yjfun

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I'm running the bakatronics kit with the 2.2 cap and the only thing I noticed is my element range seems to be from about 10%on to 90% on. I can't shut it all the way down or get full power from it.

GregKelley

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Hmm. I'm wondering if I should then add a simple switch to my PWM layout so that I can bypass the circuit and just feed the 5v and ground directly to the SSR. Throw the switch one way and the PWM is bypassed. Throw it another and the PWM is in use.

pvtschultz

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If you have enough room, I would install a 240 VAC 2-pole 30A contactor to disconnect the element. The contactor costs ~$5 and then you can use a simple 10 Amp or so SPST switch to disconnect it. You are right though, without a physical disconnect, there will always be voltage at the element since the SSR is a current limiting device.

Contactor

LEDs are very simple little gizmos that just need to have the voltage going to them limited. Your application sounds quite straight forward. I would place one parallel to the supply side of your PWM circuit and one parallel to the V-out going to the SSR. The link below will help you select a resistor to place in series with the LED to keep it from burning out from over-voltage. 20 mA is a typical forward current value for LEDs so just plug in your supply voltage and then pick a color and they calculator will spit out the resistor that needs to be put in series with the LED.

http://www.hobby-hour.com/electronics/ledcalc.php

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Brewing: Kona Fire Rock Pale Ale Clone
Drinking: KingBrian's Caramel American Amber Ale
On Deck: Classic American Pilsner, Raspberry Brown Ale, Dunkel, Schwartzbier
2013 Gallons Brewed: 30
Gallons Brewed '11-'12: 170

http://www.homebrewtalk.com/f170/pvtschultzs-ebiab-build-finally-298407/

clearwaterbrewer

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I would use a potentiometer with an inclusive on-off switch (separate internal switch and external contacts) to turn the 12V to the PWM circuit on and off, I would use one LED to show this on and off, and the other LED tied to the output of your PWM circuit that drives the SSR.

pvtschultz

Recipes 

I generally leave my potentiometer set to a experimentally determined 15% boil off rate, but a simple mark to remember the set point would be easy enough. I use a keyed switch (mostly for looks) to turn the main power on and off which feeds to my PID and PWM.

__________________
Brewing: Kona Fire Rock Pale Ale Clone
Drinking: KingBrian's Caramel American Amber Ale
On Deck: Classic American Pilsner, Raspberry Brown Ale, Dunkel, Schwartzbier
2013 Gallons Brewed: 30
Gallons Brewed '11-'12: 170

http://www.homebrewtalk.com/f170/pvtschultzs-ebiab-build-finally-298407/

Walker

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Back in post #173 I had a pic of a partially assembled breadboard with a PWM circuit on it. More than one person has copied that circuit to the letter and had issues with it working, and I realized that there is a critical error in the picture. I added a large red comment to that post to clear things up, because it will absolutely screw up the circiut behavior.

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GregKelley

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Thanks for the update, Walker. So back to the drawing you have under your red comment. You are talking about the 33μF cap, right? The negative side should connect to the negative side of the power source and the other side should be connected to pin 6 on the 555 timer? I guess I have mine turned around as well. I have a blue cap with a black stripe. I'm assuming that stripe is the negative side? The circuit seemed to work a little weird in testing but I chalked that up to the LED on the SSR not properly showing how the circuit was working.

Durhamite

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Thanks again for the help Walker. Once I flipped that capacitor around it worked perfectly!


For anyone else that may be experiencing issues, mine was only turning the SSR on when I turned the potentiometer up to about 90%. Anything less than that was "off".

Walker

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Yup. The grey stripe should be to the negative voltage node of the circuit and the non-Grey side connected to the chip. You have it backwards.

Flip it around and it should work perfectly.

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Ground Fault Brewing Co.

GregKelley

Recipes 

The circuit does appear to work better from observing the LED on the SSR. But now I've observed something else odd. It appears that it takes 3-5 minutes for the circuit to get going. When I enable power to it, it does not turn on the SSR at all. A few minutes later and it works fine. If I kill the power and then re-apply the power, the circuit works fine. Do I have a bad capacitor that is taking too long to charge up?