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Control Triac using the microcontroller without MOC

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Newbie level 3
Sep 28, 2010
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Hi all.

I want to control triac directly by using a microcontroller without MOC. Plz. everyone can show me the schematic or the guidance.

Hope someone can help.

If you dont use an opto, you loose isolation between your micro circuit and the mains. Is that acceptable? What kind of power supply do you have driving the microcontroller circuit?

you better use any isolator if you dont want moc, you can use 4n25 or 35 etc. but for that, you have to use another separate power supply. if you still need that, tell me i will send u circuit diagram

Thank @Noman Yousaf @ard
I don't need to isolate because I want smaller circuits. You can give me a diagram.


the use of isolation is not to make the devices bigger, it is the demand for safety.
You need to comply with the safety regulations of your country.


The datasheet of the triac will tell you at which pin of the triac is the reference pin for the gate voltage.
And it will tell you what voltage and what current is needed to trigger the gate.
With this informatiion and the specification of your microcontroller you will find out if you need a driver chip or a simple port pin is enough.

We can´t answer the questions, because we don´t know the triac type nor the microcontroller type and VCC voltage.


Some home appliances have a microcontroller directly tied to mains power and can use direct triac control. The disadavantage is that the microcontroller circuits and all switches, displays, sensors etc. must be protected against accidental contact like high voltage circuits.

Testing and debugging a circuit with direct mains connection needs special precautions, e.g. safety transformers, and isn't recommended for hobby projects.

The requirements for direct triac control have been discussed in a "similar thread" linked on the bottom of page

Because DC triggered triacs are best operated with negative gate voltage, triac MT1 is often tied to VCC terminal in this kind of designs.

Thank all of friends
I use a atmega8 and a BTA12. If the circuit run, I will post to everyone.

In this situation to get more safety, but not enough, from mains neutral to be connected to GND. Use transil (~400V/100A) to maximim eliminate voltage spikes and resistor to gate of BTA to be >=0,5W , because burn to me several times.

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