PWM..Show us How

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Double-R

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Been looking an waiting, Pretty sure i'm not the only one wondering,
how do you build/make one. Some say get a PWM , you dont need a PID setup . SO I ask . HOW..​
 
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Buy this: http://www.bakatronics.com/shop/item.aspx?itemid=383
Replace C1 with a 2.2uF capacitor to lower the frequency.
Use a 12V wall wart as a power supply to the PWM board.
Connect the output of the PWM board to a SSR to control your boil.

This is how I did it and I'm very happy. Cheap, easy, responsive control.
Can you show photo's of your unit with the wiring schematic:ban:
 

freddyb

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Can you show photo's of your unit with the wiring schematic:ban:
Here's a diagram I made. I tried to keep it simple. Hopefully it's enough to get you going. It's easier to understand once you get your hands on this stuff and start piecing it together.

 

Homercidal

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I have one of those PWM boards and it was very easy to build. I connected to a 12V and watched it smoothly run from Zero to full speed through the whole range of the dial.

Adjusting for a heater element is extremely easy.

Once the board is built, and you have your 12V connected, simply run the output to a Solid State Relay, and connect the Relay to the heater element.

The PWM controller turns the relay on and off faster for more heat, and slower for less. Think of it as controlling PULSES of electricity to the element. The faster the pulses come, the hotter the element will get.
 

Inodoro_Pereyra

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The PWM controller turns the relay on and off faster for more heat, and slower for less. Think of it as controlling PULSES of electricity to the element. The faster the pulses come, the hotter the element will get.

Hmmm...no. A real PWM controls the heat by varying the time the element is active, in relation with the total pulse time. The pulse frequency never changes. What changes is the part of the total pulse the element is receiving power. The wider the active part of the pulse, the more heat produced (hence the "pulse width modulation" name).
 

wyzazz

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^^What he said^^

The PWM doesn't modify the amount of heat the element puts out, that is static based on the wattage/voltage. It just modifies the amount of time the element stays on.
 

Homercidal

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Yeah, now that I re-read my post I have no idea why I posted it like that. I guess that's what happens when you are trying to install Exchange Server and figure Mash Adjustments while reading and posting on HBT...

The image above has a very good sample of the frequency showing the hotter vs the cooler pulse widths. It's more about the time per pulse that the element is on vs the time per pulse that it's off.
 

wyzazz

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Yeah, now that I re-read my post I have no idea why I posted it like that. I guess that's what happens when you are trying to install Exchange Server and figure Mash Adjustments while reading and posting on HBT...

The image above has a very good sample of the frequency showing the hotter vs the cooler pulse widths. It's more about the time per pulse that the element is on vs the time per pulse that it's off.
I feel ya, I'm in the middle of putting a new Barracuda Backup server right now. :mug:
 

vballdrummer

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Be careful here. I know some might argue the HBT board goes a bit overboard when it comes to safety, but is that really possible when we're using water, metal tanks and 30-50 amps at 115 to 230 V?

Specifically, the following concerns on the discussed schematic.
  1. There is no ground shown. ALWAYS use ground; no exceptions -- this absolutely should be shown on any schematic we post.
  2. Once the DPDT is switched ON, you'll have 120V at the element. This combined with no ground to the tanks could make for a very bad brewing day.
 

freddyb

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Be careful here. I know some might argue the HBT board goes a bit overboard when it comes to safety, but is that really possible when we're using water, metal tanks and 30-50 amps at 115 to 230 V?

Specifically, the following concerns on the discussed schematic.
  1. There is no ground shown. ALWAYS use ground; no exceptions -- this absolutely should be shown on any schematic we post.
  2. Once the DPDT is switched ON, you'll have 120V at the element. This combined with no ground to the tanks could make for a very bad brewing day.

Good point! Grounding the element/kettle to the house wiring is essential. I'll need to update the diagram.

And yes, DPDT switch should only be ON when you want the element to be ON. This is manual control.
 
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vballdrummer said:
Be careful here. I know some might argue the HBT board goes a bit overboard when it comes to safety, but is that really possible when we're using water, metal tanks and 30-50 amps at 115 to 230 V?

Specifically, the following concerns on the discussed schematic.

[*]There is no ground shown. ALWAYS use ground; no exceptions -- this absolutely should be shown on any schematic we post.
[*]Once the DPDT is switched ON, you'll have 120V at the element. This combined with no ground to the tanks could make for a very bad brewing day.
Thanks vballdrummer!!
 

vballdrummer

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Just points for any unsuspecting members that grab up a schematic for a blind build. Some of the questions in the Electric Brewing thread are causes for concern.

For noobs, the element is HOT (electrically speaking) even thought the PWM circuit is turned all the way down (off)

Let's go brew!
 

Tuzlo

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Here's a diagram I made. I tried to keep it simple. Hopefully it's enough to get you going. It's easier to understand once you get your hands on this stuff and start piecing it together.


Do you really need a 40 A SSR. I plan on using 240 V 4500 W heater. The math says 18.75 A Max, with a 25% safety margin can you not use a 25 A SSR?
 

wyzazz

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You don't NEED a 40A SSR but it will operate much cooler than a 25A SSR, and for the difference in price it's great peace of mind.
 

Chemkrafty

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How did you wire up the wall wart adapter? Did you take it apart or just wire to the prongs? That part has me confused.
 

onthekeg

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Cut the end that plugged into the phone or whatever and solder that to the input of the board.
 

Chemkrafty

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I guess I should have been more clear. It appeared in the wiring diagram that one leg of the 240 amp service was feeding the wall wart. Was this wired up to an outlet that is plugged in or directly to a transformer? I was hoping to attach my toolbox to the 240 and do all the wiring inside, so I was curious if there was a preferable/safer option.
 

gregdech

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For those of you who have used the bakatronics controller as suggested by freddyb, do you know what the duty cycle is for the base kit? Freddyb suggested switching out one of the capacitors, how does that affect the duty cycle and why is it necessary? Thanks for the input.

Cheers,

Greg
 

flatulentfox

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For those of you who have used the bakatronics controller as suggested by freddyb, do you know what the duty cycle is for the base kit? Freddyb suggested switching out one of the capacitors, how does that affect the duty cycle and why is it necessary? Thanks for the input.

Cheers,

Greg
Bump for an answer. Anyone with this kit and a 'scope that could figure out the pule frequency for us? I would like to know the same thing.

P.S.
the duty cycle is not what is changed by the cap, the pot changes the duty cycle which is what we use to regulate heat output. the frequency of the pulse is what is in question.
 

onthekeg

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I guess I should have been more clear. It appeared in the wiring diagram that one leg of the 240 amp service was feeding the wall wart. Was this wired up to an outlet that is plugged in or directly to a transformer? I was hoping to attach my toolbox to the 240 and do all the wiring inside, so I was curious if there was a preferable/safer option.
The PWM is powered from 120v which the wall wort is plugged into. The 240v has one leg straight to the element, and one leg goes through the SSR. There are four connections on the ssr. Two from the PWM, (the control side) and one leg of the 240v goes in one one side of the SSR and out the other to the element.
 

agezzi

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Buy this: http://www.bakatronics.com/shop/item.aspx?itemid=383
Replace C1 with a 2.2uF capacitor to lower the frequency.
Use a 12V wall wart as a power supply to the PWM board.
Connect the output of the PWM board to a SSR to control your boil.

This is how I did it and I'm very happy. Cheap, easy, responsive control.
were can i find the 2.2uf capactior at? thanks

edit: will this work( http://www.radioshack.com/product/i...Name=Type&filterValue=Electrolytic+capacitors )
 

JKoravos

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Bump for an answer. Anyone with this kit and a 'scope that could figure out the pule frequency for us? I would like to know the same thing.

P.S.
the duty cycle is not what is changed by the cap, the pot changes the duty cycle which is what we use to regulate heat output. the frequency of the pulse is what is in question.

I'd like to know the pulse frequency as well, as it can affect the life of the SSR. The SSRs will fail after a certain number of switches (although much higher than a mechanical relay).

For controlling a heating element, I would guess a few Hz is more than enough to keep a smooth boil. If the speed control is pulsing at 1kHz it's just unnecessarily wearing the SSR.


EDIT: Success! 264Hz in the stock specification. The calculation to adjust the frequency is in the PDF. 2.2uF at C1 gives you 1.2 Hz pulse frequency. I would guess that's very appropriate.

EDIT2: I just bought one. Hopefully it will do a good job replacing the mechanical timer relay which never really worked as I intended.
 

Homercidal

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stlbeer

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Watching this thread.

I was able to buy pretty much the same PWM kit locally for $7.00, so it's worth a try. I also got the 2.2uF cap for C1 replacement.

Hope to put it together tonight.

If anyone wants pics, let me know.
 
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Can you post the model/part number of the transistor? I want to try to build one in a super small package, like inside a 2" long piece of 1/2"-3/4 PVC, and put the pot in the end, mount behind panel door for my Hand-Off-Auto switches to have Variable-Off-Auto :)
 
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Any npn BJT will work there as long as it is can dissapate the load. For that matter, a n-channel FET would work as well (make sure you have that diode across the load if you're driving a mechanical relay coil). TO220 pkg will be good for any relay, mechanical or SSR.

Radio shack will definitely have something to drop in there.
 
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Here is one I have working with a grand total of 3 components:

555
2.2uf cap
500k pot

It has about a 1Hz rate

I have it working now for 2 hours, and am letting it run overnight to test stability, but the package does not get any smaller than this...


CircuitBee drawing

anyone have a quick way I can get the imbedded code below to have the drawing show up here?
<iframe width='500' height='350' frameborder='0' src='http://c.circuitbee.com/build/r/schematic-embed.html?id=0000000094'></iframe>
 

wyzazz

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Here is one I have working with a grand total of 3 components:

555
2.2uf cap
500k pot

It has about a 1Hz rate

I have it working now for 2 hours, and am letting it run overnight to test stability, but the package does not get any smaller than this...


CircuitBee drawing

anyone have a quick way I can get the imbedded code below to have the drawing show up here?
<iframe width='500' height='350' frameborder='0' src='http://c.circuitbee.com/build/r/schematic-embed.html?id=0000000094'></iframe>
Interesting, care to share a pic of how you've got it packaged? I'm intrigued.
 
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