Simple PWM Stirplate Controller

[Jackjama]

I built this on a bread board using the values on the front page. My fan goes from a medium speed to a fast speed. I need to get it to go slower. Either i have hooked something up wrong or i need some different values on some of my components.

I have double checked the drawing and i fell like everything is connected correctly. I used the values on the drawing. The only doubt i have is the capaciter. The capaciter has a long wire and short wire. I hooked the short wire to ground and the long wire to terminal 6. Is this correct? The data sheet said the long wire is positive.

I am guessing i need to go up on either r2 or c1. Any suggestions?

 

[nmfree]

The only doubt i have is the capaciter. The capaciter has a long wire and short wire. I hooked the short wire to ground and the long wire to terminal 6. Is this correct? The data sheet said the long wire is positive.

That's correct.

I built this on a bread board using the values on the front page. My fan goes from a medium speed to a fast speed. I need to get it to go slower. Either i have hooked something up wrong or i need some different values on some of my components.

I am guessing i need to go up on either r2 or c1. Any suggestions?

Before you start changing anything, I'd suggest you finish mocking up the whole thing (glue your magnet to the fan, etc.) and actually try it out with your flask/jar/vessel and your stir bar. Right now with no load the fan might seem to be spinning too fast, but the added mass of the magnet, the stir bar, and the liquid in the flask will help slow the motor down.

If after testing your set up the fan is still spinning too quickly, then you can try adding resistance in series with R2 or try Kaiser's modification a few posts up.

 

[Jackjama]

Thanks i will finish building before i do anything.

 

[Kaiser]

changing the way the capacitor is charged and drained is key to be able to change the pulse width from 0 to 100%. I ended up building it like this:

you need one more diode but don't need R1.
It works like a charm.

Kai

 

[Jackjama]

I will give this a try. I currently have my stirplate to where it goes slow enough to use. However it does not turn off completely.

What is the purpose of sinking both the .1 and 22 mf capacitors from the source to ground?

 

[Kaiser]

What is the purpose of sinking both the .1 and 22 mf capacitors from the source to ground?

That's to stabilize the input. You may not need it. RocketMan mentioned this in one of his posts.

Kai

 

[DSmith]

These are avaiable for $10 shipped on ebay:

http://www.ebay.com/itm/12V-40V-10A...302?pt=LH_DefaultDomain_0&hash=item1c2925822e

I bought the one in the link above, in a build with a 18V power supply, 40V fan & (2) 20lb pull disc magnets.

 

[tommyturbo]

how would you go about adding a power supply to this project?

 

[tommyturbo]

well, heres my take on it so far...



Let me know what you think

 

[cheesenips]

Bumping this old thread, hopefully someone's can help me out.

The mosfet linked by op is not made anymore, so does anyone have a part # for an equivalent?

 

[rocketman768]

Bumping this old thread, hopefully someone's can help me out.

The mosfet linked by op is not made anymore, so does anyone have a part # for an equivalent?

Your standard BS170 will probably work.

 

[rkhanso]

I realize this thread is a few months old but here's to hoping someone is around to listen. First let me say thank you Rocketman for sharing such a simple to implement design!

I built upon this design to make a dual-stirplate using identical components to yours with the exception of a 556 dual timer instead of the 555. I wired up each half of the 556 just like your 555 and it's working great with one minor exception.

The only issue I'm having is that if I turn *either* potentiometer knob then *both* fans respond. I can't figure it out as the 556 halves are supposed to be completely isolated with the exception of Vcc and ground. I've triple checked the circuit and aside from the 556 itself there's nothing crossing from one half of the breadboard to the other so I can't figure out why this is happening.

I've attached a wiring diagram for my breadboard in case anyone thinks they can help. Also the higher level circuit schematic in case you need the 556 pinout. This isn't the exact physical wiring of my board in it's final state, but it does match electrically. I made this easy to read, symmetrical version for pre-planning the circuit, but in the final layout I spread the components out and relocated some connection points for easier routing inside my box. Again though, it's electrically representative, just easier to read.

Thanks in advance to anyone that can point out what I've done wrong. If we can figure this out I'd love to post more information about my stir plate in case anyone else is interested in building a double.

Edit: So after posting this I got the idea to study the circuit diagram a bit instead of just studying my breadboard looking for mistakes, and I have a guess at the problem. For the record my capacitors are non-polar electrolytics because that's all Radioshack had. As such I'm guessing the voltage at Pin 2 is bleeding down through the "left" cap, back up through the "right" cap and affecting Pin 10 (or vice-versa). I should be able to prevent this with another pair of diodes, one between each cap and ground, to prevent any flow between those halves. Does that seem to make sense? I think I'll swing back through Radioshack tomorrow to give it a try as I can't see any other method for voltage on one half of the circuit to cross over to the other. If anyone else sees anything please let me know.

I tried making this dual stir-plate that @Magialist shows in the two attachments, and had trouble.

Has anyone else made this dual stir-plate successfully? I'm sure I just have something wired wrong, but I could only get one fan to spin and when I adjusted the Pot, the speed didn't change.

I do see a couple differences between this design and the original post in this thread. There's an additional Resistor in the original post, and an additional diode in this post.

I wanted a dual stir-plate because I'm going to be brewing 10-gallon batches, probably splitting into 2 different fermenting buckets and maybe trying 2 different types of yeast, or simply having enough yeast starter for 10 or more gallons.

I did have the drains isolated from each other both electrically and physically (Not connected at the heat-sink).

I was just hoping for some confirmation the design as-is in the two attachments in the post from @Magialist is correct for a dual stir-plate, even though there are differences between it and the original post.

 

[rkhanso]

I found what I did wrong. I had the Pots wired incorrectly. And, both sides of the 556 work now.
I should have double-checked EVERYTHING first.

 

[monsterbash]

changing the way the capacitor is charged and drained is key to be able to change the pulse width from 0 to 100%. I ended up building it like this:

you need one more diode but don't need R1.
It works like a charm.

Kai

Hi !! It's an old but GREAT and very usefull thread !!!

My diy stir plate is controled by an LM317 and it's frustrating not to be able to rotate the fan at lower speeds.... I read the entire thread and will definetlly try rocketman768's schematic.

I'd also like to make the change proposed by Kaiser (changing the way the capacitor is charged and drained) but, as an eletronic noob, I cannot do that without the schematic/picture and it's not available anymore. Any help ??

Thanks in advance

 

[rkhanso]

Hi !! It's an old but GREAT and very usefull thread !!!

My diy stir plate is controled by an LM317 and it's frustrating not to be able to rotate the fan at lower speeds.... I read the entire thread and will definetlly try rocketman768's schematic.

I'd also like to make the change proposed by Kaiser (changing the way the capacitor is charged and drained) but, as an eletronic noob, I cannot do that without the schematic/picture and it's not available anymore. Any help ??

Thanks in advance

Try this: http://braukaiser.com/wiki/index.php?title=PWM_Coltrolled_Stir_Plate_Design

 

[monsterbash]

Try this: http://braukaiser.com/wiki/index.php?title=PWM_Coltrolled_Stir_Plate_Design

Hey, thank you !!!!
BTW, looking at that design I saw that pin 7 (discharge) from NE555 is not hooked anymore... is that correct ??

Thanks in advance,
Silvio Finotti

 

[rkhanso]

If it's not being used in the schematic, then I'd say no. I haven't actually built this yet.

 

[rkhanso]

Man, I'm really having trouble building this thing. I had a dual stir plate wired up with just one side and it worked....sort of. It only came on at high speed and I could only slow it down a little bit and eventually the fan just stopped spinning. I think I may have poor quality breadboards (cheap, from China).

Then, I fried a 556 chip.

Has anyone successfully built one of of these dual/556 stir plates?