> > Hi all, perhaps someone can help with a wee power problem. I've
> > got a circuit board mounted on a motor shaft.

Could you mount a coil close to the motor rotor such that it picks up the magnetic field of a few Hertz from the slip? (Assuming an
induction motor).  Lots of turns and a bridge rectifier?


>A possibility
> > is to use a 7-segment LED (synched with the rotation) to indicate
> > the escapement movement

If you are only turning on the LEDs for an instant, at one particular angle of shaft rotation, then the average power will be very
low.

Use a PhotoLithium battery.

You could also presumably just count some revolutions between indications, if you don't need a reading very often (e.g. once per
second give the reading).

Or, use one LED, and change the length of time it's on for - you'll get a variable-length streak.

Or, flash a single LED from 1 to 10 times, starting at the known index of rotation, and then you can count the number dots it makes
visually.

Use 5 or 7 leds in an axial line and make the digits by forming them sequentially with rotation.  Using very high efficiency LEDs
may allow less current to be used than a 7-segment display, if the 7-segment display just has "ordinary" efficiency LEDs.

Use a Sony night-vision camera to allow you to have very dim LEDs and therefore low current requirements.

How about an LCD bar graph?

Ed Koffeman

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