EMI interference with PID controllers

[bigdan]

AJ is right. If it's an AC coil the diode will not work and if you use the diode you won't be able to use the coil you have. Depending on the valve you have you might be able to change the coil, but a lot of HVAC equipment has the coil built into the valve and safeties.

[ggltd]

Thanks for all the great info. When it comes to this type of electronics I am way behind the curve. I went with the salvaged gas valves to save some cash but maybe was a bad idea from the start. Anyhow, I think I will first try the ferrites as this would be the easiest and then go from there, as the coil on the valve is AC and I can’t use the diode.

[bigdan]

What kind of valve is it? You could try the magnets. If that didn't work you could try and run a very small ice cube relay that would then run the valve to see if that would help the controller. Other than that I'm betting you will have to look at another valve or a simpler control like one of the Ranco's no PID. Let us know what you try and how it works. One other thing to try... see if your control is set on PID or on/off and try on/off and see if that works. PID would be more important for electric heat than gas.

[ajdelange]

Thanks for all the great info. When it comes to this type of electronics I am way behind the curve. I went with the salvaged gas valves to save some cash but maybe was a bad idea from the start. Anyhow, I think I will first try the ferrites as this would be the easiest and then go from there, as the coil on the valve is AC and I can’t use the diode.

But yoy can use the diode if you are willing to invest all of $2.00 or so on a bridge (Radio Shack has them) and it will probably solve the problem.

[bigdan]

AJ wouldn't he need a dc coil on the valve, if he uses the bridge?

[ajdelange]

Probably not though the coil might run a little hotter because of no AC impedance (inductive). Were this this case a current limiting resistor would solve the problem though as there will be a small voltage drop across the bridge I'm guessing this wouldn't be necessary.

Going to DC isn't, of course, the only way to solve this problem. I've suggested power entry modules (EMI filters) in earlier posts and others have mentioned ferrites which might also work.

[Cliff]

Din't I warn you about detonating nukes near your brewery?

[ggltd]

Hi everyone, and thanks for all the good info. At the end of the day Auberin and I worked this out. First the controllers can only be powered by 110 V AC, not the 24 V that I am using for the rest of the gas valve circuits. Even though the manual said I could. And second the main problem was the one temp probe actually had an intermittent short and Auberin finally agreed to give me a new one. However I did place ring magnets at strategic places which I also believed helped this problem. Everything is working fine now and I hit my mash temps within 2 degrees. So I guess Occam's razor applies here.