What switch do I need to enable/disable fan with wind speed measurement by a DIY anemometer?
simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Anemometer wind detection circuit.

Assuming your anemometer can put out a few volts the circuit of Figure 1 should work.


12 V relay, RLY1, will provide power from the battery to the motor.
When the anemometer puts out some voltage it will turn on Q1 which will turn on Q2 which will energise the relay.
When the relay is energised the contact will change over and the motor will be disconnected from the battery.


You need a relay to match the battery voltage. The contacts should be rated >= to your load current. Your local auto shop should have something suitable.

Check the anemometer polarity in the wind before connecting up. Tip: you could test the device and cut-in speed by driving around with the anemometer on the roof of your car.



Edit after motor specified:





Figure 2. Motor (generator) specification from Mabuchi Motor.

I didn't watch the video but at 3 V it will spin at about 2500 RPM. This means that to generate 3 V you will have to spin it at 2900 RPM. This is close to 50 revs/second and seems most unlikely for an anemometer. If it ever happened then Burning Man is over.

You need to come up with a different wind detector.