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Topic: Powering fan from Arduino (Read 845 times) previous topic - next topic


I want to power 5V 0.8W 2wires fan from 5V Arduino pin, but i dont want it to draw all 160mA - how can I decrease fan power so it takes smaller mA's ?


You have an 'internal' resistance of 31.25 ohms that is the fan winding. If you put a 100 ohm resistor in series with the fan, you have 131.25 ohms of resistance. That will allow 38 milliamps in your circuit. The 5 volts will be split with 3.8 volts across the resistor and 1.2 volts across the motor winding. Approximately .19 watts. Now whether that fan will start/spin with that resistor in series is a guess. Try a 33 ohm resistor as a second choice and see if that allows the motor to run. 

Remember, the 5 volts will remain at 5 volts, the motor's internal resistance will remain constant. You are varying the current by adding resistance (and therefore lowering the power). Less power = slower speed.

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