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June 10, 2014 at 2:19 am #22957
I live in Phoenix and as summer is approaching the OSRPi v1.3 in my sealed case is getting pretty hot. With heatsinks it is already running over 85c for a short amount of time. Was wondering what the best way to install a small exhaust fan. Am I able to splice one of the 5v rails from the RPi and run a small fan?
Something like this fan: http://www.amazon.com/gp/product/B0076O831G/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A2H3QE25AGJEMY
Thanks!!June 12, 2014 at 2:18 am #27135
Anyone? It’s getting hotter.
Should I go with a 5v and splice? Should I go with a 24v and splice before OSPi? Or maybe a USB fan if I can fit one?June 12, 2014 at 3:49 am #27136
You could get a 24vac one, attach it to one of the solenoid relays and write some code to turn it on when it gets hot?June 17, 2014 at 3:48 pm #27137
The 5V fan you linked to seems to draw 400mA of current. If you use it, I would recommend using a separate 5V power supply, instead of drawing power directly from the OSPi board.June 23, 2014 at 4:55 pm #27138
You could get a 24vac one, attach it to one of the solenoid relays and write some code to turn it on when it gets hot?
I love this idea – I’m not sure there are 24VAC fans but being able to control it based on temp or a schedule or whatever would make sense.June 24, 2014 at 12:38 am #27139
Remember that the OSPi’s power supply is 24 Volts AC. It derives it’s power and the power for the Raspberry Pi from this base supply. Most irrigation transformers provide about 1 – 1.25 Amps AC which is sufficient to run the electronics and switch two sprinkler valves (Master and one channel). Most fans for electronics use are designed to run from a DC supply. The DC for the electronics is provided by a LM2596 chip which, why adequately powerful to provide enough power, has been implemented on the board specifically to provide a fairly small amount of DC power.
There is no heat sink on the LM2596 so heat generation is a consideration. Further the electrical noise generated by many fans may cause problems for the Pi. Given this and the limited overall power available “within the box” I would recommend that any extra fans are powered by their own, separate power supply.
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