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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.
Things Which you will learn:
*Application of the octal latch IC 74LS3737.
*Use of SCRs in logic circuits.
*Application of transistors as switches.
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.
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.
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Electronics Field is very vast and for those who want to enter this segment in a systematic step by step method, the CHIP TALK offers the best platform where it provides basics of all the necessary concepts required to build projects and moreover it comes with a 40 tested projects circuits to boost your confidence in building and enjoying the projects.
CHIP-TALK Hobby Projects package includes components and breadboard for prototyping 40 fully tested projects. The book contains the fundamentals of electronics and 40 tested circuits and their descriptions.
Things which you can learn:
*Applications of different ICs like CD4011, CD4001, NE555, op amp etc.
*Application LED, IR LED, Variable resistor and capacitor, inductor.
*Application of L14F1.
*Application of ultrasonic transmitter and receiver.
*Use of breadboard.
*Application of transistor as amplifier and switch.
*Use of different switches like DPDT, SPDT, SPST.
*Use of relay.
An Awesome platform for those who are looking to build and learn electronics project with easy access to all the circuits and necessary informations supporting the project.
CHIP-TALK Hobby Projects package includes components and breadboard for prototyping 40 fully tested projects. The book contains the fundamentals of electronics and 40 tested circuits and their descriptions. Below is the list of projects:
1.Circuit Symbols & conventions
2.Basic Tools and Test Equipment
Trimming tool set.
4.Safety precaution for preventing electric shock
6.Fixed and Variable Resistors
Resistor Colour code and conventions
The E12 Range
The E24 Range
Simplifying The Color Code
7.Capacitors and capacitive reactance.
Colour coding and marking schemes for fixed capacitors
IEC letter and digit code for r & c values
Conversion table for capacitance values
8.Inductors (coils) and inductive reactance
Printed Circuit Board
10.Illustrations of some commonly used components
Light Emitting Diode (LED)
7-Segment LED display
12. Versatile TTL/CMOS Logic and Clock Probe
12.UM66TXXX Melody generator-based projects
13.Project 1. A simple melody player
14.Project 2. Melody player using speaker
Modifications UM66TXXS (single shot)
15.Project 3. Musical call bell
16.Project 4. Musical hold-on for Telephone
17.Project 5. Timer with Musical Alarm
18.Project 6.Intercom with Musical Ringtone
19.Project 7. Soft Musical Telephone Ringer
20.Project 8. Touch-sensitive Musical Bell with delay
21.Project 9. Musical Continuity Tester
22. TTL and CMOS logic based circuits
Comparison. (CMOS VS TTL)
23. CD4011 quad 2-input NAND gate to realize:
Inverter. Or Not gate
24. NAND gate(s) based circuits
Project 10. A set-reset (Bi-stable) flip flop
Project 11. Touch Sensitive Alarm
Project 12. On/off Ringer
Project 13. Toilet Busy Indicator
Project 14. Electronic Direction Pointer
Project 15. Simple Soil Moisture level Controller
Project 16. Touch Sensitive Single-chip Flasher-cum-beeper
Project 17. Automatic Pump Controller
Project 18. Generating Three Tones Using a Single digital IC
25. Timers and Counters
555 Timer and 556 dual Timer
Monostable mode (555 timer)
Astable mode (555 timer)
CD4026B and CD4033B Counters
26. Timer and counter based circuits
Project 19. Divide-by-N counter using CD4033
Project 19A. Divide-by-2 through 6 and 8 (using CD4033)
Project 19B. Divide-by-7 counter (using CD4033)
Project 19C. Divide-by-9 counter (using CD4033)
Project 20. Divide-By-N Counter Realization
Using 555, CD4033 And CD4017
Project 21. Telephone Call Counter
Project 22. Mains Interruption Counter with Indicator
Project 23. Timer For Students
Project 24. DICE with 7-segment display
Project 25. Simple smoke Alarm
Project 26. Concealed AC mains line detector.
Project 27. Speed Control Of Dc Motor Using Pulse-Width Modulation.
Project 28. IR to RF Converter.
Project 29. Contactless Telephone Ringer.
Project 30. Preamplifier (signal booster) for FM Band.
Project 31. Condenser mike Amplifier.
Project 32. Cordless F. M Mike.
Project 33. Laser Controlled On/Off Switch
Project 34. Phone broadcaster
Project 35. Anti-theft Alarm.
Project 36. Touch Dimmer.
Project 37. Doorbell using UM3561
Project 38. Poor man’s Miniature hearing Aid.
Project 39. Line-powered two-tone ringer.
Project 40. Ding-Dong Bell.
Project 41. Rechargeable White LED Torch
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.
Things which you can learn:
*Application of C2570 transistor.
*Working of trimmers.
*Maximum Power Transmission
*RF pre amplifier setup.
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.
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.
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.
Things which you can learn:
*Application of NE 555 timer.
*Application of TRIAC BT136.
*Application of Zener diode as a voltage regulator.
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.
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.