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Author Topic: Arduino lcd goes blank after a while when switching 220 ac  (Read 382 times)
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Hi All

I am new here and would like some help please.

I am switching 2 power heads (220ac) with a Uno R3 I have a 2n35 switching a n Channel mosfet witch interns switches a 12V relay. The cuircut works fine but after about 20 min my lcd goes blank but the controller still runs fine. The only way to get the lcd up is to rest the unit. If I remove the relay connections the uno runs fine as i have it monitoring the room temp. Is there any ideas or an alternitive option to my problem?

Do I need to change the n Channel for a tric ?



Regards
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Sounds like you need more bypass capacitors and isolation. Does it happen without the 220 V AC on the relay? i.e., just when the relay switches? Do you have a flyback diode on the relay?

Do you really need *two* drivers for the relay coil? A logic level MOSFET should work fine.
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I have a fly back diode on the relay and it does not happen when the 220 ac is not connected. I just wanted to make sure that i have good isolation from the controller as the plan is to use pwm in future with a diac or tric to not completely turn off the power heads but to ramp them up and down from -+30% to 100%.  Currently i am just turning them on and off in intervals whicths works fine for 20 to 30 min.

Thanks for the reply i will look into some more options maybe i can find 12 v Units which will make a big difference 
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Sounds like arcing from the relay switching is causing interference. You might put a snubber across the 220 V terminals, add some shielding or more bypass capacitors to the arduino board/LCD board.

Note that the Triac will not cause arcing, so the issue might be solved going to a solid state switch.
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