PWM..Show us How

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
I thought they might what I wanted but I wanted to make sure I am getting parts I am not totally sure about.

Thanks for the help Walker and others.
 
does the voltage on the cap matter in clearwaterbrewers design? I have found a 35v, 25v, 50v, 450v.

Thanks everyone.
 
Homer, did you post your process for etching the boards already?

Walker, I ordered 4 kits :) Just because it makes more sense with shipping.

I am using the laser printer method. There are hundereds of articles online. It basically goes like this:

Make layout and print on Laser printer in REVERSE. OR, print on ANY printer and then make copies on a laser copier with darkness set to HIGH.

The idea is to get as much toner on the paper as possible.

Use a green scrubby and alcohol to get the tarnish and oils from some copper clad.

Iron the design onto the board. The plastic toner will stick to the board. Soak the board and paper in water for a while to soften the paper and GENTLY wipe the paper from the board, leaving the layout still attached.

Then soak the board in etching solution until the copper is eaten away. The copper under the toner will remain, leaving traces. Then wipe the toner away with some acetone.

I then "Tin" the traces with a hot iron and some solder.

The etching solution I ended up using is 2 parts Hydrogen Peroxide and 1 part Muriactic Acid (swimming pool/hot tub supply store). The first board will etch in a couple of minutes!

NOTE: this solution is VERY bad for the environment, since it now contains a lot of copper! Please don't pour this stuff down the drain! I've read that it can be used over and over and if the etching isn't working you can just add more peroxide and acid. If you start getting too much you can let it evaporate. (outside, since the fumes are pretty nasty)

Google that stuff.

Last night I finish my first working board. I still need to tweak the process, but it worked out ok I think.

Another tip is to use the cheapest, thinnest, sales ad paper you can find. with a bit of gloss on it. This allows the toner to stick to the OUTSIDE of the paper, and yet it also allows the paper to be removed from the board easily.

It takes a bit of practice to get the print and the ironing done just right. But you can always clean the board with acetone and try again!
 
... The etching solution I ended up using is 2 parts Hydrogen Peroxide and 1 part Muriactic Acid (swimming pool/hot tub supply store). The first board will etch in a couple of minutes!

NOTE: this solution is VERY bad for the environment, since it now contains a lot of copper! Please don't pour this stuff down the drain! I've read that it can be used over and over and if the etching isn't working you can just add more peroxide and acid. If you start getting too much you can let it evaporate. (outside, since the fumes are pretty nasty)
...

Found this in case you're interested ...

Stop using Ferric Chloride etchant! (A better etching solution.)
 

That's the main article I ended up using as a guide after reading a bunch of threads. The copper remains in the etchant, so it's still toxic, but you can re-prime it over and over. Eventually you'll have to find a place to dispose of it, or find a good way to remove the copper and then you can neutralize the acids.

I wonder if a copper plating process could remove most of the copper...
 
That's the main article I ended up using as a guide after reading a bunch of threads. The copper remains in the etchant, so it's still toxic, but you can re-prime it over and over. Eventually you'll have to find a place to dispose of it, or find a good way to remove the copper and then you can neutralize the acids.

I wonder if a copper plating process could remove most of the copper...

Yeah copper plate all your brass fittings ;) hehe... I don't know the real(tm) answer unfortunately.
 
Just finished up mine, with Walkers suggestions. 100k pot, 22uf cap, also added the .01uf cap and a diode

Seems to be working fine. Will probably try it Sunday, once I get it installed it my control box.

Thanks again for the help!!


a3424775.jpg
 
This is how I build them:
PWM1.jpg


I'm looking to build one of these. However, I couldn't find any 1N5818 diodes at Radio Shack. What specs on the diodes am I looking for? I picked up 1N4742A Zener diodes because they said 12-volt and I figured this circuit was 12-volt with the wall wart.
 
A diode, in general, is a one-way valve. Current can only flow in one direction though it. If you try to run current through it in the backward direction, nothing will happen. However, if you apply a large enough voltage to it while trying to get current to run through it backward, the diode will eventually breakdown and let current flow backward. It will probably also overheat and burn up. This breakdown voltage us usually pretty large.

Zener diodes are a special kind of diode. They operate like a diode as described above, but they have a greatly reduced breakdown voltage for the reverse direction, and will not overheat and die when you run them backward. In the case of the zener diodes you bought, the breakdown voltage is 12v.

Sorry for being long winded, but the "one-way" property of the diode is something the PWM circuits rely on. In the case of my schematic, the two diodes ensure that one side of the pot us used to charge the capacitor, and the opposite side of the pot is used to discharge the capacitor.

Your zener diodes will work, but only if you stay below 12v. If you power this with something more than 12v, then the diodes are going to be allowed to let current flow backward, and the thing just won't work right.
 
A diode, in general, is a one-way valve. Current can only flow in one direction though it. If you try to run current through it in the backward direction, nothing will happen. However, if you apply a large enough voltage to it while trying to get current to run through it backward, the diode will eventually breakdown and let current flow backward. It will probably also overheat and burn up. This breakdown voltage us usually pretty large.

Zener diodes are a special kind of diode. They operare like diode as described above, but they have a greatly reduced breakdown voltage for the reverse direction, and will not overheat and die when you run then backward. In the case of the zener diodes you bought, the breakdown voltage is 12v.

Sorry for being long winded, but the "one-way" property of the diode is something the PWM circuits rely on. In the case of my schematic, the two diodes ensure that one side of the pot us used to charge the capacitor, and the opposite side of the pot is used to discharge the capacitor.

Your zener diodes will work, but only if you stay below 12v. If you power this with something more than 12v, then the diodes are going to be allowed to let current flow backward, and the thing just won't work right.

No apologies needed for being long-winded, much appreciated. Since my circuit is being fed with a wall wart that (upon review) has an output of 5V, these diodes should work right? Any other diodes you can suggest from these diodes?
 
Pretty much any of those diodes will work. They have different ratings total amps thay can handle and things like that, but in a PWM, you are working with low current and low voltage, so all is well.
 
Pretty much any of those diodes will work. They have different ratings total amps thay can handle and things like that, but in a PWM, you are working with low current and low voltage, so all is well.

Much appreciated, Walker. I went with one of the 1N4000 series rated for 1A.
 
If the pot you have available is 1/5th the size as the one in the schematic, then you can probably just use a capacitor that is 5 times the size of the one in the schematic and maintain the same timing behavior.

So... 11uF in this case.

But, you could even go larger and still get a reasonable frequency for the PWM. If I am reading/understanding it right, the circuit with the 2.2uF cap and the 500kOhm pot is actually cycling a little too fast (about 1.3Hz).

If I am correct on my calculations, I'd probably throw a 22uF cap in that with the 100KOhm pot and get a frequency of 0.65Hz.

I went with the 22uf on this board. I used it yesterday and it worked fine. But, The pulse width is a just a bit to long. Which way would I go to get it to cycle just a bit faster.

The way it is now I can get a decent boil but it in extremly sensitive between no boil and to agressive with a 4500w element.
 
I went with the 22uf on this board. I used it yesterday and it worked fine. But, The pulse width is a just a bit to long. Which way would I go to get it to cycle just a bit faster.
Make the capacitor smaller. That will speed up the cycle time.

The way it is now I can get a decent boil but it in extremly sensitive between no boil and to agressive with a 4500w element.

This might be a problem with the potentiometer you are using. Some pots are "linear taper" and some are "audio taper". An audio pot is not suitable here because the change in resistance as you turn the knob on the pot moves in a logarithmic curve.

pottaper.gif
 
Hi guys

12V-24V 3A DC Motor Speed Control PWM HHO RC Controller | eBay

12V-24V 3A DC Motor Speed Control PWM HHO RC Controller

I got one of these off ebay. it looks like it has a timer other than a 555; is anyone familliar with this circut? It has a 47 or could be a 4.7uf cap and I was wondering if I would have to change it to work with a ssr.

thanks, Rod

Can you read the number on the chip? They do make a 555 in a double-sized unit. I think it's a 556. It's good if you want to utilize 2 timers on the same circuit, etc.
 
Can you read the number on the chip? They do make a 555 in a double-sized unit. I think it's a 556. It's good if you want to utilize 2 timers on the same circuit, etc.

Yeah, that's exactly what I was thinking. I tried looking at the ebay pics, but I can't read the printing on the chip.

The only weird thing is that (if it actually is a double 555), both halves of it seem to be in use. (?)
 
Exactly.

I think that was designed for a train set. Not sure what that would have to do with anything. Plenty of current to operate an SSR. Way overkill.
 
Can you read the number on the chip? They do make a 555 in a double-sized unit. I think it's a 556. It's good if you want to utilize 2 timers on the same circuit, etc.

There isn't any number on the chip. I picked this up real cheap and figured I might be able to use it. I'v got about all the parts to build some on walker's design, but I got this so cheap I couldn't pass it up.
This stuff has really came down in price compared to a few years ago. I used to build coonhunting lights and a dimmer switch about like Walker is building cost me about $30.00. I didn't know what it was at the time, but now that I've seen all these circuts I'm pretty sure it was a 555 timer.

thanks; Rod
 
My setup is a little different. I am using a BCS controller, and want to be able to use the PWM when I switch away from the BCS.

Sorry for the cruddy rework of the image, but can anyone tell me if I am on the right track with this setup.

mypwm.jpg
 
This might be a problem with the potentiometer you are using. Some pots are "linear taper" and some are "audio taper". An audio pot is not suitable here because the change in resistance as you turn the knob on the pot moves in a logarithmic curve.

Audio pot is exactly what I used.. I ll order in a linear taper one and give it a go.

Thanks again
 
My setup is a little different. I am using a BCS controller, and want to be able to use the PWM when I switch away from the BCS. [br][br]
41355d1324604349-pwm-show-us-how-mypwm.jpg
[br][br]
Sorry for the cruddy rework of the image, but can anyone tell me if I am on the right track with this setup.


One thing I noticed in your re-design is that you are now cutting off a 12V DC signal on the top side and 12V from the low side? Since the heater needs a closed loop circuit from -120 to the +120, if you cut off one side, you will be fine. This is why the original circuit cut off the 120V going to the SSR.

With your implementation you always have +120 going from the Relay to the hot side, and -120 connected to the SSR, which will leak even when off, so there will be a small closed connection and the coil will heat up.

For this reason, I would suggest that you not cut off the 12V DC, or if you do, use a switch, and keep the relay where it was.

-Lorg
 
One thing I noticed in your re-design is that you are now cutting off a 12V DC signal on the top side and 12V from the low side? Since the heater needs a closed loop circuit from -120 to the +120, if you cut off one side, you will be fine. This is why the original circuit cut off the 120V going to the SSR.

With your implementation you always have +120 going from the Relay to the hot side, and -120 connected to the SSR, which will leak even when off, so there will be a small closed connection and the coil will heat up.

For this reason, I would suggest that you not cut off the 12V DC, or if you do, use a switch, and keep the relay where it was.

-Lorg

Also, the green cord shouldn't go to ground, that will kill your GFI It is still either a hot or a neutral, it terminates on the selector side of the SSR, no tying to ground or neutral needed.

*EDIT*
Saw another thing. Right now the Relay shows one always on.. tying the BCS to the output of the PWM... which makes the PWM usless, and the Relay essentially useless, as you show it is connected all the time...
 
I ordered the kit from bakatronics, got a soldering iron and 2.2 capacitor from the shack. ready to try this soon. Now to work out the rest of the needed goodies.
 
Sure, but where's the fun in that?

All kidding aside, a re-purposed computer power supply can come in handy for small electric projects.
 
Has anyone added an LED to the output of the PWM for visual display of the output? Where did you connect it and did you need any other components? I'd like the light to be dim when the PWM is dialed down and bright when it is at full power.
 
With your implementation you always have +120 going from the Relay to the hot side, and -120 connected to the SSR, which will leak even when off, so there will be a small closed connection and the coil will heat up.

SSRs only leak a few miliamps of current. The heating element will not get hot from this.
 
Has anyone added an LED to the output of the PWM for visual display of the output? Where did you connect it and did you need any other components? I'd like the light to be dim when the PWM is dialed down and bright when it is at full power.

I have an LED attached to the output of my PWM, connected basically to the exact same wires that go to the SSR.

However, this is not going to give you the type of visual indicator that you described. The LED blinks off and on indicating when the heating element is or is not actually producing heat.

A PWM is not really a 'dimmer'... it rapidly cycles things off and on. If you cycled the PWM very VERY fast it might give the appearance of a dimmed LED indicator, but you can't cycle a heating element that fast through an SSR.

I don't know off-hand how you would a light than dimmed based on the PWM's sloooow ON/OFF output. That would possibly be complicated and add a lot of junk to the design.
 
SSRs only leak a few miliamps of current. The heating element will not get hot from this.

I agree. Even at 240v, my LED indicator lamps on the output side of my SSRs will light dimly. But when I plug the element in, the LEDs stay unlit until the SSR is triggered. So, I know there is a small leakage current through the element. The element does stay cool unless the SSR is triggered.
 
I have an LED attached to the output of my PWM, connected basically to the exact same wires that go to the SSR.

However, this is not going to give you the type of visual indicator that you described. The LED blinks off and on indicating when the heating element is or is not actually producing heat.

A PWM is not really a 'dimmer'... it rapidly cycles things off and on. If you cycled the PWM very VERY fast it might give the appearance of a dimmed LED indicator, but you can't cycle a heating element that fast through an SSR.

I don't know off-hand how you would a light than dimmed based on the PWM's sloooow ON/OFF output. That would possibly be complicated and add a lot of junk to the design.

Thanks, Walker, those were my suspicions. I didn't know if there was a way to flatten the wave and have it represent the percentage of the cycle that the PWM is on. So if the wave is 100% on for the cycle, the full 5V would output to the light. If the wave was 50% on for the cycle, then only 2.5V would output to the light. At 25% on, 1.25V would output.
 
okay, pwm came in the mail from bakatronics.

looking at it I feel like I'm back in organic chemistry looking at nomenclature for the first time. I haven't eaten lately and just got back from a 4.5 mile run so I will tackle the project again tonight once I have had a few beers.

anyone have a photo of an assembled board in detail? none of the photos on here work any more
 

Latest posts

Back
Top