Fan Back EMF

I did promise some measurements in an earlier thread

http://forums.majorgeeks.com/showthread.php?t=124541

I've been playing with an spare 12v fan and measured as follows, when spun with an air line.

Open Circuit

A cuspy waveform peaking to 18 volts one way 5 Volts the other

Terminated greater than 50 OHMS resistive

As open circuit

Terminated less than 50 ohms

Noticeable peak reduction to les than 1 volt by 10 ohms.

Impedance measurements at the motherboard terminals for the fan inconclusive due to supply line capacitors. I will have to do some soldering to attach flying leads to take measurements with the fan in place.

Studio T

 

Just keep in mind there is active circuitry in there. I rather enjoyed open one up, 6 coils (the magnet is in the blades), one IC, capacitor, and resistor. I've built many an RC oscillator, they are simple enough. The coils (and magnet) are where the action is. All you need is enough voltage to pop the IC, and you have junk instead of a component.

 

Just keep in mind there is active circuitry in there. I rather enjoyed opening one up, 6 coils (the magnets are in the blades), one IC, capacitor, and resistor. I've built many an RC oscillator, they are simple enough. The coils (and magnet) are where the action is. All you need is enough voltage to pop the IC, and you have junk instead of a component.

Canned air is enough to do it too.

I made the discovery working on test equipment, blowing dust bunnys out of it.

 

Opps, sorry.