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Project Platform : PWM EMBEDDED C 89X5X MICROCONTROLLER
Languages Used : EMBEDDED C
Project Cost : 15000
The basic aim of this project is to control the speed of the DC and AC motor using Pulse Width Modulation in master slave manner where master is the one who has the 4x4 keypad who first selects which slave to run either DC motor connected slave or Ac motor Connected slave., and after selection of slav provide the speed value at which the slave is to be running. In microcontrollers, we can change the speed by using delay. The delay can be provided by two procedures, first one is by using “for loop” and the second one is by using “Timers”. The former method is not efficient so we used the latter technique.
The minimum and maximum ranges of timers are fixed depending upon crystal oscillators. So, “for loop” was used for number of counts. Since 11.0592 MHz Crystal Oscillator is being used, so in timer 0, mode 1 the minimum time delay is 1.085u seconds and the maximum time delay is 71m seconds (approx.). Due to this limit of maximum time delay, “for loops” was used for number of counts.
Without User-Interface, the device is non-usable so, 4x4 keypad interface was attached. By using this interface, user can easily change the speed of the motor.
Pulse Width Modulation (PWM)
Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a commonly used technique for controlling power to inertial electrical devices, made practical by modern electronic power switches.
The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast pace. The longer the switch is on, compared to the off periods, the higher is the power supplied to the load.
The PWM switching frequency has to be much faster than what would affect the load, which is the device that uses the power. Typically, switching has to be done several times a minute in an electric stove, few kilohertz (kHz) to tens of kHz for a motor drive and well into the tens or hundreds of kHz in audio amplifiers and computer power supplies.
The term duty cycle describes the proportion of 'on' time to the regular interval or 'period' of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on.
Hardware Required :
1 x 7805 Voltage Regulator
2 x 100nf capacitors
1 x 1000uf ; 35v capacitor
1 x 100ῼ resistor
Green Dull LED (For Power indication)
1 x 10uf ; 16v capacitor
1 x 8.2kῼ resistor
1 x 11.0592MHz Crystal Oscillator
2 x 33pf capacitors
3 x AT89C52 Microcontroller
3 x 40 pin Base of AT89C52
1 x 6 Strip Connectors
1 x (4x4) Keypad
1 x DC Motor and AC Motor
1 x TIP122 Darlington Transistor
1 x 270ῼ resistor
1) Embeded C using keil c51