PWM..Show us How

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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.
 
yjfun said:
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.
Click to expand...

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.
 
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
 
Last edited by a moderator:
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.
 
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.
 
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.
 
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.
 
Thanks again for the help Walker. Once I flipped that capacitor around it worked perfectly! :mug:


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".
 
GregKelley said:
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.
Click to expand...


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.
 
Walker said:
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.
Click to expand...

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?
 
Just built mine and testing it out. Had all the components except the 500k pot. Testing it out with my power supply that will be going in my panel. It also has 5 volt out that I will be using for my amp and volt meters.
 
Here is a pic of my test.
ForumRunner_20120507_222544.jpg
 
GregKelley said:
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?
Click to expand...

Figured out the issue. The problem was a bad connection for the socket handling the 555 Timer.
 
I have ordered all the parts as Walker has suggested for my PWM build.

I really like the idea of a switched Potentiometer. Just one more element of safety that I want to add to my build.

What would be my specific wiring diagram for wiring this Potentiometer. Both input and output.

Does anyone have specific diagram? Picture would be great.

I will buy you beer.

Thank You in advance. I really appreciate it.

TD
 
I used part number POT500KBSWITCH from futurlec.com for $0.80
( I got enough pots, 555's, caps, and diodes for 10 PWM's for about $20)
http://www.futurlec.com/PotRot.shtml (last item on page)

See that the bottom has 2 contacts, not three? That is the switch.

Just run the 5V or 12V DC positive to one side, and out of the other side you connect to your positive..

here is a drawing of the ones I have been using for months:
http://c.circuitbee.com/build/r/schematic-embed.html?id=0000000245


I can email a pic from my phone if needed, PM me your email.
 
Just wanted to bump a great thread, and also share a link to the the Bakatronics PWM circuit I built into my control panel today. I wouldn't have been able to do it without the great info in this thread.

I built the circuit earlier this week and tested it using a computer case fan and 12VDC power supply and it worked great, so I wired and mounted into the control panel today. One thing I did notice is the circuit never gives you 100% Off or 100% On, it's more like 5% power and 95% percent power when the knob is turned all the way off or on. Not a big deal to me, but I just thought I'd point it out.

https://www.homebrewtalk.com/f170/m...-pid-ssr-build-281085/index5.html#post4232969

Thanks everyone!
 
bigljd said:
Just wanted to bump a great thread, and also share a link the the Bakatronics PWM circuit I built into my control panel today. I wouldn't have been able to do it without the great info in this thread.

I built the circuit earlier this week and tested it using a computer case fan and 12VDC power supply and it worked great, so I wired and mounted into the control panel today. One thing I did notice is the circuit never gives you 100% Off or 100% On, it's more like 5% power and 95% percent power when the knob is turned all the way off or on. Not a big deal to me, but I just thought I'd point it out.

https://www.homebrewtalk.com/f170/m...-pid-ssr-build-281085/index5.html#post4232969

Thanks everyone!
Click to expand...

That's great! I love my electric system. I too noticed that these PWM devices are never 100%. So I put in a switch that allows me to by pass the circuit and supply either 5v or 0v consistently to the SSR. It is a 3 way switch that will send all voltage to the SSR, send the voltage to the PWM or not send anything at all. I turn it full on until I have a rolling boil, then I switch it to run through the PWM.
 
GregKelley said:
That's great! I love my electric system. I too noticed that these PWM devices are never 100%. So I put in a switch that allows me to by pass the circuit and supply either 5v or 0v consistently to the SSR. It is a 3 way switch that will send all voltage to the SSR, send the voltage to the PWM or not send anything at all. I turn it full on until I have a rolling boil, then I switch it to run through the PWM.
Click to expand...

That's a good workaround to the problem. I'm OK with it being less than 100% power though, since I normally start heating the wort while I'm sparging when wort completely covers the element. Even running at 60-70% power during the sparge I'll usually be close to a boil by the time my sparge is complete. I may have to run it at 95% for a couple minutes to get it to a rolling boil, then I can dial it back down again. Can't wait to try this thing out!
 
I have my board all put together, but when I test it the light on the ssr stays on longer when the dial is turned down. It's as if something is reversed and when the dial is turned all the way up, the element is heating less if that makes sense. Any idea what the problem could be?
 
FrFtr28 said:
I have my board all put together, but when I test it the light on the ssr stays on longer when the dial is turned down. It's as if something is reversed and when the dial is turned all the way up, the element is heating less if that makes sense. Any idea what the problem could be?
Click to expand...

You have the left and right connections on the potentiometer switched.
 
Fired mine up for the first time this weekend!!!

It works!!!

Thanks to everyone who shared their information on this project. Doing things like this is almost as much fun as drinking the beer I make.

On to the next project...

TD
 
clearwaterbrewer said:
Here is a pic of three of them fully assembled and hot-glued..
file.php
Click to expand...

Clearwaterbrewer,

I thought that this was Walker's PWM, so I PMed him about it; now I realize that it's yours. I'm trying to decide between his, yours, or the little kit that has been recommended (with the substitute capacitor)

I hate to be asking to be spoon-fed, but I sure would like to see a diagram of your PWM. I've looked at the circuit-bee schematic. I'm a little bit familiar with circuits from my college physics classes in 1979. But . . . the way the individual components look when connected together isn't always obvious from a schematic.

I would greatly appreciate it if you would supply a drawing of how the actual components attach to the potentiometer - even if hand-drawn and not even artist quality. Did I read that you don't solder these to the pot but use hot glue to hold everything in place?

Thanks,
Keith
 
maltbarleyhops said:
this would be an "dc to ac" ssr correct?
Click to expand...

Nope. The dc side of the SSR controls the flow on the other side.

Only 1 leg of 240v or the hot side of 120v flows through the SSR on the switched side. This is where the AC is.

The control circuit is DC and controls the off/on of the Solid State Relay.

AC is being converted to DC by the wall transformer to power the PWM.
 
So i bought all the components from mouser to build walker's pwm. I have it all assembled and hooked up to my ssr. The ssr I have has an led indicator light. My question is should this light be blinking at a rate that matches how far up I turn the pot. Right now once I turn the pot on the light goes on steady.
 
szazman73 said:
So i bought all the components from mouser to build walker's pwm. I have it all assembled and hooked up to my ssr. The ssr I have has an led indicator light. My question is should this light be blinking at a rate that matches how far up I turn the pot. Right now once I turn the pot on the light goes on steady.
Click to expand...

One thing that happened to me is the wall wort I was using for power turned out to be lower voltage than the 12V it was rated for. It would only power my test light solid. Once I hooked up another wall wort that truly did put out 12V, it worked as it was supposed to.
 

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