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Old 11-30-2012, 11:27 PM   #61
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Default I need my fan to go slower

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?

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Old 12-01-2012, 05:49 AM   #62
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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.

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Originally Posted by Jackjama View Post
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.
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Old 12-01-2012, 12:33 PM   #63
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Thanks i will finish building before i do anything.

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Old 12-03-2012, 01:56 AM   #64
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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

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Old 12-04-2012, 12:37 PM   #65
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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?

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Old 12-05-2012, 02:54 AM   #66
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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.

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Old 12-06-2012, 08:00 PM   #67
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These are avaiable for $10 shipped on ebay:

http://www.ebay.com/itm/12V-40V-10A-Pulse-Width-Modulation-PWM-DC-Motor-Speed-Control-Switch-Governor-/120949408302?pt=LH_DefaultDomain_0&hash=item1c2925 822e

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

img_1942.jpg
improved-stirplate_pic-1.jpg

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Old 03-28-2013, 05:51 AM   #68
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how would you go about adding a power supply to this project?

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Old 04-11-2013, 02:59 AM   #69
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well, heres my take on it so far...


Let me know what you think
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Old 04-02-2014, 05:11 PM   #70
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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?

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