adjustable firing angle control of thyristor using arduino



Adjustable firing angle control of thyristor using arduino, Hi everyone this project is about adjustable firing angle control of triac or thyristor using Arduino Uno. In this project , we have designed a circuit diagram to control the phase angle of thyristor over a complete sine wave or complete ac cycle for both negative and positive half cycle. This project has many applications like ac power control with thyristor and speed control of single phase induction motor.I have already posted a article on thyristor firing angle control circuit using analog electronics components. But in this project, I have created a adjustable firing angle with digital electronics components like Arduino.  So now lets start with basic introduction of all the components which are used in this adjustable phase angle control of thyristor using arduino.



Components  used in adjustable firing angle control of thyristor

Followings are the main components used in this project.

  • Zero crossing detection circuit
  • Bride rectifier : It is used to convert negative half cycle to positive half cycle.
  • resistors
  • 4N25 optocoupler
  • diodes
  • Thyristor
  • Arduino Uno R3
  • variable resistor : It is used to control firing angle time.

Zero crossing detection circuit

Circuit diagram of zero crossing detection circuit is shown below.  Zero crossing circuit is used to detect zero crossing of ac cycle after every half cycle. Because we want to control phase angle for both positive and negative half cycles. The length of triggering pulse should be same for both positive and negative half cycle. So zero crossing detector circuit is must to design adjustable firing angle control of thyristor using arduino. 4N25 optocoupler is used for isolation between high side voltage and low side voltage and it also helps to detect zero crossing. The output of zero crossing D2 will be fed to Arduino.

zero crossing detctor for adjustable firing angle control



Circuit diagram of adjustable firing angle control of thyristor using arduino

  • Complete circuit diagram of adjustable firing angle control of thyristor using arduino  is shown below.
  • In this circuit diagram variable resistor is connected with analog channel zero of Arduino.
  • Variable resistor is used to adjust the firing angle of thyristor or triac.
  • MOC3021  is a optically isolated thyristor or triac driver.
  • Input to MOC3021 is firing pulse for thyristor which is used to turn on and turn off thyristor.
  • At the output 220V AC lamp is used in series of ac power supply.
  • When thyristor is off, lamp will be off and when thryistor is on, lamp will also be on.
  • So the power across the lamp depends on the on time of thyristor which is ultimately depends on firing angle of thyristor

Adjustable firing angle control circuit for thyristor using Arduino

  • So output power across the lamp depends on the firing angle to the triac or thyristor.
  • Greater the firing angle, less will the voltage or power across the lamp as you can see in this picture. Adjustable firing angle control circuit
  • So firing angle is basically a reference at which thyristor will turn on. If thyristor turns on late, less voltage will appear across the device and hence less power.
  • For more information check this video

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