Go Down

Topic: Serial data noise when attaching AC load to triac (Read 1 time) previous topic - next topic

replaysMike

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  :~

Coding Badly


You have the AC load connected to the breadboard?

Grumpy_Mike

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

nickgammon

How long is the wire(s) going from the processor to the LCD?
Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics

replaysMike

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.

Go Up