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Old 09-01-2010, 02:39 PM   #21
ChowderMonkey
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Nov 2008
Posts: 5

This link might be an option.

http://benkrasnow.blogspot.com/2010/...ontrol-by.html



 
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Old 09-01-2010, 04:13 PM   #22
kwantam
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Aug 2010
Austin, TX
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Of the solutions suggested, performance-wise the best is the triac dimmer ChowderMonkey linked, but in this application (very long thermal time constants), you can easily afford to PWM with a sub-Hz switching rate and notice no difference. In the end, I'd do whatever is easiest and cheapest.



 
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Old 09-10-2010, 02:54 AM   #23
Bixter1
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Aug 2010
Philadelphia, PA, PA
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Im going to being using a microcontroller and I figure that I would just cycle the heating element on and off as needed (depending on the temperature) and I plan to have my fluids always moving. Would I need to bother with a PWM setup? I guess technically I am doing PWM if I am cycling the SSR on and off every few seconds.... Do you all think its better to do a PWM/similar circuit that would regulate the heating element output or just pump it on and off with a IO pin?

 
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Old 09-10-2010, 03:28 AM   #24
chunk1227
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Aug 2010
Texas
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Quote:
Originally Posted by Bixter1 View Post
Im going to being using a microcontroller and I figure that I would just cycle the heating element on and off as needed (depending on the temperature) and I plan to have my fluids always moving. Would I need to bother with a PWM setup? I guess technically I am doing PWM if I am cycling the SSR on and off every few seconds.... Do you all think its better to do a PWM/similar circuit that would regulate the heating element output or just pump it on and off with a IO pin?

kwantam says it best above.

From all my research it is the cheapest and easiest to just turn the element on and off at full power in matters of seconds. ie, if you want 50% power, turn element on for 2 second and off for 2 second or something similar. I wouldn't go much below a 1 second on/off cycle though.

Triac dimmers will work, so would the analog SSR posted earlier. But in the end, those things just add unneed complexity and costs.

 
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Old 09-10-2010, 05:44 AM   #25
BayerischBier
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Dec 2009
Boise, Idaho
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Well the question is whether do you just want to control ONE pwm circuit or more fun as well?
YOU WANT MORE!!

The arduino gives you the option to do more than a regular control circuit or a PID.

Let's warm-up with the legendary reference:
http://home.highertech.net/~cdp/boilnew/boilnew.htm
classic self-built control pwm based....

This is the current follow-up:
http://www.homebrewtalk.com/f51/pwm-...ontrol-159193/

or you get this one:
http://www.bakatronics.com/shop/item.aspx?itemid=383
dirt cheap for a pwm kit (cheaper then the arduino or clone), add an SSR to it and have fun uhmm brew beer.

Right now I am brewing electric on 2 x 1500W elements on two separate 20A breakers (apartment brewing) with an modified RPC (roomie pulse control ) which switches on/off in a 2sec cycle - the catch RPC gets tired or looses pace due to beer sampling.

I am lurking at an arduino with 3 SSRs (two for the kettle, one for the HLT) , run HLT and one brew element on the same circuit, and let the software swap the power between the elements (hlt/1 brew) on the circuit.


The beauty of this? Change the sketch (program) on the arduino and you switch from brewhouse setup to lagering/fermentation chamber!! just plug the controls into your Son of Fermentation version with a mini-fridge. Then you can cycle the fridge trough one SSR and still have two left for the fans (if they are not 12V). And your lager beer will still stay cool if you brew for a few hours.

 
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Old 02-10-2012, 08:41 PM   #26
MrWhat
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Feb 2012
ALBUQUERQUE, NEW MEXICO
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For a fairly slow heating process, where temperatures change over minutes, not milliseconds, using a relay, I'd program my own PWM.
Turn the relay totally on and totally off over a longer pulse interval, like 10 seconds to 1 minute. As noted by others, relays are not intended to switch at 500Hz. especially not with AC input.



 
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