pulse width modulator kit?
 

One question, does anyone have any experience/ideas about using this kit for fan speed control?
http://www.allelectronics.com/cgi-bi...804&type=store

That should work for fans.

If the fans starts behaving erratically, then add a cap at the circuit output.

Try this instead
 

http://www.radioshack.com/product.as...Fid=990%2D0200

$6. Details of its assembly and usage here:

http://benchtest.com/rack_fan.html

Thanks for the replys. I'll look at the RS kit.

I looked at this kit, and the circuit is the same (or nearly so) as a prototype I did. It should work just fine. Much cheaper than the kit I got a year ago!

If it is the same, it uses a 556 (two 555's in a chip) to send out a variable width PWM signal to a MOSFET which supplies the PWM 12VDC to the fan.

I'm using speedfan presently, but my next cooling adventure will have two 26v (12volted) 172mm Comair fans on a big Modine oil cooler, so the fans may be quiet at 12v. The All Electronics pwm kit may handle the power better than the Radio Shack kit.

If your fans draw about one amp, you might simply replace the given power MOSFET with a beefier one. The MOSFET that Radio Shack is using is probably the IRF510 (276-2072) which is capable of handling 4 amps of continuous current. That means that it should handle two fans with continuous current draw of 2 amps. Don't worry about the current surge when the fans start up. The typical MOSFET's are capable of handling current spikes several times their limit for continuous load (16 amps in the case of the IRF510).

The IRF510 is $1.99 at RadioShack (order it by part number if they don't have it in local stock).

If you go to a real electronics store, you can get power MOSFET's capable of handling much larger loads. For example, browse Mouser Electronics at this page to see the N-channel MOSFET's. Take a look at the bottom. See the IRF510 part? Mouser sells it for $0.63 instead of $1.99. Same part. If you need more current, use IRF520 (which sells for $0.86) which can handle 9.2 amps of current.

Good info, thanks. I'll so a search for pwm theory/circuits and modify a kit or use a design that can be found. A pot in series with two fans would be less work, but not nearly as interesting. I don't have the fans yet, but they may have a fan stall sensor which may be used to shut down the system. This might be a good project, a pwm control/multiple fail-safe board.

I've done some of that research already. Take a look at this ProCooling article. There are some good links to more detailed information there too. I like to give credit to sites and books that helped me.

Thanks for your input; I'll breadboard the circuit and give a try.

i made a few extras thermal feedback PWM controls a while back & still need to get rid of a them (fan(s) speed up as temperature increases). they feature 4A max, pro-MFGed PCB, a 10 LED bargraph duty cycle display, fan ON switch, tested reliability, & hi-gain adjustment to suit any needs (water coolers usually need high gain, & i designed them for my h2o rig--0-100% within a ~3C change). sell 4 $35+S&H, invested well over $70 each, not including the hours i put in designing this unique circuit. let me know if you're interested.

edit: BTW, i have a schem if you want to try & build it yourself.

Yes such a setup is NOT cheap to build; $35 is a reasonable price :)

Got pics?

I'll take a schem! PM or e-mail it to me?

Yeah! A schematic would be great! Share your engineering!

I'd like a schematic as well. :)


If you could give a few more details/pics I might even buy one of the pre made ones.