Need help with stir plate build

[sar_dog_1]

I am currently working on building a stir plate. I have a 12 volt power supply and a 12 volt .3 amp computer fan. I have a 10,000 om pot switch. The fan won't work until I turn the pots with all the way up . I read on another post that if I use a 50,000 home pot switch that may work to better control my speed. I have already epoxy the knob on to the pot switch and would rather not have to change out the switch but I will if I have to so I guess my question is which pots which should I use if I have to and is there anything else I can do to control my speed with my current setup. Thanks in advance and I know my fellow home brewers got my back on this one

 

[day_trippr]

Going from 10K to 50K would be totally the wrong direction given the symptoms.
You need a much lower resistance, and many folks have used a 25 ohm 3 watt pot with success. Radio Shack Part number 271-265...

Cheers!

 

[junior]

This is the easiest plate that I have found and did.

https://www.homebrewtalk.com/f11/building-stir-plate-check-out-usb-adjustable-computer-fan-253254/

 

[SpeedYellow]

+1 to the $12 USB fan. Works great and the speed control is super. If you have any questions at all about how to wire one up yourself, then you should put down the soldering iron and just drop the $12. Just my 2c.

 

[reed1911]

Are you sure you are turning the pot all the way up and not down? You should not need a pot at all if you have a 12v power supply and a 12v fan. I'd opt to measure the resistance you are actually using and work from there.

 

[Riot]

10k ohms is way too much resistance, there isn't nearly enough current to have any real control there. You need to either find a new pot, or accept a lower speed and reduce the output voltage accordingly. A 5V USB cable should get it spinning, but it's a pretty light vortex on anything bigger than a litre.

 

[BrewerDan1]

With a 12 v fan a 25 ohm pot is the way to go.

 

[sar_dog_1]

Thanks to brewer dan and day trippr!! I bought that pot and it works great. I sont have a flask or stir bae yet but a test with a coffee mug and a roll pin confirms it works.

Here is a pic of my stir plate. It is made from an old sound powered phone box off a ship. I put the pot inside the modified middle cover to act as a knob.

It was a blast making it. Thanks again for all the help!!