Control SCR w/ Microprocessor & Opto Coupler

[Waquas Mehmood]

How can we control an SCR through a microprocessor with an opto coupler used as an 'isolating and amplification' device between the microprocessor and the SCR.

 

[Averagesupernova]

Sounds like a homework question to me...

 

[berkeman]

I agree. It'll probably get moved to the homework forum. Waquas, what do you know so far about how SCRs are driven and how they are used? What is unique about the SCR structure? How do you turn them on and off?

 

[Waquas Mehmood]

Reply

I have read much about SCRs, their turn on and turn off methods and characteristics. Also I know about triggering an scr (Firing circuits), etc. This question was posed by my teacher. He asked whether we can drive an scr through a microprocessor, i.e., control it by a microprocessor. The reason why this question was asked is actually because currents driven through a microprocessor are of the order of milliamperes and those through an scr are of the order of tens of amperes.

 

[berkeman]

What is the trigger current and voltage typically? How do you shut off an SCR?

As for using a uC to control the gate, think about the timing accuracy required, and how you would accomplish that timing using a uC. Are you talking about controlling a 50-60Hz line frequency device? Or something more like a solenoid-based machine?

 

[triden]

Since the microcontroller cannot handle the current that the SCR needs, you will need some sort of current amplification stage after the MCU. This could either be a transistor (easiest) or some sort of buffered driver. You can drive almost anything you want with an MCU aslong as you have the right output stage after it.