Arduino Rebooting


I'am controlling TRIAC BTA40 with arduino, I have zero-cross detector and circuit to fire the TRIAC gate at the right angle. The software works well, but here is the deal. Sometimes when I plug the 5500W resistance in the 220V wall plug, my arduino reboot and freezes, the LCD stops working.

Anyone have and idea whats is going on? is there good filter I can make to prevent Arduino rebooting?


Looks like "digital out" and "digital in" are reverse labelled in your diagram. My guess is RFI or voltage transients falsely turning on the thyristor. I agree that some sort of filter (snubber circuit) would be needed.

Hello dlloyd,

Thanks for your answer, and yes "digital out" and "digital in" are reverse labelled, I will fix it.

I have tried the snubber circuit even though my load is purely resistive, tried 44R and 0,33uF in parallel with the load, but no luck.

Are you serious about the 5.5kW load? That's 25 amps. Is your electrical system designed for that?

I wonder if it's causing the Arduino power supply to lose voltage and make the Arduino reset.


Well, I guess I just fixed.

Yes, the load uses up to 25A, the system is designed for that.

The Arduino is powered with 12V supply, and regulated with LM05, and I’am using some 1000uF capacitor to filter and also decompiling capacitors 100nF.

I just added the snubber circuit in parallel with TRIAC Gate and A2, and is working fine, I can turn the load ON and OFF, and also power water pump in the same AC power line and no reboots.

Here is the updated circuit diagram:

vinicaog: and also decompiling capacitors

I suspect lots of folk here would like some of these. Where did you get them? :)