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Microcontroller Based Water Level Controller cum Motor Protector

by KNS Pvt Ltd
Save Rs. 201.00
Rs. 1,700.00
Rs. 1,499.00

Summary

The Micro-controller based Water Level Indicator cum Motor Protector circuit uses the micro-controller AT89C51 as the main controller. It can be used to switch ON and OFF the motor depending upon the level of the water in the tank. The status is displayed on an LCD module. The circuit also protects the motor from high voltages, fluctuations of mains supply and dry running.

Product Description

The Microcontroller based Water Level Controller cum Motor Protector controls ‘on’ and ‘off’ conditions of the motor depending upon the level of water in the over head tank (OHT), the status of which is displayed on an LCD module. The circuit also protects the motor from high voltages, low voltages, fluctuations of mains power and dry running.


Working

The circuit of the Microcontroller based Water Level Controller cum Motor Protector comprises of the operational amplifier LM324, microcontroller AT89C51, optocoupler PC817, regulator 7805 and an LCD module. Port pins P2.0 through P2.2 of the AT89C51 (IC2) are used to sense the water level, while pins P2.3 and P2.4 are used to sense the under-voltage and over-voltage, respectively. Pin P3.4 is used to control relay RL1 with the help of optocoupler IC3 and transistor T5 in the case of under-voltage, over-voltage, and different water-level conditions. The LM324 (IC1) is a quad operational amplifier (op-amp). Two of its op-amps are used as comparators to detect under- and over-voltage. In normal condition, output pin 7 of IC1 is low, making pin P2.3 of IC2 high. When the voltage at pin 6 of N1 goes below the set reference voltage at pin 5 (say, 170 volts), output pin 7 of N1 goes high. This high output makes pin P2.3 of IC2 low, which is sensed by the microcontroller and the LCD module shows ‘low voltage.’

In normal condition, pin 1 of N2 is high. When the voltage at pin 2 of N2 goes above the set voltage at pin 3, output pin 1 of N2 goes low. This low signal is sensed by the microcontroller and the LCD module shows ‘high voltage.’
Presets VR1 and VR2 are used for calibrating the circuit for under- and over-voltage, respectively. When water in the tank rises to come in contact with the sensor, the base of transistor BC548 goes high. This high signal drives transistor BC548 into saturation and its collector goes low. The low signal is sensed by port pins of microcontroller IC2 to detect empty tank, dry sump, and full tank, respectively.

When water in the tank is below sensor A, the motor will switch on to fill water in the tank. The LCD module will show ‘motor on.’ The controller is programmed for a 10-minute time interval to check the dry-run condition of the motor. If water reaches sensor B within 10 minutes, the microcontroller comes out of the dry-run condition and allows the motor to keep pushing water in the tank. The motor will remain ‘on’ until water reaches sensor C. Then it will stop automatically and the microcontroller will go into the standby mode. The LCD module will show ‘tank full’ followed by ‘standby mode’ after a few seconds. The ‘standby mode’ message is displayed until the water in the tank goes below sensor A.

In case water does not reach sensor B within 10 minutes, the microcontroller will go into the dry-running mode and stop the motor for 5 minutes, allowing it to cool down. The LCD module will show ‘dry-sump1.’ After five minutes, the microcontroller will again switch on the motor for 10 minutes and check the status at sensor B. If water is still below sensor B, it will go into the dry-running mode and the LCD module will show ‘dry-sump2.’ The same procedure will repeat, and if the dry-run condition still persists, the display will show ‘dry-sump3’ and the microcontroller will not start the motor automatically. Now you have to check the line for water and manually reset the microcontroller to start operation. In the whole procedure, the microcontroller checks for high and low voltages.

For example, when the voltage is high, it will scan for about two seconds to check whether it is a fluctuation. If the voltage remains high after two seconds, the microcontroller will halt running of the motor. Now it will wait for the voltage to settle down. After the voltage becomes normal, it will still check for 90 seconds whether the voltage is normal or not. After normal condition, it will go in the standby mode and start the aforementioned procedure.
 

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Stepper Motor Control Using ATC Microcontroller

Summary

Stepper motors are used for precision position control in many applications like floppy drives, printers, process control instruments, robotics and machine tool control. The Stepper Motor Controller using the 89C51 micro-controller can accurately control the rotation direction (clockwise or anti-clockwise), speed and number of revolutions with help of six tactile switches. This module is simple and easy to construct and can be used in many application e.g. Machine control, Robotics for controlling the axial rotation in XY plane. A similar circuit can be added to control the rotation of the motor in either XZ or YZ plane.

Learning

Things which you will Learn:

*Application of the AT89C51 microcontroller for stepper motor control and interfacing.
*Implementation of the bridge rectifier.
*Programming of the AT89C51 microcontroller in Assembly language.
*Concepts of Stepper motor angle.

Product Description

Robots are the future of the World and the main element in them is the stepper motors for joins and actuatiors. So we bring you a simple circuit for controlling the Stepper motor using the IC AT89C51.

Working:

At the heart of the Stepper Motor Controller is an AT89C51 microcontroller. From traffic control equipment to input devices, computer networking products, and stepper motor controllers, 89C51 microcontrollers deliver a high performance with a choice of configurations and options matched to the specific needs of each application.

In the Stepper Motor Controller circuit, the control switches for the motor are connected to Reset and Port P0.7 pins of the microcontroller while the stepper motor is connected to port pins P2.4 through P2.7 of the microcontroller (IC2) through the motor-driver circuit consisting of four Darlington pairs comprising transistors BC548 and SL100 (T1-T2, T3-T4, T5-T6, and T7-T8). 

When transistors conduct, 5V (Vcc) is applied to the coils of the motor and the currents flowing through them create magnetic fields and the motor starts rotating. The magnetic field energy thus created is stored in the coils.

When transistors stop conducting, the power to the coils is cut off, the magnetic field collapses and a reverse voltage (called inductive kick back or back emf) is generated in the coils. The back emf can be more than 100 volts. The diodes connected across the coils absorb the reverse voltage spike.

Timing:

The crystal frequency used in this circuit is 11.059MHz. The speed of the stepper motor is proportional to the frequency of the input pulses or it is inversely proportional to the time delay between pulses, which can be achieved through software by making use of instruction execution time.

When power is applied, the reset input must first go high and then low. A resistor-capacitor combination (R1-C3) is used to achieve this until the capacitor begins to charge. At a threshold of about 2.5V, the reset input reaches a low level and the microcontroller begins to function normally. Reset switch (S2) allows you to reset the program without having to interrupt the power.

Driver Circuit Design: Ports P0 through P3 of the microcontroller are not capable of driving loads that require tens of milliamperes (mA). The microcontroller outputs a current of 1.7 mA. To drive the coil of a stepper motor requiring a torque of 7 kg-cm, 12V DC and 2 amp/phase, a driver circuit using transistors SL100 and 2N3055 are used to amplify the current to 2.72 amp. Since the stepper motor has four coils, we need to use four Darlington pairs.

Programming:

The program for the Stepper Motor Controller is written in Assembly language and compiled using the ASM51 cross-assembler. The AT89C51 is programmed using Atmel Flash programmer. One step rotation of he stepper motor used in this project equals 1.8 degrees. When the motor is programmed for 200 steps, the motor makes one complete revolution i.e. 360 degrees.

Click To View Circuit Diagram

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