Science Buddies: "Ask an Expert"

Use a Fan to Generate Electricity- I bought the lowest voltage LED that Radio Shack had.....2.3v and used a drill to spin the fan, thinking the drill will spin it much faster than my finger and still couldn't get it to light, I've double checked that the LED is good, and even tried it with a small christmas bulb to see if that would light no luck. Does this project actually work? Do some fans not generate voltage in reverse? Has Anyone else gotten this to work? What type of fan did they use? What voltage LED?
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Tammi Farnsworth

TAMMI FARNSWORTH wrote:Use a Fan to Generate Electricity- I bought the lowest voltage LED that Radio Shack had.....2.3v and used a drill to spin the fan, thinking the drill will spin it much faster than my finger and still couldn't get it to light, I've double checked that the LED is good, and even tried it with a small christmas bulb to see if that would light no luck. Does this project actually work? Do some fans not generate voltage in reverse? Has Anyone else gotten this to work? What type of fan did they use? What voltage LED?
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Tammi Farnsworth

Okay, I've found a better site for the battery driven LED. Look at:
http://www.instructables.com/id/EQHAVI0QJ6EV2Z9SKP/


Use this to test that the LED is good, and to make sure you know what the negative and positive ends are. If everything works, then we will try the next steps.

I found out you can't use any household fan, you need to use a DC fan such a fan from a computer power supply, and you still need to get it spinning pretty fast for good results.

TAMMI FARNSWORTH wrote:I found out you can't use any household fan, you need to use a DC fan such a fan from a computer power supply, and you still need to get it spinning pretty fast for good results.

A DC fan does work, however, my understanding of the project was that the AC fan would work, you would just see it dim when you had the wrong polarity. Glad you had sucess, and I'll try to get the project page corrected.


Louise

This is yet another Science Buddy project in the Electricity and Magnitism area that has issues in the materials called for.

There are several types of AC motors; however, most of the ones in common use do not have any permanent magnets in them and will not function as generators. Most household and industrial AC fan motors are brushless induction type which use alternating electrical current to produce one magnetic field and induce another field in an armature (rotating part) winding. For single phase induction motors, a phase shift starting circuit usually consisting of a capacitor and speed cut out switch is used so that the magnetic phase (North-South magnetic pole) angles differ slightly so that they start in the desired direction.