fit the unit inside the housing electric board where you plug in the mosquito repellent.

 

Click here to Download PDF

 

Numeric Water Level Indicator with Display Save Rs. 75.00

Numeric Water Level Indicator with Display

by KNS Pvt Ltd
Save Rs. 75.00
Rs. 300.00
Rs. 225.00

Summary

Most water level indicators are equipped to indicate and detect only a single level. The Numeric Water Level Indicator implemented here can indicate up to nine such levels and displays the level no. on a seven segment display. Hence, not only is the circuit capable of cautioning a person that the water tank has been filled up to a particular level, it can also indicate that the water level has fallen below the minimum level.

This is particularly important in appliances such as the desert cooler where there is a danger of motor-burnout when the water is used up. This circuit exploits the simple fact that water is a good conductor of electricity. The placement of nine probes (having connections to the circuit) at different heights inside the water tank determines the nine different detectable levels. When the water reaches a particular height in the tank; the seven segment display shows the corresponding level no., digit 9 representing the “tank full” condition and digit 0 representing the “tank empty” condition.

Learning

Things which you can learn:


*Application of the Priority Encoder IC 74HC147
*Application of the BCD to Seven Segment Decoder IC CD4511 (for driving seven segment displays).

Product Description

The Numeric Water Level Indicator employs a simple mechanism to detect and indicate the water level in a tank or any other container. The level sensing is done by a set of nine probes which are placed at nine different levels on the tank walls (with probe9 to probe1 placed in decreasing order of height, COM probe is placed on the base of the tank). Basically, level9 represents the “tank full” condition while COM represents the “tank empty” condition.

Working

When the tank is empty, all the inputs to the priority encoder 74HC147 (IC1) remain high, as a result its output also remains high. Since these outputs are inverted and fed as inputs to the decoder driver CD4511 (IC2), all inputs to IC2 are low.

The seven segment display correspondingly shows the digit 0, indicating that the tank is empty.

When the water reaches level1 (but is below level2), pin11 (A0) of IC1 is pulled to ground and the output generated at pin9 (Y0) of IC1 also becomes low. After inversion, the bits fed to the input pins of IC2 are 0001 (DCBA). Hence, the corresponding digit displayed by the seven segment display is 1. The similar mechanism applies to the detection of all the other levels.
When the tank is finally full, all inputs to IC1 become low and all its outputs also go low. This causes all the inputs to IC2 to go high and hence the display shows a 9, thereby indicating a “tank full” condition.

 

Click here to Download PDF

 

Fastest Finger First Indicator Save Rs. 25.00
Rs. 400.00
Rs. 375.00

Fastest Finger First Indicator

Fastest Finger First Indicator

by KNS Pvt Ltd
Save Rs. 25.00
Rs. 400.00
Rs. 375.00

Summary

Build a Fastest Finger First Indicator with this simple kit interactive and use it in a quiz and game shows for indicating which player reacted or answered the fastest. The number assigned to the player is displayed by the circuit along with an alarm sound while the fastest finger buttons of the other contestant are locked.

Learning

Things Which you will Learn :

*Basics and implementation of Priority Encoder IC 7475.
*Concept and implementation of Latch
*Basics and implementation of hex inverter gates with IC 74LS04
*Concept of Binary Coded Decimal and BCD to 7 segment display IC 7447
*Concept and implementation of Frequency oscillator with NE555 IC

Product Description

The Fastest Finger First Indicator circuit determines as to which of the four contestants pressed the button first and locks out the entries from the remaining three contestants. Simultaneously, an audio alarm and the correct decimal number display of the corresponding contestant are activated.

Working


When a contestant presses his switch, the corresponding output of the latch IC 7475(IC2) changes its logic state from 1 to 0. The combinational circuitry comprising dual 4-input NAND gates of 7420 (IC3) locks out subsequent entries by producing the appropriate latch-disable signal. Priority encoder IC 74147(IC4) encodes the active-low input condition into the corresponding binary coded decimal (BCD) number output. The outputs of IC4 after inversion by inverter gates inside hex inverter 74LS04 (IC5) are coupled to BCD-to-7-segment decoder/display driver 7447(IC6). The output of IC6 drives common common-anode 7-segment LED display (DIS.1, FND507 or LT543).

The audio alarm generator comprises of the frequency oscillator NE555 (IC7), whose output drives a loudspeaker. The oscillator frequency can be varied with the help of preset VR1. Logic 0 state at one of the outputs of IC2 produces logic 1 input condition at pin 4 of IC7, thereby enabling the audio oscillator.
IC7 needs +12V DC supply for sufficient alarm level. The remaining circuit operates on regulated +5V DC supply, which is obtained using IC1 (7805). Once the organizer identifies the contestant who pressed the switch first, he disables the audio alarm and at the same time forces the digital display to ‘0’ by pressing reset push button S5.

Click To View Circuit Diagram

Click here to Download PDF

Remote Control for Home Appliances Save Rs. 50.00

Remote Control for Home Appliances

by KNS Pvt Ltd
Save Rs. 50.00
Rs. 325.00
Rs. 275.00

Summary

The Remote Control for Home Appliances can be used to switch ON and OFF any home appliance or electrical device with a single press of a TV/VCR/DVD remote control. This low-cost circuit is based on the CD4017 counter IC which receives trigger pulse from the IR sensor and switches ON the relay, through which electrical devices are switched ON. Upon receiving the 2nd pulse the device is switched OFF.

Get ready to control your home appliances from your TV Remote control and upgrade your home to a techie Palace!!

Learning

Things which you can learn:
*Application of the IR transmitter and receiver modules.
*Application of the decade counter IC CD4017.
*Use of relays to drive loads.
*Applications of Transistors as amplifiers

Product Description

The Remote Control for Home Appliances can be connected to many home appliances such as lamps, fans, radios, etc to make the appliance switch ON/OFF from a TV, VCR or DVD remote control. This circuit can be operated from upto 10 meters.

Working


The 38kHz infrared (IR) rays generated by the remote control are received by IR receiver module TSOP1738 of the circuit. The output signal (from pin3) is amplified by transistor T1 (BC558). This amplified signal is fed to the clock pin (pin no.14) of decade counter IC CD4017 (IC1), pin 3 of which is connected to a red LED (LED1). This LED glows to indicate that the appliance is OFF. The output (pin no.2) of IC1 is connected to a green LED (LED2) and is used to indicate the ON state of the appliance. Transistor BC548 (T2) is connected to pin 2 of IC1 and drives the relay RL1.

The appliance to be controlled is connected between the pole of the relay and neutral terminal of mains. It gets connected to live terminal of AC mains via normally opened (N/O) contact when the relay energizes.

Click To View Circuit Diagram

Click here to Download PDF

Moisture Monitor For Plants Save Rs. 50.00
Rs. 300.00
Rs. 250.00

Moisture Monitor For Plants

Moisture Monitor For Plants

by KNS Pvt Ltd
Save Rs. 50.00
Rs. 300.00
Rs. 250.00

Summary

The circuit is based on CD4060 14 Stage binary ripple counter which provides a frequency at pin 7 of the CD4060 which is decreased at pin 4 and gives a train of pulses for the transistor to switch the buzzer

Learning

CD4060 is a ripple counter IC which is widely used in digital electronics and this circuit teaches a concept which can be used to innovate new circuits based on CD4060

Product Description

Over-watering and under watering both are harmful to plants. Roots need air as well as water. If the soil is constantly saturated, air cannot reach the roots and they suffocate. Also, excess water weakens the plant and makes it susceptible to various diseases, particularly fungal attacks. Underwatering, on the other hand, is equally harmful. Plants not receiving enough water drop from the top down and leaf edges turn brown. Moisture monitor provides a solution to the above problem by monitoring the moisture level of the soil and producing an audio visual alert when the moisture goes below a preset level, indicating that the plant needs to be watered.

Click To View Circuit Diagram

Click here to Download PDF

Sunset Lamp
Rs. 100.00

Sunset Lamp

Sunset Lamp

by KNS Pvt Ltd
Rs. 100.00

Summary

This kit is based on the principle of Light dependent resistor . Thus when the sun sets the ambient light in the environment decreases and thus the light glows up.

Learning

Things which you will learn:

*Application of NE555 in bi stable mode.
*Concepts related to the working of Light Dependent Resistors.
*Application of TRIAC BT136.
*Application of Zener Diode.

Product Description

Build this automatic sunset light , which will light up when its dusk and will help in conserving electricity .

Working

The circuit uses popular timer IC NE555 as a Schmitt trigger to give the bistable action. The set and reset functions of the comparators within the NE555 are used to give the instantaneous action. The upper threshold comparator of IC1 trips at 2/3Vcc, while the lower trigger comparator trips at 1/3Vcc.The inputs of both the threshold and the trigger of NE555 are tied together and connected to the voltage divider formed by LDR1 and
VR1. The voltage across LDR1 depends on the light intensity.

In daylight, LDR1 has low resistance and the input voltage to the threshold comparator goes above 2/3Vcc and its output becomes zero, and the lamp remains off.
At sunset, the resistance of LDR1 increases, and the voltage at the input of the threshold comparator decreases below 2/3Vcc and that of the trigger comparator goes below 1/3Vcc. As a result, the outputs of threshold and trigger comparators go high. Thus it completes the power supply to the lamp through triac1. LED1 glows to indicate the high output state.

 

Click here to Download PDF

 

Cordless FM MIC Save Rs. 50.00
Rs. 200.00
Rs. 150.00

Cordless FM MIC

Cordless FM MIC

by KNS Pvt Ltd
Save Rs. 50.00
Rs. 200.00
Rs. 150.00

Summary

The Cordless FM Mic can be used as an FM transmitter. The frequency transmitted by the circuit is FM modulated and hence the voice at condenser microphone can be listened to through a standard FM receiver.

Learning

Things which you can learn:

*Concepts related to FM modulation and transmission.
*Application of NPN transistors as signal amplifiers.
*Application of the condenser mic as an input device.

Product Description

Build a simple circuit which can be used as a one-way walkie talkie. Use this kit to transmit your voice over FM and receive the sound in a standard FM receiver.

Working

The circuit of the Cordless FM Mic consists of a high-frequency air core coil (L1) with six closely wound turns of 25 SWG enameled copper wire on 4 mm diameter air former. The range of this transmitter can be enhanced by connecting a 30-60cm long wire as an antenna and changing the value of the 0.0015 micro Farad capacitor to up to 33 Pico Farad.

The range and transmitted frequency can be changed by increasing or decreasing the length of wire which is connected to a collector of NPN transistor 2N2369 (T2)via a capacitor. NPN transistor BC548 (T1) works as a condenser mic amplifier and T2 works as an FM oscillator and modulator by the help of other passive components. The main advantage of this transmitter is that it works off a 3V battery which can be easily obtained from two AA size pencil batteries.

Click To View Circuit Diagram

Click here to Download PDF

Speed Checker For Highways

Speed Checker For Highways

by KNS Pvt Ltd
Rs. 650.00

Summary

While driving on highways, motorists tend to exceed the maximum permissible speed limit set by the traffic department. The speed checker implemented here is a low cost solution which will allow the traffic policemen to monitor speeds. The Speed Checker for Highways displays a digital reading corresponding to the vehicle’s speed and also sounds an alarm if the vehicle exceeds the permissible speed for the highway.


The speed-sensing is done by the means of two laser transmitter-LDR sensor pairs. These are installed on the highway 100 meters apart, with the transmitter and the LDR sensor of each pair on the opposite sides of the road. The system displays the time taken by the vehicle to cross this 100m distance from one pair to the other with a resolution of 0.01 second. The speed of the vehicle can be calculated from the simple speed-time-distance equation.

Learning

*Application of the NE555 timer in the monostable and astable mode.

*Application of the decade counter/7-segment decoder IC CD4026.

Product Description

The Speed Checker Kit for Highways is a simple kit based on 555 Timer IC, NAND gate inverter, Decade counter and 7 segment display to calculate the speed of vehicles , plying on the road.


Working


The Speed Checker for Highways implemented here assumes that the maximum permissible speed for highways is either 40Kmph or 60Kmph as per the traffic rule. For 40kmph limit the time period is set for 9 seconds using preset VR1, while for 60kmph limit the time period is set for 6 seconds using preset VR2. Slide switch S1 is used to select the time period as per the speed limit i.e. either 40Kmph or 60Kmph. The junction of LDR1 and resistor R1 is coupled to pin2 of IC1. Normally, light from the laser keeps falling on the LDR sensor continuously and thus the LDR offers a low resistance and pin2 of IC1 is high.


Whenever light falling on the LDR is interrupted by any vehicle, the LDR resistance goes high and hence pin 2 of IC1 goes low to trigger the monostable. As a result, output pin3 goes high for the preset period, either 9 or 6 seconds, and LED1 glows to indicate it. Reset pin 4 is controlled by the output of NAND gate N3 at power-on or whenever reset switch S2 is pushed. For IC2, the monostable is triggered in the same way as IC1 when the vehicle intersects the laser beam incident on LDR2 to generate a small pulse for stopping the count and for use in the speed detection. LED2 glows for the duration for which pin 3 of IC2 is high.


The outputs of IC1 and IC2 are fed to input pins 2 and 1 of NAND gate N1, respectively. When the outputs of IC1 and IC2 go high simultaneously i.e. the vehicle has crossed the preset speed limit, output pin 3 of gate N1 goes low to trigger mono-stable timer IC3. The output of IC3 is used for driving piezoelectric buzzer PZ1, which alerts the operator of speed-limit violation.


Resistor R9 and capacitor C5 decide the time period for which the piezoelectric buzzer sounds. The output of IC1 triggers the bistable (IC4) through gate N2 at the leading edge of the count-start pulse. When pin2 of IC4 goes low, the high output at its pin 3 enables astable clock generator IC5. Since the count-stop pulse output of IC2 is connected to pin6 of IC4 via diode D1, it resets clock generator IC5. IC5 can also be reset via diode D2 at power-on as well as when reset switch S2 is pressed.

Click To View Circuit Diagram

 

 

Click here to Download PDF


 

 

Smoke Alarm Save Rs. 25.00
Rs. 200.00
Rs. 175.00

Smoke Alarm

Smoke Alarm

by KNS Pvt Ltd
Save Rs. 25.00
Rs. 200.00
Rs. 175.00

Summary

Most smoke detecting circuits available commercially, make use of expensive smoke sensors which require complicated interfacing circuitry around them. However, the Smoke Alarm implemented here is capable of detecting smoke consistently and employs a simple phototransistor optical interrupter switch as the smoke sensor. This smoke-detecting circuit utilizes the simple fact that in case smoke is present, the optical signal transmitted from the infrared emitting diode to the photo-transistor (both part of the photo interrupter module) will be interrupted. Once such a situation is encountered, an alarm sound is generated by the loudspeaker till the time smoke clears. Number of ICs used: 1.

Learning

Things Which you can learn:
*Application of the phototransistor optical interrupter switch H21A1
*Implementation of the astable mode of the NE555 timer IC.

Product Description

The smoke alarm circuit employs a simple mechanism to detect smoke in the vicinity and sound an alarm. The sensing is done by the photo-transistor optical interrupter switch while the alarm is sounded by the NE555 timer IC, the output of the former acts as the input of the latter.

Working

In the absence of any smoke, the gap of the photo-transistor interrupter housing is clear and the infrared light from the diode falls directly onto the photo-transistor. This keeps the photo-transistor of the optical interrupter module in saturation. Owing to this, the reset pin (active LOW) of the NE555 IC is pulled to ground and it continuously resets the NE555 timer IC. No output is generated at pin3 and hence the loudspeaker does not sound an alarm.

In case of smoke, the gap between the diode and the photo-transistor gets clouded with smoke and the optical signal is interrupted. (The threshold value of the least detectable smoke density is decided by the variable resistor VR1). This interruption in the optical signal causes the base voltage of photo-transistor to fall and cut-off. As a result, the collector terminal of the photo-transistor as well as the reset pin (pin no.4) of the NE555 IC is held high via resistor R2. Hence, oscillations are generated at the output pin (pin no.3) of the NE555, the frequency of which is decided by the value of R3, R4 and C1. This electrical signal (oscillations) is input to the loudspeaker through the capacitor C3 and is further converted into a loud and continuous alarm sound.

Click To View Circuit Diagram

Click here to Download PDF

Door Guard Save Rs. 50.00
Rs. 300.00
Rs. 250.00

Door Guard

Door Guard

by KNS Pvt Ltd
Save Rs. 50.00
Rs. 300.00
Rs. 250.00

Thieves often target locked houses. This door guard circuit detects any vibration in its vicinity when somebody tries to break open the door. A simple circuit to protect all your valuable things.

Learning from this project

Things which you can learn:

  • Application of UM3561 IC.
  • Working of the transistor as an amplifier.
  • Working of MOSFET BS170.
  • Application of piezoelectric sensor.

Product Description

This is a simple door guard circuit which is based on piezo electric sensor to detect changes in the vibration caused due to the opening of doors.

Project working

The heart of the circuit is the piezo transducer (PZ1), which is the sensor element. If anyone attempts to open the door, the piezo element vibrates and the developed voltage drives transistors T1 and T2 into conduction. Then the alarm sounds for 20 seconds, which is taken care of by MOSFET T3 along with capacitor C1 and resistor R4 wired as a monostable timer.

 

Click here to Download PDF

Burglar Alarm Save Rs. 25.00
Rs. 150.00
Rs. 125.00

Burglar Alarm

Burglar Alarm

by KNS Pvt Ltd
Save Rs. 25.00
Rs. 150.00
Rs. 125.00

Summary

The burglar alarm implemented here is a simple circuit that automatically sounds an alarm whenever an intrusion is detected. The system is implemented by installing a simple sensing loop, which is basically a thin copper wire. This way, the loop is both invisible and brittle enough to break easily and initiate the alarm mechanism.

At the time of an intrusion, the loop breaks and this causes the loudspeaker to generate a continuous and loud alarm sound. Once the loop is broken, the alarm can only be silenced by either turning OFF the power supply or by replacing the broken wire by a new continuous loop. Number of ICs used: None

Learning

Things which you can learn:

*Operation of transistors (both NPN and PNP type) in different modes, especially in conduction and cut-off mode.
*Two stage amplifier with feedback.

Product Description

The Burglar Alarm circuit employs a simple mechanism to sound an alarm when an intrusion is detected. If the loop is broken then an intrusion is detected and the alarm is sounded.

Working

It consists of an oscillator section which is merely a two-stage amplifier with feedback. This amplifier is implemented with the help of two transistors (T1 is an NPN transistor-BC548 while T2 is a PNP transistor-SK100) connected in a feedback arrangement to generate oscillations. Transistor T1 is responsible for generating oscillations while transistor T2 (connected to the base of T1) amplifies these oscillations in order to drive the loudspeaker for sounding the alarm.

Consider the following cases:

1. Secure Premises: The connection of the two transistors is such that the base of T1 is normally shorted to the ground and that it remains in the cut-off mode when the sensing loop is intact. Due to the absence of the base current in T1 in this mode, there are no oscillations and hence, the loudspeaker does not generate the alarm sound. This indicates that no intrusion has taken place.

2. Intrusion: When the loop is broken by an intruder or a burglar, the base of transistor T1 becomes open and oscillations are generated at its collector. As the base of T2 is connected to the collector of T1, the oscillations are amplified by it and further fed back to its emitter (via the path along capacitor C1 and resistors R1, R2). The loudspeaker obtains this amplified signal from the collector of transistor T2 and converts it into audible alarm sound. This indicates the occurrence of an intrusion/break-in.

As both the transistors are silicon type, the current drawn by the circuit is very low even in the alert mode.

 

Click here to Download PDF

 

Automatic Night Lamp Dimmer with Morning Alarm Save Rs. 75.00

Automatic Night Lamp Dimmer with Morning Alarm

by KNS Pvt Ltd
Save Rs. 75.00
Rs. 300.00
Rs. 225.00

This automatic night lamp serves a dual purpose, depending on the intensity of light rays detected. The circuit is capable of automatically switching ‘ON’ a white LED on detecting darkness, to act as a night lamp. Conversely, it can also sense daylight and play a melodious tune as a morning alarm. The circuit operates on AC supply and the circuit also provides for battery backup in case of power failure.

No. of ICs used: 3

Learning from this project

  • Application of NE555 timer IC in monostable mode.
  • Concepts related to the working of light dependent resistors.
  • Implementation of bridge rectifier circuit for AC to DC conversions.
  • Application of the music generator IC UM66.

Product Description

This project builds an automatic lamp with night dimmer and morning alarm. It can set the ambient light of your room and also wake you up when the sun rises.

Working

The automatic night lamp dimmer with morning alarm is powered by a standard 0-9V transformer. Diodes (D1-D4) rectify the AC voltage and the resulting DC voltage is smoothed by a capacitor (C1). Voltage regulator IC (7806) provides regulated 6V DC supply to the circuit while battery backup is also provided to power the circuit when mains fails. When mains supply is available, a 9V rechargeable battery charges via a diode (D5) and a resistor (R1) with a reasonably constant current. In the event of a power failure, the battery automatically takes up the load without delay.

The circuit uses light dependent resistors (or LDR) for sensing ambient light conditions. Typically, an LDR offers high resistance in darkness, which reduces to a minimum when bright light is incident on it. In this automatic night lamp dimmer circuit, one LDR (LDR1) detects darkness while another LDR (LDR2) detects light in the morning.

The circuit is designed around the single timer IC NE555 (IC2), which is configured to work in the monostable mode in the circuit. IC2 is activated by a low pulse applied to its trigger input (pin 2). Once triggered, the output pin (pin 3) of IC2 goes high and remains in that position until IC2 is triggered again by the input at pin 2. When LDR1 is illuminated by the ambient light, its resistance falls to a minimum and pin 2 (trigger input) of IC2 remains at a positive potential. This causes the output (pin 3) of IC2 to go low and hence, the white LED remains off.

In absolute darkness, the LDR has a resistance in excess of 280-kilo ohms. So, when the resistance of LDR1 increases, a short pulse is applied to trigger input (pin2) of IC2 via a resistor (R2).

This triggers the monostable mode of operation and the output pin of the NE555 (IC2) goes high, causing the white LED to glow. A low-value capacitor (C2) maintains the monostable for continuous operation, eliminating the timer effect. By increasing the value of C2, the ‘ON’ time of the white LED can be adjusted. LDR2 and associated components generate the morning alarm at dawn. LDR2 detects the ambient light in the room at sunrise and its resistance gradually falls. This makes a transistor (T1) to start conducting. When T1 conducts, a melody-generator IC UM66 (IC3) gets supply voltage from the emitter of T1 and it starts producing the melody. A single-transistor amplifier (T2) amplifies the musical tone generated by IC3.

Click To View Circuit Diagram

Click here to Download PDF

6 in 1 Gift Box Save Rs. 101.00
Rs. 700.00
Rs. 599.00

6 in 1 Gift Box

6 in 1 Gift Box

by KNS Pvt Ltd
Save Rs. 101.00
Rs. 700.00
Rs. 599.00

The Gift box contains 5 electronic project kits and a soldering kit to make them. Gift Box has one each of the following kits;

  • Musical Touch Bell
  • Musical Door Bell
  • Water Level Indicator
  • Burglar Alarm
  • Magic Eye
  • Soldering Kit

Learning from the kit

Things you can learn,

  • Application of the melody generator IC BT66 (or UM66).
  • Application of PNP and NPN type transistors for switching purposes.
  • Application and implementation of the NE555 timer IC in the astable mode.
  • Principle involving the use and function of LDRs (Light Dependent Resistors) and their application.
  • Hands on experience of soldering different components.

Product Description

The 6 in 1 gift box is a complete kit for those keen on developing quality electronic projects. It contains 5 projects which test your skills at a different level. It also contains a soldering kit required to complete this kit. This box opens up a great opportunity for learning.

Musical Touch Bell: The Musical Touch Bell implemented here can be operated by just bridging the gap between two touch plates by one’s fingertips and requires minimal power consumption. The circuit generates a pleasant musical tone through a melody generator IC, as long as the touch plates are in contact.

Musical Door Bell: Most conventional doorbells available in the market generate alarm for a specific time duration which cannot be reprogrammed or controlled. This can be annoying when a person has answered the door immediately. The musical doorbell (with memory) implemented here is a simple doorbell whose ringing duration can be varied easily. The circuit generates a pleasant musical tone for a preset time duration after the toggle switch is pressed.

Water Level Indicator: The purpose of a water level indicator is to caution when a water tank has been filled up to a particular level. This circuit exploits the simple fact that water is a good conductor of electricity. The system is capable of indicating the water level in two ways- visual (by the means of an LED) and audible (by the means of a sound generated by a piezoelectric buzzer).

Burglar Alarm: The burglar alarm implemented here is a simple circuit that sounds an alarm on detecting intrusion. The system is implemented by installing a simple sensing loop, which is basically a thin copper wire. This way, the loop is both invisible and brittle enough to break easily and initiate the alarm mechanism. At the time of an intrusion, the loop breaks causing the loudspeaker to generate a continuous and loud alarm sound.

Magic Eye: It can be used for a variety of applications like a burglar alarm, smoke detector or an automatic guest indicator. All these applications make use of the Light Dependent Resistor (LDR) which is installed and implemented differently in each case.

Soldering Kit-Contains basic tools for soldering.

Cellphone Detector Mobile Bug Save Rs. 50.00
Rs. 300.00
Rs. 250.00

Cellphone Detector Mobile Bug

Cellphone Detector Mobile Bug

by KNS Pvt Ltd
Save Rs. 50.00
Rs. 300.00
Rs. 250.00

Summary

This handy, pocket-size mobile transmission detector can sense the presence of an activated mobile phone from distance of one and- a half meters. So it can be used to prevent the use of mobile phones in examination halls, confidential rooms, etc. It is also useful for detecting the use of mobile phone for spying and unauthorized video transmission.

Learning

Things which you can learn:

*Working of CA3130 as current to voltage converter.
*Application of transistor as an amplifier.
*Application of NE555 as an amplifier.

Product Description

Build yourself a mobile detecting bug and become an expert in finding out hidden mobile phones in sensitive areas like LPG godown etc.

Working:

The circuit can detect both the incoming and outgoing calls, SMS and video transmission even if the mobile phone is kept in the silent mode.The circuit uses a 0.22μF disk capacitor (C3) to capture the RF signals from the mobile phone.The disk capacitor along with the leads acts as a small gigahertz loop antenna to collect the RF signals from the mobile phone.

Op-amp IC CA3130 (IC1) is used in the circuit as a current-to-voltage converter with capacitor C3 connected between its inverting and non-inverting inputs.

When the mobile phone signal is detected by C3, the output of IC1 becomes high and low alternately according to the frequency of the signal as indicated by LED1. This triggers monostable 555timer.

 

Click here to Download PDF

“What’s Included In This Box”.

 

S.No Component Quantity
1   Capacitor 22pF ceramic 2
2   Capacitor 0.22uF ceramic 1
3   Capacitor 100uF 25V electrolytic 1
4   Capacitor 47pF ceramic 1
5   Capacitor 0.1uF ceramic 2
6   Capacitor 0.01uF ceramic 1
7   Capacitor 4.7uF 25V electrolytic 1
8   IC CA3130 1
9   IC NE 555 1
10   LED RED 1
11   Piezzo Buzzer 1
12   Resistor 2.2M 2
13   Resistor 100K 1
14   Resistor 1K 1
15   Resistor 12K 1
16   Resistor 15K 1
17   Tr BC548 1
18   switch on/off 1
19   8-pin base 2
20   Antenna 1
21   PCB - AB4380 - Cell Phone Detector 1

 

Water level Indicator

Water level Indicator

by KNS Pvt Ltd
Rs. 100.00

Summary

The purpose of the water level indicator is to caution a person that a water tank has been filled up to a particular level. This circuit exploits the simple fact that water is a good conductor of electricity. The system is capable of indicating the water level in two ways- visual (by the means of an LED) and audible (by the means of a sound generated by a piezoelectric buzzer).

The placement of two probes (with connections from the circuit) inside the water tank determines the minimum detectable level (MDL). When the water reaches this height in the tank (or any other fluid container), the buzzer is activated and the LED is turned on. Number of ICs used: None.

Product Description

The water level indicator employs a simple mechanism to detect and indicate the water level in a tank or any other container. The level sensing is done by a pair of probes, the resistance between which depends upon the water level in the tank. These probes can be placed in two ways on the walls of the tank or container.

Working

1. Both the probes can be placed at different points on the wall lying at the same level/height from the bottom. This height determines the minimum detectable water level, or

2. The probes can be placed at different points lying at two different heights from the tank bottom. In this case, the probe which is placed higher than the other determines the minimum detectable water level.

When the water-level is below the minimum detectable level (MDL), there is infinite impedance between the two probes. Hence, transistor T2 remains in the cut-off mode and does not conduct. However, when water-level reaches MDL or is above it, the connection between the probes gets completed (through the conducting medium o water) and the base voltage of T2 increases.

This causes the base-emitter junction of T2 to get forward biased and the piezoelectric buzzer is turned on to generate an alarm sound. The path from the emitter of T2 through resistance R3 is responsible for forward biasing the base of transistor T1. This switches T1 from cut-off to conduction mode, thereby driving the red LED to glow. Hence at each instance when water reaches the MDL, both the buzzer and LED indicate this simultaneously.

 

Click here to Download PDF

 

Noise Level Alarm Save Rs. 50.00
Rs. 300.00
Rs. 250.00

Noise Level Alarm

Noise Level Alarm

by KNS Pvt Ltd
Save Rs. 50.00
Rs. 300.00
Rs. 250.00

Summary

Noise pollution can cause hearing loss, hypertension, heart disease, annoyance, sleep disturbance and decreased performance in schools. Build this kit and set the threshold level for the noise and get informed whenever the sound gets exceeded the desired limit and thus prevent damage to the health.

Learning

Noise level monitoring gives a brief hands on concept of cascaded and three stage amplifiers in analog electronics and amplifying a very small signal with high gain transistors

Things which you can learn:
1. Cascaded three stage amplifier
2. Analog electronics
3. Gain in transistors
4. Condensor mic

Product Description

Noise is a serious environmental problem that affects us in our daily life. There is scientific evidence supporting that noise exposure can cause hearing loss, hypertension, heart disease, annoyance, sleep disturbance and decreased performance in schools. Sound-level indicators like the one presented here can help address this problem. This sound-level indicator monitors the sound level and indicates through an LED when the level is above the preset value.

Working

The sound is captured by microphone MIC1 and amplified by first stage high-gain transistor T1. Trimmer potentiometer VR1 is used to adjust the threshold level. the signal is amplified again with second-stage transistor T2. This amplified signal is rectified by diode D1 and the charge is stored in capacitor C10. Diode D1 should preferably be a small-signal Schottky diode such as BAT81, BAT82, BAT83, BAT85 or better. You can use 1N4148 and 1N914 also but the signal from the input should be stronger.

Click To View Circuit Diagram

Click here to Download PDF

Electronic Bicycle Lock Save Rs. 75.00
Rs. 300.00
Rs. 225.00

Electronic Bicycle Lock

Electronic Bicycle Lock

by KNS Pvt Ltd
Save Rs. 75.00
Rs. 300.00
Rs. 225.00

The electronic bicycle lock is a worthwhile alternative for bicycle owners who want to make their bicycles ‘intelligent’ at a reasonable cost. The circuit can be used for any make of bicycles.

Learning

Things which you can learn:

*Application of the tone generator IC UM3561.
*Basics of RCA sockets.

Product Description

Now build yourself a cool Bicycle lock based on the simple concept of loop breaking and prevent bicycle theft.

Working


In the Electronic Bicycle Lock circuit, input jacks (J1 and J2) which are two standard RCA sockets are used. A security loop (made in-house) is used to link these two input points, it is about 50cm long and is a basically a standard 14/36 flexible wire with one RCA plug per end. The circuit of the Electronic Bicycle Lock is powered by a compact 9V battery (6F22). Key lock switch S1 and smoothing capacitor C2 are used for connecting the power supply. When the loop is connected, UM3561 (or IC1) remains deactivated and therefore the speaker does not sound. When the loop is broken, zener diode ZD1 (3.1V) receives operating power supply through resistor R2 and enables the tone generator UM3561 (IC1). IC1 remains enabled until power to the circuit is turned off using switch S1 or the loop is re-plugged through J1 and J2.

 

Click here to Download PDF

 

Automatic School Bell Save Rs. 50.00
Rs. 300.00
Rs. 250.00

Automatic School Bell

Automatic School Bell

by KNS Pvt Ltd
Save Rs. 50.00
Rs. 300.00
Rs. 250.00

This automatic school bell finds use in educational institutes, factories and organizations where accurate time keeping and bell timings are necessary. This circuit automatically sounds an alarm 8 times, at intervals of 45 minutes each. After 4 intervals, a 30-minute lunch break or recess is also timed/belled for.

No. of ICs used : 4

Learning from the project

  • Application of decade counter IC CD4017.
  • Application of the AND gate IC CD4081 for logic conversion. 
  • Application of the NE555 timer IC in the astable mode of operation. 
  • Application of relays and SCRs for switching operations.

Product description

Time keeping has been an integral part of educational institutions and big factories. Build this kit which will automatically ring, at preset times, to inform students and employees. This is a simple automation project which you can bring to your school.

Circuit operation

To begin time keeping and initiate the bell mechanism using the automatic school bell circuit, the peon needs to momentarily press switch S1 to mark the beginning of the first period. Thereafter, the bell sounds every 45 minutes to indicate the end of consecutive periods, except immediately after the fourth period, when it sounds after 30 minutes to indicate the completion of lunch break. When the last period is over, LED2 glows to indicate that the bell circuit should now be switched off manually. In case the peon has been late to start the school bell, the delay in minutes can be adjusted by advancing the time using switch S3. Each push of switch S3 advances the time by 4.5 minutes. If school closes early, peon can turn the bell circuit off by momentarily pressing switch S2.

The bell circuit contains timer IC NE555 (IC1), two CD4017 decade counters (IC2 and IC3) and an AND gate CD4081 (IC4). The NE555 (IC1) is wired as an astable multi-vibrator whose clock output pulses are fed to IC2. IC2 increases the time periods of IC1 (4.5 and 3 minutes) by ten times to provide a clock pulse to IC3 every 45 minutes or after 30 minutes, respectively. When the class periods are going on, the outputs of an IC3 switch on transistors T1 and T2 via diodes D4 through D12.

Resistors R4 and R5 connected in series to the emitter of NPN transistor T2 decide the 4.5-minute time period of IC1. The output of IC1 is further connected to pin 14 of IC2 to provide a period with a duration of 45 minutes. Similarly, resistors R2 and R3 connected in series to the emitter of NPN transistor T1 decide the 3-minute time period of IC1, which is further given to IC2 to provide the lunch-break duration of 30 minutes. Initially, the circuit does not ground to perform its operation when a 12V power supply is given to the circuit. When switch S1 is pressed momentarily, a high enough voltage to fire silicon-controlled resistor SCR1 appears at its gate.

When SCR1 is fired, it provides a ground path to operate the circuit after resetting both decade counters, IC2 and IC3. At the same time, LED1 glows to indicate that school bell is now active. When switch S2 is pressed momentarily, the anode of SCR1 is again grounded and the circuit stops operating. In this condition, both LED1 and LED2 don’t glow. When the eighth period is over, the Q9 output of IC3 goes high. At this time, transistors T1 and T2 don’t get any voltage through the outputs of IC2. As a result, the astable multivibrator (IC1) stops working. The school bell sounds for around 8 seconds at the end of each period. One can increase/decrease the ringing time of the bell by adding/removing diodes connected in series across pins 6 and 7 of IC1.

The terminals of the 230V AC electric bell are connected to the normally open (N/O) contact of relay RL1.

Click To View Circuit Diagram

Click here to Download PDF

Anti-Theft Alarm for Vehicles Save Rs. 100.00
Rs. 400.00
Rs. 300.00

Anti-Theft Alarm for Vehicles

Anti-Theft Alarm for Vehicles

by KNS Pvt Ltd
Save Rs. 100.00
Rs. 400.00
Rs. 300.00

This anti theft alarm for vehicles is a security system for vehicles that generates a loud and continuous alarm in case any unauthorized person tries to gain access to your vehicle. As soon as a thief tries to start the ignition, the vehicle alarm is activated, leaving no option other than to flee as the alarm can be reset and turned OFF by the owner alone. Build this kit to prevent theft of your vehicle.

Learning from this project

  • Application of music generator IC UM3561
  • Application of NPN transistors for switching purposes
  • Application of SCRs for sensing and switching
  • Application of capacitors for temporary storage

Product description

The anti theft alarm for vehicles simulates a police siren whenever someone attempts to commit theft of your vehicle. The alarm sounds continuously for a few seconds even when the intruder switches off the ignition key.

Circuit working

The circuit consists of an SCR based trigger circuit and an audio alarm circuit. When the ignition key of the vehicle is switched off, the base voltage of the NPN transistor SL100 (T1) is low and it remains off. When the ignition key is switched on for starting the vehicle, a positive voltage is applied to the base of transistor T1 through diode D1, toggle switch (S2) and a resistor (R1) which slowly charges the 100 microfarad capacitor (C1). As a result, the base voltage of T1 rises.

As soon as the biasing voltage crosses cut-in voltage, T1 turns on and the SCR fires, giving 12V DC voltage to the alarm circuit. The alarm circuit is built around the music generator UM3561 (IC1) which has an inbuilt oscillator. The output from IC1 is fed to a transistor amplifier built around transistors BC548 (T2) and SL100 (T3). The circuit gives sufficient time delay to switch ON the alarm and leave the vehicle. The alarm once triggered, sounds until the toggle switch S1 is pressed to switch off the power supply.

A 220 microfarad capacitor (C2) is provided to sound the alarm even when the intruder switches off the ignition key. When the ignition key is switched off immediately, C2 discharges through a resistor R4 and keeps the alarm activated for half a minute. Reset switch (S3) is used to reset the alarm if needed.

Click To View Circuit Diagram

Click here to Download PDF

Simple Code Lock Save Rs. 100.00
Rs. 300.00
Rs. 200.00

Simple Code Lock

Simple Code Lock

by KNS Pvt Ltd
Save Rs. 100.00
Rs. 300.00
Rs. 200.00

Summary

Wow wouldn't it be cool to build yourself an electronic lock to protect your costly things? Yes we bring you the Simple Code Lock kit which is basically an electronic code lock that responds only to the right sequence of four digits that can be punched in through the nine keys available on a typical keypad. If an incorrect key is pressed, the lock gets automatically reset. This circuit can be usefully employed in cars so that the car can start only when the correct code sequence is keyed in via the key pad. The circuit can also be used in various other applications. No. of ICs used: 2

Learning

Things Which you can Learn:

*Application of the Dual D Flip-Flop IC CD4013 for logic conversion.
*Application of transistors for switching purposes.

Product Description

Enter into the Sci Fi world and build yourself an exciting Code lock based on the concept of D latch and amaze your friends

Working:

The circuit of the Simple Code Lock is built around two CD4013 Dual-D Flip-Flop ICs. The clock pins of the four flip-flops are connected to a, b, c and d pads in the circuit. The correct code sequence for energisation of relay (RL1) is realised by clocking points a, b, c, and d (in that order). The five remaining switches are connected to the reset pad which resets all the flip-flops. Touching the key pad switch a/b/c/d briefly pulls the clock input pin high and the state of flip-flop is altered.

The Q output pin of each flip-flop is wired to D input pin of the next flip-flop while D pin of the first flip-flop is grounded. Thus, if correct clocking sequence is followed then low level appears at Q2 output of IC2 which energises the relay through relay driver PNP transistor BC557 (T1). The reset keys are wired to set pins 6 and 8 of each IC. A Power-on-reset capacitor (C1) is also connected as the state of Q output is indeterminate during switch ON operation.

Click To View Circuit Diagram

Click here to Download PDF

Smart Emergency Light Save Rs. 75.00
Rs. 300.00
Rs. 225.00

Smart Emergency Light

Smart Emergency Light

by KNS Pvt Ltd
Save Rs. 75.00
Rs. 300.00
Rs. 225.00

Summary

Now you need not fear dark nights when power breaks down. Here’s a white LEDbased Emergency light that automatically turns on when the mains power supply fails.

Learning

Things which you can learn:

*Application of NE555 inastable mode.
*Application of LDR in light and dark.
*Application of bridge rectifier.

Product Description

Build an Emergency light which will automatically switch on when the power fails, thus obviating the need to search the light and switch it on manually!!

Working


The switching circuit is built around an NE555 timer (IC1), which is wired in monostable mode. When a low voltage is applied at trigger pin 2 of IC1, the timer activates and its output pin 3 goes high. It remains in that state until IC1 is triggered again at its pin 2. Light-dependant resistor LDR1 is connected between the positive supply of the battery and trigger pin 2 of IC1. Resistor R3 is connected between pin 2 of IC1 and ground. The resistance value of LDR1 remains high in the dark (at night) and low in ambient light (in daytime). This phenomenon is utilised to control the switching circuit.

The working of the circuit is simple. In daytime, when ambient light falls on LDR1, its resistance decreases to make trigger pin 2 of IC1 high. As a result, output pin 3 goes low and the LEDs(LED1 through LED7) remain off. At night (in the dark), the resistance of LDR1 increases and a low voltage is applied to trigger pin 2 of IC1. This activates the monostable and its output goes high to make all the LEDs glow.

 

Click here to Download PDF

 

Long Range Burglar Alarm Using Laser Torch Save Rs. 75.00

Long Range Burglar Alarm Using Laser Torch

by KNS Pvt Ltd
Save Rs. 75.00
Rs. 450.00
Rs. 375.00

Summary

Most laser torch based burglar alarms work in darkness only. But this Long Range Burglar Alarm can work reliably in the daytime as well to alert you about intruders and burglars. The Burglar Alarm comprises of the laser transmitter and receiver units, to be mounted on the opposite pillars of the possible entry points. Whenever anyone enters to interrupt the transmitted laser beam falling on the receiver, the buzzer in the receiver circuit sounds an alarm. No. of ICs used: 1 Note-Laser torch will not be provided by KnS.

Learning

Things which you can learn:

*Application of NPN transistors for switching purposes.
*Use of the Photo-Darlington 2N5777 for sensing purposes.
*Application of the NE555 timer IC as a multivibrator to generate oscillations of a particular frequency.

Product Description

The range of the Burglar Alarm is approximately 30 meters, which means that the transmitter and receiver units can be placed up to 30 meters apart. Since the laser torch can transmit light up to a distance of 500 meters, this range can be increased by proper orientation of the photo-transistor. However, to avoid false triggering by sunlight, the photo-transistor should be mounted in such a way that it doesn’t directly face sunlight.Build this circuit and prevent theft in your premises.

Working

The transmitter circuit is powered by 3V DC. The multi-vibrator built around NE555 timer (IC1) produces a frequency of 5.25KHz. The body of the laser torch is connected to the emitter of the NPN transistor SK100 (T1) and the spring-loaded lead protruding from inside the torch is connected to the ground.
The receiver circuit is powered by 12V DC. It uses the photo-Darlington 2N5777 (T2) to sense the laser beam transmitted from the laser torch. The output beam signals from the photo-Darlington are given to the two-stage amplifier followed by a switching circuit. As long as the laser beam falls on photo-Darlington T2, the 12V relay (RL1) remains unenergized and the buzzer does not sound. Also, the indicating LED (LED1) doesn’t glow.
When anyone interrupts the laser beam falling on photo-Darlington T2, NPN transistor BC547 (T6) stops conducting while NPN transistor SL100 (T7) is driven into conduction. As a result, LED1 glows and relay RL1 is energize to sound the buzzer for a few seconds (the alarm duration being determined by the values of resistors R15 and capacitor C10 in the circuit). At the same time, the large indication load (230V AC alarm or hooter for louder sounds or any other device for momentary indication) also gets activated as it is connected to 230V AC mains via normally opened (N/O) contact of relay RL1.

Click To View Circuit Diagram

Click here to Download PDF

Zener Diode Tester

Zener Diode Tester

by KNS Pvt Ltd
Rs. 200.00

Summary

Zener Diodes are a very important concept when it comes to the voltage regulator. To effectively control voltage it is essential that the diodes work perfectly. So we bring you a Zener Diode Tester kit which can be used to check zener diodes of 3.3V to 18V. The breakdown voltage of the unknown zener diode is indicated on the pre-calibrated dial of the potentiometer VR1. The tester can also identify the polarity of zener diodes. No. of ICs used: None

Learning

Things which you can learn:

*Concepts related to zener diodes and their application.
*Application of transistor for switching purposes.

Product Description

The power supply section of the Zener Diode Tester provides approx. 20V DC stabilized voltage to the sensor section. The sensor circuit comprises two resistors (R2 and R30, a potentiometer (VR1), a red LED and an NPN transistor BC547 (T2).

Working:

When the linear potentiometer VR1 is adjusted such that the voltage at its wiper arm (red crocodile clip) exceeds the breakdown voltage of the zener diode, the zener diode
conducts and applies the bias voltage at the base of transistor T2, which causes the red LED to light up. When the voltage at the wiper arm (red clip) is less than the breakdown voltage, the zener diode does not conduct and red LED does not glow. For calibration of the zener diode tester, initially, the pointer knob of VR1 is set towards the zero-resistance position. Short red clip of the potentiometer and black clip of the transistor and switch on the tester. The pointer knob of potentiometer VR1 is slowly rotated in a clockwise direction until LED just starts to glow.

This setting of the knob is marked on the paper dial as 0V. Now a zener diode of a known value (for example, 3.3V) is connected between both the clips (red clip to the cathode and black clip to the anode of the zener diode). The knob of potentiometer VR1 is further rotated in the clockwise direction until the red LED just starts to glow. This setting of the knob is marked on the paper dial as 3.3V. Likewise, the dial of potentiometer VR1 is calibrated for other values of zener diodes by connecting known zener diodes to the tester.

For testing an unknown zener diode, it is connected across the clips in correct polarity
and the knob of potentiometer VR1 is rotated until red LED1 just starts to glow. The
voltage shown by the pointer knob on the dial at this setting is the breakdown voltage
value of the zener diode under test. If the zener diode is connected in reverse polarity (red clip to the anode and black clip to the cathode), the LED glows brightly at all settings of the knob above the zero reading, indicating that the zener diode is wrongly connected. The anode and cathode terminals of rectifier diodes can also be identified in this way.


EFY Note: It is not recommended to touch the clips while testing.

 

Click here to Download PDF

 

PC based timer Save Rs. 50.00
Rs. 300.00
Rs. 250.00

PC based timer

PC based timer

by KNS Pvt Ltd
Save Rs. 50.00
Rs. 300.00
Rs. 250.00

Summary

Timers are very useful both for industrial applications and household appliances. The PC Based Timer circuit interfaces with a computer through a D25 pin male connector to switch ON/OFF a device for a particular time interval. The program of the PC Based Timer is written in C language & compiled using the Turbo C compiler. The maximum timing for which the circuit can operate a device is 18 hours. No. of ICs used: 1

Learning

Things which you will learn :

*Application of the optocoupler IC MCT2E.
*Application of the NPN transistor for switching.
*Application of diodes for freewheeling/flyback.

Product Description

The PC Based Timer uses a simple program and interface circuit to switch on/off the appliance via the relay circuit. The circuit is interfaced with the PC with a D25 pin male connector.

Working


The circuit uses the IC MCT2E(optocoupler) which isolates the PC and the relay driver circuits. The MCT2E prevents the PC from any short circuit that may occur in the relay driver circuit or appliance. The glowing of a red LED in the circuit indicates that the appliance is turned on while the NPN transistor BC548 is used as the relay driver.

The program code is written in ‘C’ language and compiled using ‘Turbo C’ compiler. When the program is run, it prompts the user to input the time duration in seconds or minutes to control the appliance.

Click To View Circuit Diagram

Click here to Download PDF

Battery Low Indicator Save Rs. 75.00
Rs. 250.00
Rs. 175.00

Battery Low Indicator

Battery Low Indicator

by KNS Pvt Ltd
Save Rs. 75.00
Rs. 250.00
Rs. 175.00

The purpose of the battery low indicator is to give a visual indication when a battery has been discharged below a certain level. This is especially crucial for re-chargeable batteries that should not be discharged below a certain voltage level. This lower voltage limit depends upon the type of the battery. The battery low indicator circuit can be typically used for 12V batteries to give an indication of the battery voltage falling below the preset value. The indication is in the form of a flickering LED.

Learning from the project

  • Application of the LM319 dual comparator for level comparison.
  • Application of the NE555 timer in astable mode of operation.

Product description

The heart of the battery low indicator circuit is the dual comparator IC LM319 (denoted as IC1) which compares the battery’s voltage to a reference voltage level. Only one of the two independent comparators that are a part of the LM319 is used in the circuit. The two inputs to this comparator are:

  1. The reference voltage, which is applied to the non-inverting input pin (4). It is held constant at approximately 1.2V by the zener diode (D1).
  2. Battery’s voltage, which is applied via a potential divider arrangement built around resistors R2, R3, and preset VR1 and fed to the inverting input pin (5).

The corresponding output is generated at pin 12 of IC1. Preset VR1 is very important as it sets the voltage level at which a visual indication of the low battery level is generated. For example: If the battery under test is of 12 V and an indication is required as soon as the battery voltage falls below 10.5 V, the voltage at the inverting input (pin 5 of IC1) should be adjusted to 1.2 V using preset VR1.

Initially, when the battery is fully charged, the voltage at the inverting input (pin 5) of IC1 is higher than the non-inverting input (pin 4- voltage level held constant at approximately 1.2 V by D1). This causes the output at pin 12 of IC1 to remain low. The reset pin (pin 4) of an NE555 timer (IC2) is connected to the output pin of IC1 and hence, a low gets applied to it correspondingly. Since the reset pin is “active low”, the NE555 is reset continuously and oscillations are not generated at its output (pin 3). As a result, LED1 does not blink.

Considering the example values, when the battery voltage falls below 10.5 V, the voltage at the inverting input (pin 4) of IC1 becomes lower than the non-inverting input (pin 5) and the output at pin 12 of IC1 goes high. This applies a “high” to the connected reset pin of IC2 (NE555 timer) and the astable multi-vibrator built around IC2 starts generating oscillations. LED1 is connected to the output pin (pin 3) of IC2 and hence blinks to indicate low battery voltage and the battery needs to be charged before further use.

 

Click here to Download PDF

 

Anti-Bag Snatching Alarm Save Rs. 100.00
Rs. 400.00
Rs. 300.00

Anti-Bag Snatching Alarm

Anti-Bag Snatching Alarm

by KNS Pvt Ltd
Save Rs. 100.00
Rs. 400.00
Rs. 300.00

This anti bag snatching alarm builds a circuit that is locked in a plug and socket arrangement in standby mode. The kit can be kept in a bag or suitcase, and simulates a police horn if someone attempts to snatch the bag. Thus, while traveling, this kit enables people to carry cash or valuables without fear. The alarm can be turned off only by the authorized person by using a hidden key.

Number of ICs used: 3

Learning from the project

*Application of the operational amplifier IC CA3140 as a comparator.
*Application of the NE555 timer IC in monostable mode.
*Use of the music generator IC UM3561.
*Use of transistors as signal amplifiers.

Product description

Build yourself an awesome anti bag snatching alarm and protect your luggage and travel care-free.

Circuit working

The circuit of the anti bag snatching alarm is designed around the operational amplifier CA3140 (IC1) configured as a comparator. The non-inverting input (pin3) of IC1 is kept at half the supply voltage (around 4.5V) by a potential divider resistor network. The inverting input (pin 2) of IC1 is kept low through the shorted plug at the socket. As a result, the voltage at the non-inverting input is higher than the inverting input and the output of IC1 is high.

The output from pin 6 of IC1 is fed to trigger pin 2 of IC NE555 (IC2) via a coupling capacitor. IC2 is configured in monostable mode. The trigger pin is held high by a resistor of 10 kilo-ohms. Normally, the output of IC2 remains low and the alarm is off. A resistor and a capacitor are connected to the reset pin of IC2 to prevent false triggering.

When there is a bag-snatching attempt, the plug connected to the circuit detaches. At this moment, the voltage at the inverting input of IC1 exceeds the voltage at the non-inverting input and subsequently, the output goes low. This sends a low pulse to trigger pin 2 of IC2 to make its output high. Consequently, the alarm circuit built around IC UM3561 (IC3) gets the supply voltage at pin 5.

Its output is fed to the base of single-stage transistor amplifier BD139 (T1) that amplifies the generated alarm signal. A loudspeaker is connected to the collector of T1 to produce the alarm. The alarm can be put off if the plug is inserted into the socket again.

Click To View Circuit Diagram

Click here to Download PDF

Variable Power Supply With Digital Control

Variable Power Supply With Digital Control

by KNS Pvt Ltd
Rs. 500.00

Summary

A Variable Power Supply with Digital Control is one of the most important and essential requirements in an electronics lab. The available power supply must provide variable outputs in steps. This circuit gives variable and fluctuation-free DC voltage as output in the range of 1.5V to 12V. No. of ICs used: 4

Learning

Things which you can learn:

*Application of the NE555 timer IC in the stable mode of operation.
*Application of the 3-terminal positive and negative voltage regulator ICs LM317 and LM7912 respectively.
*Use of the decade counter IC CD4017.
* Basics of Voltage and current control

Product Description

A variable power supply is a must for those who are looking forward to taking their project building to the next level. Armed with this system you can have a clean DC supply without spikes and it ranges from 1.5 V to 12 V. Get ready and build this kit and enjoy making projects.

Working:

The circuit of the Variable Power Supply with Digital Control is built around an adjustable 3-terminal positive voltage regulator IC LM317, CMOS decade counter IC CD4017, timer IC NE555 and 3-terminal fixed negative-voltage regulator LM7912. The AC mains supply is stepped down by transformer X1 to deliver a secondary output of 12V-0-12V AC, 1A. The output of the transformer is rectified by a full-wave rectifier comprising diodes D1 through D4.

Capacitors C1 through C4 are connected in parallel to rectifier diodes to bypass undesired spikes and provide smooth and fluctuation-free power. Capacitors C5 and C13 are used as filters to eliminate ripple. Here both negative and positive half cycles are used to obtain positive as well as negative DC output. LED1, along with current limiting resistor R1, is used for mains ‘on’ indication. Timer IC NE555 (IC1) is wired as an astable multi-vibrator. It generates clock pulses when switch S2 is pressed.

The output of IC1 is connected, via an RC network, to the clock input of counter IC CD4017 (IC2). IC CD4017 is a decade ring counter. Each of its ten outputs goes high one by one when a clock pulse is received. The outputs of IC CD4017 are connected to the bases of transistors T1 through T10, respectively. LED3 through LED11 is used here to indicate the voltage levels.

The collectors of transistors T2 through T10 are connected to presets VR1 through VR9, respectively, which are used to set the output voltage. Adjustable voltage regulator IC LM317 (IC4) develops 1.25V nominal reference voltage (VREF) between its output and the adjustable terminal. The reference voltage appears across resistor R16. When the voltage is constant, a constant current flows through one of the output-setting variable resistors (VRset, VR1 through VR9), giving an output voltage at pin 2 of IC4 as VOUT=1.25(1+VRset/R16). Presets VR1 through VR9 is adjusted to get the desired output voltage.

The collector of transistor T1 is directly connected to ADJ terminal (pin 1) of IC4, so the output voltage of IC4 will be the voltage across fixed resistor R16, which is equal to 1.25V. When switch S3 is pressed, pin3 of IC2 goes high and the output voltage becomes 1.2V. When switch S2 is pressed, the output of IC1 goes high.

As a result, the outputs of IC2 go high one by one as a ring counter. Since presets VR1 through VR9 are connected at the collectors of transistors T2 through T10, respectively, different output resistances appear between the adjustable and ground terminals of IC4, resulting in different output voltages. By using a properly calibrated digital multimeter you can easily adjust the presets to obtain 1.5V to 12V. A fixed, negative 12V DC can be obtained by using fixed, the negative-voltage regulator IC LM7912 (IC3). Thus the power supply unit can be used for circuits requiring both negative and positive DC voltages. When CD4017 is reset by pressing switch S3, the output voltage becomes 1.2V and all the voltage-indication LEDs turn off.

 

Click here to Download PDF

 

Sound Operated Timer

Sound Operated Timer

by KNS Pvt Ltd
Rs. 250.00

Summary

The Sound Operated Timer is a multi-purpose electronic switch that can be used in a number of applications. The switch gets activated by the sound of a clap when clapping is done in front of a condenser mike. This turns on the appliance connected to the relay for a specified time period, after which it is automatically turned off. No. of ICs used: 1.

Product Description

The heart of the Sound Operated Timer is the NE555 timer IC (IC1) which is being operated in the monostable mode. The condenser mike converts the incoming sound signal to electrical variations that are amplified by transistor BC149. Resistors (R1-R4) and a capacitor (C1) provides proper biasing conditions for working of T1 in the active region. The amplified signals are effectively passed by capacitor C2 to trigger input pin (pin2) of IC1. This results in momentarily pulling pin2 to a low level whenever you clap in front of the mike. IC1 generated a rectangular pulse of time duration Tm at its output pin (pin3). This time duration is decided by values of preset VR1, resistors R7, R8 and capacitor C3. Thus relay RL1 at output remains energized for this specific time duration. Rotating the preset VR1 clockwise will increase this time while rotating it in an anti-clockwise manner will result in opposite effect. Diodes D1 and D2 are used as free wheeling diodes and help in proper functioning of the relay.

Learning

Application of the NE555 timer in the monostable mode.
Use of relays for appliance switching.

Power Failure And Resumption Alarm Save Rs. 100.00

Power Failure And Resumption Alarm

by KNS Pvt Ltd
Save Rs. 100.00
Rs. 300.00
Rs. 200.00

Summary

The Power Failure and Resumption Alarm circuit sounds an alarm whenever AC supply mains fails or resumes. The circuit gives an audio-visual indication of the failure and resumption of mains power through a bi-colour LED and a piezoelectric buzzer. No. of IC used: 3

Learning

Thiings Which you can learn:
*Application of the LM556 dual timer IC in the astable and monostable mode.
*Application of PNP and NPN transistors.
*Concept and working of bi-colour LEDs.

Product Description

A simple circuit which provides Audio Visual Indication when the AC supply resumes/fails.
This is important as when the users gets informed about the power failure, he/she can judiciously use the supply from the inverter so that they are not affected due to excessive drain of battery.The heart of the Power Failure and Resumption Alarm circuit is the dual timer IC LM556. When mains is present, the bicolour LED (LED1) glows in green colour while when the mains fails it turns red.

Working:

When mains is present, the PNP transistor BC558 (T1) is in the cut-off state and therefore the bicolour LED glows in green colour. When power fails, PNP transistor T1 starts conducting and bicolour LED glows in red colour. Due to non-availability of Vcc voltage at pin 14 of LM556 (IC2), its output pin (Pin9) remains low and NPN transistor BC548 (T3) does not conduct.

However, a 4700µF capacitor (C7) holds an adequate charge and hence PNP transistor BC557 (T4) conducts and the piezoelectric buzzer (PZ1) sounds continuously for approx. eleven seconds until capacitor C7 discharges completely. When power resumes, bicolour LED glows in green colour and the buzzer beeps for approx. 14 secs.

IC LM556 outputs frequencies in the form of pulses at its pin 9. These pulses are coupled to the NPN transistor BC548 (T3), which conducts and cuts off depending on the output at pin 9 of IC2. A Red LED (LED2) is connected to pin 9 via a 270-ohm current-limiting resistor (R7) to indicate power resumption.

 

Click here to Download PDF

 

Hit Switch Save Rs. 25.00
Rs. 150.00
Rs. 125.00

Hit Switch

Hit Switch

by KNS Pvt Ltd
Save Rs. 25.00
Rs. 150.00
Rs. 125.00

Summary

This versatile hit based switch is the electronic equivalent of a switch. This circuit serves as an on/ off control for incorporation in a wide variety of electronic design.The circuit uses a Piezo electric diaphragm which when pressurized produces a small potential between its plate. This small signal is amplified and used in combination with diodes to form a voltage controlled switch.

Learning

Things which you will Learn :
*Application and basics of Hex inverter with CD4069 IC.
*Implementation of the Bridge rectifier circuit for AC to DC conversions.
*Use of transistors as signal amplifiers.
*Inverter gates with IC CD4069 (IC1)

 

Product Description

This versatile hit switch is the electronic equivalent of a conventional switch. It can be used to control the switching of a variety of electronic devices.

The circuit of the hit switch uses a piezoelectric diaphragm (piezo buzzer) as the hit sensor. A piezoelectric material develops electric polarization when strained by an applied stress. The hit sensor makes use of this property.

Working:

When you hit or knock the piezo element (hit plate) with your fingertip, a small voltage developed by the piezo element is amplified by transistor BC547 (T1). The combination of transistor T1 and the bridge rectifier comprising diodes D1 through D4 acts as a voltage-control switch. The inverter gates of IC CD4069 (IC1) together with associated components form a bistable switch.

IC CD4069 is a CMOS hex inverter. Out of the six available inverter gates, only three are used here. IC1 operates at any voltage between 3V and 15V and offers a high immunity against noise. The recommended operating temperature range for this IC is –55°C to 125°C. This device is intended for all general-purpose inverter applications.

Initially, the input of gate N1 is low, while the input of gate N2 is high. Triggering the voltage-control switch by hitting the sensor pulls the input of gate N1 to a high level and causes the bistable to toggle. The capacitor gets charged via resistor R1 and the circuit changes its state. This latch continues until the bistable switch gets the next triggering input.
Every time the hit plate receives a hit, the voltage-control switch triggers the bistable circuit.

That means every subsequent hit at the sensor will toggle the state of the switch. The red LED (LED1) connected at the output of gate N3 indicates ‘on’/‘off’ position of the switch. Relay RL1 is activated by the hit switch to control the connected load.

The circuit works off 12V DC. It can be constructed on any general-purpose PCB. For the desired results, proper connections and installation of the hit sensor are necessary. Remove the cover of the piezo buzzer and connect its two leads to the circuit. Mount the plate such that it receives the hit properly. The piezoelectric material on the plate can easily get damaged, so hit the switch gently.

Click To View Circuit Diagram

Click here to Download PDF

Intruder Alarm Save Rs. 75.00
Rs. 250.00
Rs. 175.00

Intruder Alarm

Intruder Alarm

by KNS Pvt Ltd
Save Rs. 75.00
Rs. 250.00
Rs. 175.00

Summary

The Intruder Alarm automatically activates a loud alarm whenever any unauthorized entry is attempted. Unlike other alarms, the Intruder Alarm circuitry does not need replacement of a broken loop. The alarm can be turned OFF just by the simple flick of a switch. The unit power on indication by LED is also provided here for better monitoring.
Build yourself a simple intruder alarm circuit to keep the thieves at bay!! No. of ICs used: 2

Learning

Things which you will Learn :
*Learn how to use LDR sensor.
*Application of basic gates and flip-flop and hex inverters.

Product Description

The Intruder Alarm circuit should be typically fitted to the door of your house, to sound an alarm when anyone pushes the door. This way it alarms you against thieves or intruders. The circuit primarily comprises a transmitter and receiver pair. The transmitter is fitted onto the inside of the door frame while the receiver is fitted to the door panel.

Working:

The transmitter section consists of a laser diode which is powered by a 9V battery. When the switch (S1) in the transmitter section is closed, the laser diode glows. Closing switch (S2) provides power supply to the receiver section. Light falling from the laser diode on the light-dependent resistor (LDR) in the receiver section provides base current to transistor T1 and it starts conducting. This grounds the base of the transistor (T2), so it doesn’t conduct and the alarm remains off. When somebody pushes the door, light incident on the LDR is interrupted and the transistor (T1) stops conducting since the LDR offers a high resistance in the absence of light. Transistor T2 receives base current and starts conducting. The pulse from the emitter of transistor T2 is conn