Skipper Billy Posted October 8, 2020 Share Posted October 8, 2020 I want to install a couple of 80mm computer cooling fans in my observatory to run 24/7 to extract air and provide a sustained throughput of airflow. I have a 12v DC supply handy.All the ones I can find are either three wire or four wire.Rather than try to figure out by trial and error (and possibly damaging the fans) which wire does what I thought I would ask the collective wisdom if its even possible to run a three wire fan with just pos and neg 12v supply ???Something like this... https://www.amazon.co.uk/dp/B0119SLG18/ref=emc_b_5_t 1 Quote Link to comment Share on other sites More sharing options...
Skipper Billy Posted October 8, 2020 Author Share Posted October 8, 2020 Ooops posted in wrong section - mods can you move it please to DIY Astronomy - sorry!! Quote Link to comment Share on other sites More sharing options...
Alex Posted October 8, 2020 Share Posted October 8, 2020 Yes :-) Easiest option is to go for 3 pin and just use the + and -ve pins. The other pin a feed back of the fans actual speed, used by a speed controller. I installed a PC fan on the back of my 200PDS with a PC fan speed controller and works a treat Quote Link to comment Share on other sites More sharing options...
Gina Posted October 11, 2020 Share Posted October 11, 2020 Posted by: @AstroOlly There should be a red and black wire in the group of 4, they are your pos and neg.... ?StewYes, that's what I do. 1 Quote Link to comment Share on other sites More sharing options...
KevS Posted October 11, 2020 Share Posted October 11, 2020 I have a similar system on the greenhouse, I run the extract fan slower than the input fan.The very marginal increase in air pressure, that is probably only a few millibar has a noticeable effect on the volume of greenfly. Dependent upon how well sealed the obsy is, it may keep help the midges out. Quote Link to comment Share on other sites More sharing options...
Bas Posted October 11, 2020 Share Posted October 11, 2020 I have one in my shed powered by a cheap solar cell. And that works pretty well. Quote Link to comment Share on other sites More sharing options...
Skipper Billy Posted October 11, 2020 Author Share Posted October 11, 2020 The fans have arrived - with black, green, white and yellow wires !! I will assume black is -ve but any ideas on which might be +ve ?? Quote Link to comment Share on other sites More sharing options...
Skipper Billy Posted October 11, 2020 Author Share Posted October 11, 2020 @7170 You're a star - many thanks. Will try it tomorrow - I am on the outside of a very nice bottle Merlot just now! 1 Quote Link to comment Share on other sites More sharing options...
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