261Views3Replies

# Transformers, how do they work? Answered

Im trying to make my cheap laptop cooling stand use stand alone power. ie, not using the USB power. i obviously cant wire up that little fan motor to standard 120v. SO, i have this transformer here, i pulled it out of an electric razor. It makes sense that i could use this in my fan project. it has six, now de-soldered, pins, three on each side. how would i wire up the neg and pos of the power supply and the fan to this part?

PS. due to my webcam, it make the images blurry. the serial is:
4222 018 47541
SA-0101
If that helps any

Tags:

## 3 Replies

Jack A Lopez (author)2012-07-05

A transformer converts an AC signal into another AC signal at a different voltage level.  For example a transformer like the one you've got there might take 120 VAC on its primary side, and give 6 VAC on its secondary side, so that the ratio of the magnitude of the voltage on the primary side, to that on the secondary side is 20:1.

I claim that this ratio of input AC voltage, to output AC voltage, is a property of the transformer, and it is also the ratio of the number of turns on the primary, to the number of turns on the secondary.  If you actually want to know how and why this works, the Wikipedia article on transformers might be a good place to start:
http://en.wikipedia.org/wiki/Transformer

Regarding this plan to drive a fan with your transformer:  you did not mention the kind of fan you are using, but if you pulled it out of an old computer, it probably wants DC, not higher than about 12 VDC.

Because the fan wants DC, you will need some kind of rectifier circuit, to change the low voltage AC from your transformer, to DC.  In fact the board on the electric razor, from which you removed the transformer, probably has such a rectifier circuit, consisting of maybe 2 or 4 diodes, plus a big electrolytic capacitor.  This section of the Wikipedia article on rectifiers,
http://en.wikipedia.org/wiki/Rectifier#Full-wave_rectification
shows two of the usual circuits used for converting AC from a transformer into DC.  The rectifier circuit your razor used was probably either the one using 4 diodes in a "bridge" shape, or the one using 2 diodes connected to a center-tapped transformer, if your transformer has a center-tapped secondary.

rickharris (author)2012-07-04

steveastrouk (author)2012-07-03

It would be better to just find an old router power supply brick and use that. The codes on the transformer don't help.