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Trouble with PID

http://www.thebrewingnetwork.com/forum/viewtopic.php?f=4&t=16276

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Trouble with PID

Posted: Wed Aug 12, 2009 3:48 pm
by Jim Dawg
im currently working on a Herms system. i've been testing my PID. i set it up to turn on/off a lamp and as far as i know it is set up correctly. my problem is i can only get the lamp to flicker every 1-2sec intervals. the PID im using is TC-408A and i have a 25A SSR. if anyone has used my same PID or knows what the matter could be i would greatly appreciate any help you can give.

-Jim

Re: Trouble with PID

Posted: Thu Aug 13, 2009 8:24 am
by GrahamW
Jim Dawg wrote:im currently working on a Herms system. i've been testing my PID. i set it up to turn on/off a lamp and as far as i know it is set up correctly. my problem is i can only get the lamp to flicker every 1-2sec intervals. the PID im using is TC-408A and i have a 25A SSR. if anyone has used my same PID or knows what the matter could be i would greatly appreciate any help you can give.

-Jim

That is how it is supposed to work, more or less. With the set-point set far below the probe temperature the lamp should be fully on. With the set-point set above probe temperature, the lamp should be off. With the set point close to (just below) probe temperature it should cycle in two-second bursts. The length of time the lamp is on in that two seconds is proportional to how far below set point the temperature actually is.

Suspend the lowest wattage lamp you can find, the probe, and a thermometer in an enclosed space, like a wooden or cardboard box, and adjust set point to, say, mash temperature. Eventually the temperature should stabilise at mash temperature with the lamp giving a short burst every two seconds. Careful you don't set fire to your box if using cardboard.

There is a fair amount of setting up required, to set probe type and bust length, but it seems from what you say that you are already there.

Re: Trouble with PID

Posted: Thu Aug 13, 2009 8:39 am
by BrewTa2
What input does the relay require? If 8v DC is not in the range, that's your problem.

Re: Trouble with PID

Posted: Thu Aug 13, 2009 10:58 am
by Jim Dawg
I figured it out thanks guys. my problem was in my tests i had the difference in temps really close. i had that lamp glowing like it's never glowed before :pop

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