Serial data noise when attaching AC load to triac

Other Hardware General Electronics
1

Hey all,

I'm a real newb here, so go easy on me. I'm playing around with an LCD touchscreen (the ezLCD), and it works great. I've got a circuit attached that sends timed pulses to a triac for AC load control. My serial communication to the LCD works 100% when the AC load isn't attached, but as soon as I plug it in I get enough noise on the serial data line that about 20% of the data is misread.

It's all hooked up on a breadboard, but it's fairly neat and I do expect some noise given the setup. What approach might I take to filter out this noise from the serial input? I've been googling decoupling capacitors and RC filters, I don't really know much about either and am wondering if that is the correct route to take. I'm not sure if I should be applying the filtering to the serial line, the VCC of the LCD or the VCC of the arduino. I'm a little confused :~

2

You have the AC load connected to the breadboard?

3

Post the schematic of what you have. You can't use decoupling on an AC circuit.

4

How long is the wire(s) going from the processor to the LCD?

5

The LCD wire is about 3 inches. Yes, AC is connected on the breadboard and optically separated from the DC circuit with 6 inches of separation for safety and noise. I'm only running very low current for obvious reasons as this is a test setup.

I'll draw up a schematic shortly - I'm aware you can't decouple AC - I was referring to the DC side of the circuit which is clearly picking up noise from the AC side, or the frequencies generated by the zero cross detector.