Detailed step-by-step stirplate speed control

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hexmonkey

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For those of you considering building a stirplate with the advanced speed control circuit, as described in this thread:

https://www.homebrewtalk.com/f11/my-homebrew-stirplate-8850/index3.html

I found a site that has a terrific step-by-step of how to create that speed control circuit:

LM317 Voltage Regulator

I just built one of these last night, (before I found the link) and coincidentally, this is almost exactly how I did it, down to the way the components are arranged on the board! :mug:
 
Now I can get started on this as well. I had purchased most of the parts several months ago but was at a loss as to haw to start building the circuit. It's been a looong time since I have done any of this stuff and I no longer have any of my old electronics manuals anymore. Thanks for the heads up on this great resource!
 
quick question about the lm317. If I use it with a 12V transformer thats delivering 17v on my meter and between 300 and 500ma would I need to add an additional heat sink to the lm317? I tested it for 30 minutes on a breadboard without and additional heat sink and the top of the lm317 reached 80°F while running the fan with 4.5V. Just wasn't sure wheather it would get hotter than that over the course of 36-48 hours of continues operation.
 
Ideally this circuit would be supplied with 14V instead of 12V because the LM317 will drop a couple of volts, at least. They can dissipate quite a bit of heat on their own so I don't know how necessary a heat sink is - especially with a fan blowing!

Another idea is to use a 12V LED dimmer. These use PWM rather than linear control and can be bought for less than $5.
 
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