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Tag Archives: Joule Thief

Joule Thief (now with Pancakes)

Since this is the first post I’ll just cover a simple-yet-effective idea. The flat motors from floppy disc drives are commonly referred to as pancake motors (due to their shape). I’ve always wanted to do something with the stators from pancake motors, simply because I think they look fairly good, as components go.

These motors are very good for hacking. They normally have their own board that is mechanically separated from the rest of the drive which makes them highly accessible (I had to unscrew a sum total of 6 screws to get at each of mine – and three of those held the stator down). The boards themselves sometimes have motor drivers and position sensors (and so forth) that in this case are not used, but in other projects could be useful. Removing the coil from the board without breaking the wires is an exercise in patience and care. I find that applying gentle upward pressure and repeatedly heating each pad in turn is the most successful method. Remember that if one or two wires break, the situation can be recovered because we only need 2 sets of coils (the stator pictured has three sets).

Unilluminated Joule Thief

I used two of the three sets of coils to make the toroid component of a joule thief circuit. The LED is supported by its legs and extends out from the middle of the stator and points back on itself to illuminate. Since I am no electronics expert I work largely by trial and error, in these cases the resistor needed for the joule thief is typically ~ 0.1kohms but since it is so variable I suggest using a variable resistor (0 to 5kOhms will suffice) to work out where the resonance is, measuring the resistance and replacing it with a fixed resistor of approximately equal value.

In related news, the stators from DC β€œtoy” motors work very well electrically, however they look fairly rubbish because they are so hard to illuminate.

With pancake motors I think the effect is fairly good for a minimal outlay of components, effort and time. Also the flower/sun like resemblance is promising for decorations, jewellery etc. Versions of the Joule Thief circuit utilising motors present in small (CPU) fans and laptop CD drives would be ideal embellishments to clothing. Although there is not really much to working out which wire is which on the stator I will write an instructable detailing how to do it (in a short while). In the mean time, more pictures (Bear in mind that these pictures are taken at a long exposure in the dark, results may vary);

Update: I realise that the red version appears very different to the yellow version in the pictures, with the red seeming much more “hazy”. I believe that this is caused by the camera, both units looked pretty much the same by eye, and both photographs were taken using the same equipment. The pictures of the yellow version are a much more accurate representation of their actual appearance (Just imagine it in red πŸ˜› ).

Update: The instructable has been published. It is accessible at this address.

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