PWM..Show us How

[nate456789]

Hello. I am pretty handy but cant solder

Could i use this PWM off Amazon

Video Link: http://www.amazon.com/Dimming-Controller-LED-Lights-Ribbon/dp/B003L4KKF2/ref=sr_1_2?ie=UTF8&qid=1319919860&sr=8-2

Or just use the one recommended on the thread.

Also what size SSR is recommended. Found a 40A and a 25A which is better for this application.

Rock Chalk

Chris

Go with 40 amp. These are the cheapest priced one I found. I bought 2 with heat sinks for the price of one with heat sinks on the other sites.
http://www.oscsys.com/40A-Solid-State-Relay-SSR.html

Bakatronics has the option to buy the PWM board assembled for like a few bucks more. I would go that route.

 

[Walker]

That PWM you linked to will not work without modification. It's meant to use as a dimmer for LEDs so it will be turning on and off REALLY fast. You'd need to slow it down to get it to work right for out application.

 

[Homercidal]

Hello. I am pretty handy but cant solder

Could i use this PWM off Amazon

http://www.amazon.com/dp/B003L4KKF2/?tag=skimlinks_replacement-20

Or just use the one recommended on the thread.

Also what size SSR is recommended. Found a 40A and a 25A which is better for this application.


Rock Chalk

Chris

YOu can find those FK804 circuits prebuilt. I'm currently collecting all of the parts I need to make them myself, including printing my own circuit boards. I want to make a bunch, but can't see paying full price for all of them when I can probably build them for like $4 each.

I could probably have made a complete board this weekend if I hadn't gotten way too busy.

 

[clearwaterbrewer]

Why make a complete board that you have to mount somewhere? The components (a 555 and a cap) are small enough to mount to the back of the Potentiometer.. (see my video on page 5 of this thread..)

 

[Homercidal]

Why make a complete board that you have to mount somewhere? The components (a 555 and a cap) are small enough to mount to the back of the Potentiometer.. (see my video on page 5 of this thread..)

This is true, but the FK804 is a pretty small board and comes already attached to the pot, so placement is not a problem.

I'll have to build them both and see if there is any difference in the performance between them.

 

[ezzieyguywuf]

I too would like to know what the benefits/detriments of using the FK804 over clearwaterbrewer's 'hack' are. To Walker's point, "less stuff = more betterrer", but my engineering curiosity has me wondering why the manufacturers of the FK804 included all that extra 'stuff'.

 

[Homercidal]

I too would like to know what the benefits/detriments of using the FK804 over clearwaterbrewer's 'hack' are. To Walker's point, "less stuff = more betterrer", but my engineering curiosity has me wondering why the manufacturers of the FK804 included all that extra 'stuff'.

It's quite possible that the FK804's "extra" stuff is more better for controlling a DC fan, than for firing a relay. I don't know enough about electronics to understand it. I know how to use a soldering iron, and know what some components are and what a very few of them actual do.

I'm curious to know if the simple 555 timer and cap circuit actually does PWM, or is just a timer...

 

[Walker]

I'm curious to know if the simple 555 timer and cap circuit actually does PWM, or is just a timer...

it actually does PWM.

You set a fixed period/frequency for the circuit by selecting the size of the potentiometer and the size of the controlling capacitor. Adjusting the potentiometer then lets you adjust the width of the pulse that is generated by the circuit. You can adjust between 0% of your fixed timing period and 100% of your fixed timing period.

 

[passedpawn]

I'm curious to know if the simple 555 timer and cap circuit actually does PWM, or is just a timer...

Look up datasheets or the zillion 555 circuit web pages. "Astable" or multivibrator is the mode you want, same as PWM. "One-Shot" is the term for when it is set up for one timed pulse.

 

[Walker]

you said "vibrator".

huh-huh.....

 

[Homercidal]

Ok, I did a google search for one shot and vibrator. It's been a while, and I don't see myself finding any electronic information for a few more hours...

Seriously, I don't know that I would understand any of the technical papers. I've tried learning electronic theory, and it still seems to elude me. What I need is personal tutoring, from what resistors and capacitors do, to how they are used in a circuit.

At any rate, I'm collecting parts for stirplate builds, and I can use some of those for making these simple circuits for BK use just fine as well.

 

[Walker]

Ok, I did a google search for one shot and vibrator. It's been a while, and I don't see myself finding any electronic information for a few more hours...

Seriously, I don't know that I would understand any of the technical papers. I've tried learning electronic theory, and it still seems to elude me. What I need is personal tutoring, from what resistors and capacitors do, to how they are used in a circuit.

At any rate, I'm collecting parts for stirplate builds, and I can use some of those for making these simple circuits for BK use just fine as well.

Resistors limit the flow of current. You can sort of think of it like a ball valve. The lower the resistance (more OPEN the valve is), the more current you get flowing. The higher the resistance (more CLOSED the valve is) the less current you get flowing.

In this application, the capacitor can be though of as a bucket. The larger the capacitor (the larger the bucket), the longer it takes to charge (fill) it up. The smaller the capacitor (smaller the bucket), the less time it takes to charge it up.

The 555 timer in a PWM circuit is like some dude sitting there whose job is to wait for the bucket to fill up from the hose, and then dump that bucket down a drain.

So, you pick a bucket size (the large controlling capacitor). You get a couple of valves (the two sides of the potentiometer). Turning the potentiometer one way makes the feeding hose flow faster (opens it's valve more) at the same time as making your draining hose flow slower (closes it's draining valve more). Turning the potentiometer the other way makes the feeding hose flow slower while making the draining hose flow faster.

You now have your circuit.

water flows in and fills up the bucket. when the bucket is full, the dude dumps it down the drain. You are in control of how fast vs how slow the bucket can be filled as well as how fast or slow the bucket can be dumped.

The whole time the guy is busy dumping water down the drain, the SSR is enabled.

So, if you make the bucket fill slowly, the SSR is off the whole time it is filling. Then you give the guy a HUGE drain to dump the bucket down, which takes basically zero time, so the SSR never gets a chance to be enabled.

Twist the valves the other way.

The bucket fills up REALLY fast (like... INSTANTLY), but the guy takes a long ass time to dump it down the small drain, so the SSR is on for a long time.

Set the values to the middle position.

Bucket fills up at a reasonable rate, and it can be dumped at a reasonable rate. SSR is enabled half of the time.

 

[nate456789]

Nice explanation. Just glad he didn't ask what the diodes and the transistor do. That would really confuse him.
My thoughts on the Bakatronics circuit vs just the 555 and a resistor and cap, is the bakatronics circuit is more stable. Not that this application is that critical.

 

[Walker]

Nice explanation. Just glad he didn't ask what the diodes and the transistor do. That would really confuse him.
My thoughts on the Bakatronics circuit vs just the 555 and a resistor and cap, is the bakatronics circuit is more stable. Not that this application is that critical.

Diodes are check-valves - one way flow.

I don't have any transistors in my PWM design. Not necessary if you are driving an SSR with the PWM.

edit: I am pretty sure that the bakatronics PWM is just a 555 and pot and cap anyway, so I don't know why you would consider it "more stable". ???

From a previos post, you can see the bakatronics schematic:

The transistor is there to help with current load, which is necessary for controlling a DC motor, but not for controlling an SSR. The other two diodes in the schematic are for circuit protection I think.

 

[clearwaterbrewer]

I thought I would throw out pics and the latest schematic for my tiny PWM..

here is the latest schematic, I added the diode which helped get my 'off' times below 25%, and I added the cap on the CTRL pin, not sure it really helped.. (not shown in schematic is that these Potentiometers come with a 'off' position that shuts off a separate sets of contacts. I used this to switch off the 12V completely)


http://c.circuitbee.com/build/r/schematic-embed.html?id=0000000194

Here are installed pics, I am very happy with using them to control a boil or RIMS heat.

and the front view, knob placed below my HOA switches

 

[Homercidal]

I already knew what I diode does, and I think the transistor depends on which type you use... Not really sure about that one.

Walker, your description still makes it sound like an on/off switch with a timer, rather than modifying a waveform. At least that is what a PWM does in my head. Changes the amount of time a waveform spends in the up postition, in relation to the amount of time it spends in the down position, looking at it in it's wave.

So you are saying that the simple circuit keeps the waveform high for the entire several seconds (or whatever)?

 

[clearwaterbrewer]

Ok, I did a google search for one shot and vibrator. It's been a while, and I don't see myself finding any electronic information for a few more hours...

Wiki to the rescue to show what you really need!

Google: astable multivibrator 555

http://en.wikipedia.org/wiki/555_timer_IC

read the Astable section, including the very last line... replace those two resistors with a potentiometer and add in that diode and you have what I made...

 

[Walker]

Walker, your description still makes it sound like an on/off switch with a timer, rather than modifying a waveform. At least that is what a PWM does in my head. Changes the amount of time a waveform spends in the up postition, in relation to the amount of time it spends in the down position, looking at it in it's wave.

Your understanding of a PWM is correct, but your understanding of the simple circuit is not.

So you are saying that the simple circuit keeps the waveform high for the entire several seconds (or whatever)?

No. The simple circuit allows you to adjust the percentage of time that the waveform is high.

In my bucket filling/dumping analogy, the waveform is "high" while the guy is dumping the bucket down the drain. The waveform is "low" while waiting for the bucket to fill up.

The potentiometer allows you to adjust anywhere between two extreme settings.
- bucket fills instantly, but drains slowly => waveform is "high" 100% of the time.
- bucket fills slowly, but drains instantly => waveform is "low" 100% of the time.

You can turn the potentiometer to set it somewhere between these two extremes. For example, put the pot in the middle setting:
- bucket fills up in the same amount of time that it takes to drain the bucket => waveform is "high" only 50% of the time.

 

[nate456789]

edit: I am pretty sure that the bakatronics PWM is just a 555 and pot and cap anyway, so I don't know why you would consider it "more stable". ???

It's been 20 yrs since I have messed with 555 circuits, but I think D1 and D2 Switching diodes help keep the trigger and threshold pins at a constant reference voltage. Making the circuit more stable against noise on the line voltage. Like from a DC motor and such.
Just a guess.

 

[Walker]

It's been 20 yrs since I have messed with 555 circuits, but I think D1 and D2 Switching diodes help keep the trigger and threshold pins at a constant reference voltage. Making the circuit more stable against noise on the line voltage. Like from a DC motor and such.
Just a guess.

D1 and D2 are there for the charge and discharge of the C1 cap. You want to enforce that draining the cap happens through one side of the potentiometer and the charging the cap happens through the other side of the potentiometer.

I think you meant to say "D3 and D4"? I do think those are there for some reason related to controlling a DC motor, just like the transistor is - maybe noise cancelling or something.

Since the DC motor aspect of it is irrelevant for controlling the SSR, the simple circuit is pretty much the same as the bakatronics one, minus some components you don't need for our application.

less stuff = more betterer

 

[nate456789]

Since the DC motor aspect of it is irrelevant for controlling the SSR, the simple circuit is pretty much the same as the bakatronics one, minus some components you don't need for our application.

less stuff = more betterer

I agree - I should have gone with the setup clearwaterbrewer has. Looks pretty slick and everything is out of the way.

 

[mabrungard]

Even though the example for the on/off cycling shown much earlier in this thread looked like a waveform, it was just a DC on/off trace. There is no wave in DC. This PWM controller is producing a pulsed DC voltage to serve as the input signal for a SSR with DC input and AC output. The SSR does not care if the DC voltage has any sort of varying voltage. It only cares that the signal voltage is above the SSR's trigger voltage (AC output on) or the signal voltage is below its trigger voltage (AC output off). Varying the voltage of the DC signal would not alter the AC power through the SSR.

 

[clearwaterbrewer]

I agree - I should have gone with the setup clearwaterbrewer has. Looks pretty slick and everything is out of the way.

Thanks... I am trying to work my way through Ki-Cad to get a miniature PCB designed that the 5-pin Pot solders to, and holds the 555, diode, and 2 caps.. and ideally has small screw terminals to wire +, -, and ssr output to...

 

[lschiavo]

I thought I would throw out pics and the latest schematic for my tiny PWM..

Here are installed pics, I am very happy with using them to control a boil or RIMS heat.

I like this idea for a switched pot and piggyback circuit. Looks like a little hot glue used too? I love that stuff for insulating components and holding things together.

I built three of these for boil control so far. I always put an LED near the contol knob that just mirrors the SSR LED. I like the feedback to know the circuit is working plus it is a visual indicator of the set boil level. And flashy lights are cool

 

[Homercidal]

I think some of this is starting to sink in. I'll want to read up again on DC current and of course now you've gotten me more interested in learning electronics again. I need to find someone who can give simple tutorials. Add it to my lists of interests.

I since I have so many 555 timers, I wonder how I can incorporate one into a circuit to create an LED light pattern that sweeps across, like a Cylon, or KITT... That would be sweet.

 

[lschiavo]

LED light pattern that sweeps across, like a Cylon, or KITT... That would be sweet.

I have a failed attempt at this still on my breadboard from years back. I think I used a shift register but could not get it to reverse direction smoothly. This would be cool to have on a control panel!

 

[Homercidal]

I have a failed attempt at this still on my breadboard from years back. I think I used a shift register but could not get it to reverse direction smoothly. This would be cool to have on a control panel!

I am pretty sure I've seen such a circuit on the Mustang forums before... Some people built them when Mustang owners replaced their tali lights with the sequential lights from the Cougar. Also used in some of the Shelby Mustangs I believe.

Modern electronics allowed use of LED lights, so people started replacing their incandescent bulbs with LEDs and rigging up the sweep (1-way) circuit. I think I saw some variations that made them act like KITT.

 

[Homercidal]

http://www.bit-tech.net/modding/2002/06/22/knight_rider/2

First google hit. There's even a printed board drawing so you can etch your own boards easily.

It's old, and there's mention of having to substitute a part or two, but I think it's doable.

 

[lschiavo]

http://www.bit-tech.net/modding/2002/06/22/knight_rider/2

First google hit. There's even a printed board drawing so you can etch your own boards easily.

It's old, and there's mention of having to substitute a part or two, but I think it's doable.

Cool. Looks like the lm3914 is about $2-3. I will have to get a few on my next order.

 

[Homercidal]

There are a few of these circuits out there. If I get time enough I'll look at a few more. I had time earlier while testing a data recovery software. At this time I have no good excuse to surf the net. Maybe I can find one more drive to test...

 

[clearwaterbrewer]

....I always put an LED near the contol knob that just mirrors the SSR LED. I like the feedback to know the circuit is working plus it is a visual indicator of the set boil level. And flashy lights are cool

The HOA switch on the front has a LED in it that provides that but is powered from 120VAC so I see when it is actually firing the element, not just the SSR..

 

[lschiavo]

The HOA switch on the front has a LED in it that provides that but is powered from 120VAC so I see when it is actually firing the element, not just the SSR..

Good idea. Same function one less component.

 

[Cromwell]

So, correct my thinking if you will?

A PWM controller is a way to turn the heat up or down on the heating element, like turning the stove up or down.

Whereas a PID tries to turn off and on the heating element to achieve a specific temperature.

Would using a PID in conjunction with a PWM allow more precise control of temperature, by fine-tuning the amount of heat you add based on the Differential?

 

[Homercidal]

So, correct my thinking if you will?

A PWM controller is a way to turn the heat up or down on the heating element, like turning the stove up or down.

Whereas a PID tries to turn off and on the heating element to achieve a specific temperature.

Would using a PID in conjunction with a PWM allow more precise control of temperature, by fine-tuning the amount of heat you add based on the Differential?

A PID is great for heating mash or sparge water because it turns on and off in order to hit a set temperature, with whatever variables you tell it (overrun, max cycle, etc) if it can.

A PWM is a great way to run an electric heating element because it doesn't care about temp, it only runs on time. Essentially you are turning the element on and off at a rate to control the boiling of the wort. By turning it off and on like that, it heats up a bit less or a bit more.

You don't need temperature control for boiling wort, but having the ability to adjust the rate of boil might be nice to prevent boil-overs, scalding, etc..

 

[P-J]

A PID is great for heating mash or sparge water because it turns on and off in order to hit a set temperature, with whatever variables you tell it (overrun, max cycle, etc) if it can.

A PWM is a great way to run an electric heating element because it doesn't care about temp, it only runs on time. Essentially you are turning the element on and off at a rate to control the boiling of the wort. By turning it off and on like that, it heats up a bit less or a bit more.

You don't need temperature control for boiling wort, but having the ability to adjust the rate of boil might be nice to prevent boil-overs, scalding, etc..

The really nice thing about the Auber Instruments PID SYL-2352, when set it to manual mode, you can control the percent of power delivered to the element so that you can control the boil very well.

One PID and all of the control functions delivered in one package.

No?

 

[Homercidal]

The really nice thing about the Auber Instruments PID SYL-2352, when set it to manual mode, you can control the percent of power delivered to the element so that you can control the boil very well.

One PID and all of the control functions delivered in one package.

No?

That's interesting. I've not looked too closely at them. I've got like 5 of the basic Love style controllers from work, so I have no reason to shop around.

If you use a 220V heating element you might still need a relay, and the simple PWM circuit could be made for like $5 and works like a charm from what I've seen. (I've yet to try it).

Frankly, I think I'd prefer them to be separate circuits. The PWM element control might be easier to operate than switching the PID to manual and adjusting the element with the buttons. Flipping a switch and turning a dial just seems more natural to me.

Also, since the PID is likely in the MLT or HLT for controlling the mash temp, you'd have to switch it over to the BK for boiling and there would be a switch involved at least, depending on the wiring.

It would probably work. Maybe just feel different adjusting the boil with buttons.

 

[P-J]

...
It would probably work. Maybe just feel different adjusting the boil with buttons.

Fine. Just do it your way.

done.

P-J

 

[lschiavo]

Sheesh Homer! You shure are feisty today. Quit p1$$ing everyone off eh?

 

[Homercidal]

Hm... I didn't think I was feisty, just stating some facts and opinions. It was clear in my head that if you wanted to use buttons to adjust the element that would work. Personally, for the simplicity and cost of the circuit, I'd rather have a knob.

Maybe that's not what the post sounds like to others? I certainly meant no insult or anything. Just trying to hold a useful conversation.

But while we're on the subject, I'd like to point out that a PID is great for a recirc system, but if you're just heating up some water to mash with, or to boil with, that simple PWM circuit would suffice by itself. Just something to think about.

 

[jsguitar]

A lot of us use a PID that has a manual control mode that simply allows you to hit a button on the PID to switch to manual mode. You just hit a switch for power to go to the boil kettle, then hit the PID's manual button and set the percent of power where you want it. It doesn't need an additional probe for the manual mode to function, so it's easy to setup if you're already using a PID to control your HLT. Many of us here do it that way since we were already buying a PID anyway.

Nothing wrong with controlling the HLT with a PWM at all except that you have to watch the temp carefully, so if someone's already using a PID for that, they can also use it to control the BK without needing to build the PWM. Just a different way to skin the same cat.