Hi guys, I have another temperature control project which is exhibiting an offset issue. I'm powering 2 5v regulators with a 12v switching power supply. 1 regulator powers an LCD screen and the arduino uno, the other powers the 2x5v relay board for switching AC.
The sensor input op amps and conditioning runs off of the 12v supply so I can use the full 5v range with a low noise floor going into the Uno. Everything has a common ground and there are a few decoupling caps on the regulators and in the arduino. My 12v bench supply can deliver 22A, so plenty of headroom, there.
The Problem: When the relays click on the input voltage to the Uno analog pin (from the sensor circuitry) drops slightly, giving a false reading. The offset changes depending how close I place the relay ground and power to the 12v supply. Is there an easy way to better-isolate the relay power from the rest of the system?
My other thought was to use a 24v supply and use a regulator to isolate the sensor circuitry at 12v and see if the relays effect the 12v regulated side. I worry that a bad ground would introduce a ground offset and effect the Uno reference. In the end I want a single power supply for the entire system so it is compact. Thoughts? Thanks for reading :)