DIY Stir Plate Issue

[jzamora3]

Hi guys,

I'm building a stir plate and having an issue where the potentiometer doesn't slow down the speed. Its either on at full-speed or nothing at all. I'm not much of an electronic guru so I'll try and explain in details as much as I can.

80mm Pc Computer
100oHm Potentionmeter (Linear)
12V DC Power Adapter
Rocker Switch

Ground Wire -> Black Wire on Fan
Power->Rocker In, then Rocker Out->Middle Post on Pot
#1(0r #3, I've tried both post on Pot)-> power (red) on Fan

Any idea what's going on? This doesn't work too good because it goes from 0-100 and instantly throws the stir bar. There's an image attached if that helps.

Thanks for any advice!!

 

[MoonBrewer]

Edit: Hard to tell from the pic but you may want to swap wires on the pot: white to 12v, Red to fan power, black to Gnd. Fan wires: black to Gnd and Red to middle pin on the potentiometer. That will vary the fan voltage from 0 to 12.

Not sure if 100 ohm pot is appropriate for your setup. Typically a voltage regulator or PWM is used to control the fan voltage. Lots of build threads with schematics if you search the forum or Google

This thread https://www.homebrewtalk.com/showthread.php?t=630105 discusses several options.

 

[FunkedOut]

How many amps does the fan draw?
Is it a 12V fan?

 

[MoonBrewer]

Here's a diagram showing what you want to do with just a potentiometer. 100 ohms may be too low as you will be burning 120mA through the potentiometer, check to see if it gets too warm in normal operation.

 

[jzamora3]

It's a 12V Fan.

MoonBrewer - Thanks!!! That fixed my issues!