FEATURED Building PWM Controller for 4 wires PWM fan

[Arkade]

I'm Serious, burned a large part of my arm. I was wondering why Demetori wasn't making them and asked me. Thats why. School was weird for those next 6 weeks. Whole arm was wrapped in medical gauze.

 

[Bobnova]

Ugh, that sucks
Hope it's all OK now!

 

[Arkade]

Is now. I'm gonna have to start the controller tomorrow. Was sick today. Hopefully All my parts are in. My Sayno looks nicer than the first one, and unlike most I've seen, has none of the balancing epoxy in the little indents on the impeller. Would that mean it is a perfectly balanced fan?

 

[Arkade]

Started testing my PWM Controller. Don't know if this is accurate, but at around 98% Duty cycle I get 16 Khz, but as i drop to 2 &, the frequency drops(you can see the wave form move) to the point I hit 8 Khz. Is this because I'm ussing NE556's?

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[Bobnova]

That's a larger spread than I got. Mine did 14k to 18k or something like that I think. Not really sure what would cause that large of a spread, dubious resistor or two maybe?
Some movement is a side effect of the design, the 0-100% version does away with it.

 

[Arkade]

Hmm, will this spread be an issue, i can't make the 100% Version because I already made PCB's. Just curious how bad it is. Will my Sayno get ticked off or not.

 

[Bobnova]

Doubt it. Only potential issue is noise. As far as accepting the signal goes I'd be very surprised if it didn't like it. Most of the fans I've tested that call for a 16kHz or 25kHz signal will run even down below 1kHz and above 30kHz.
Your mileage may vary of course, but I think you'll be fine. Might be worth checking the various resistors and diodes to make sure they're the proper value though. I'll dig my controller out tomorrow and re-measure the drift.


EDIT:
Couldn't wait, dug my old controller out and tested it. Something is badly wrong with my old controller, it does not behave in a logical manor. I'll have to build a new one on a breadboard to test. Whether I'll have time for that tomorrow or not I don't know. Right now I should have been asleep for an hour, so tonight is not the time

 

[Arkade]

So much Snow in my area right now. It's highly probable that it will move development to wensday. Way to much snow. Building will be closed tomorrow.

 

[Arkade]

Demetori left today, working on her machine , and she helped start the PWM Controller. I'll post pics when I get back, The machines here cannot read Raw Files from my Nikon. Kinda pissed though. Ordered 680 PF caps, 470 PF caps, 2,200 PF caps, POT's and some Diodes. They just sent me 20 680 PF caps. Thats it... good times.

 

[Arkade]

PICS!!!!!!!!!!!!!!!!!!

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Kinda pissed though. I Can't use this controller. It's frequency sweep problem causes huge amounts of noise. It's actually ear piercing. By any chance is this due to me using the NE556 instead of the TLC556?

 

[Bobnova]

Swap a different cap in, a smaller value will give you a higher frequency.
Functionally the 555 and 556 are identical.

 

[Arkade]

I asked about the "TLC" version VS the NE. and I am going to try lower value capacitors.

 

[Bobnova]

Oh, missed that. It shouldn't matter in theory, but I haven't tried one.

 

[Arkade]

Haven't tried a TLC or NE?

 

[Bobnova]

All of mine have been NE. The frequency sweep is there, but not big.
Here's a video I found of a three output all-NE556 controller I built:



The 0-100% 555-311-555 version:

 

[Arkade]

would have built the second one had I known the sweep would be this bad. D: already made my PCB's so yeah. Could it be the very cheap .01uF cap I used?

 

[Bobnova]

I really have no idea, I'd PM Bing and ask him if he's around. This end of electronics is not something I know a lot about.

 

[Arkade]

I'm going to assume by reading this thread(I've finally read the WHOLE THREAD) That the 556's i used are cheap 556's that need replacing, and that .01 uF cap needs to be swapped. Going to try 220pf caps as well to raise the freq to around 33khz to remove noise. hopefully this fixes my problems.

 

[Arkade]

Hey Bob, I found the problem. See the Pic showing the IC's, those are cheap crappy 556's. Went to radio-shack and picked up some LM556's and the sweep issue is gone. Now to take care of the noise with the denki i'm gonna put a 220 pf cap in it's channel. Debating if I Should ask Demetori for the 140mm Denki's to go with the machine. Then use that last channel

 

[Bobnova]

Ha, interesting. Also surprising.
Glad you found it!