PID overkill?

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Garyr2973

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Is using a PID to regulate temperature on a keezer overkill? I don't want to burn up the compressor but I also want it to stay at the temperature I set (or very close to it)?
 
Not as much overkill as the wrong tool for the job. A typical PID output is designed to go to an SSR and/or contactor to control the electric device, whether a heating element in an electric kettle or a compressor for a keezer. They also cost $40-50, not including SSR, heat sink, contactor, etc, which can total over $100, and require some extra time/labor. You can get an "aquarium controller" like an STC-1000 for $20-30 that was designed to maintain even temps with 2 110V loads (heating and cooling), and is very simple to wire up (tons of info on other threads here).

Of course, some aren't as blingy as a PID.
 
The STC-1000 is the go to cheap controller it seems (I have one :D). I have not seen many prewired ones so you will probably have to do a bit of DIY and a few more parts like a box, power sockets, etc. (you would need all this for the PID anyway). Love and Johnson are the other 2 controllers that come to mind for this, basically the same except the have been round longer aand some come prewired (check out northern brewer I think?).
There is a Ebay controller thread on here that details the STC-1000 build pretty well.
 
PIDs are great for controlling fridge temps. You should use a relay not a SSR with a heatsink. Auberins cheapest PID will do it with the little relay. Add a thermocouple and you could probably ship for around $50.

But first read this thread. You'll be surprised how constant your temps will be. Try sticking a thermometer in a cup of water in the fridge overnight. Check the temp in the morning and then several times throughout the day. It's always held constant for me. If you're not sure why this happens, Google specific heat of water and air.
 
i use a pid on one of my keezers, but only because i already had it (got it for free during an upgrade at my work) and i had everything lying around in the garage to put it together. i programmed it to operate as a on-off control, so it operates like a ranco or johnson stand-alone controller. the only tricky part was dialing in the proper amount of hysteresis so the compressor won't short-cycle (i settled on 4 degrees, seems to work fine.)
 
I guess that is the other plus for the STC-1000, it has a build in compressor short-cycle lock out. I don't know about love/ranco/johnson though.
 
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