Re: [CAD_CAM_EDM_DRO] EDM wire tensioning

On Thursday 06 April 2006 07:04 pm, Paul Kelly wrote:

> A micro generating a PWM signal for your winder motor based on some input
> would be easy (if you're a micro kind of electronics guy) it'd save you
> half a bridge.

You don't need a micro to do PWM, though it can be easier that way. A simple
astable multivibrator (can be done with a couple of transistors or a single
chip) is good enough.

> Philips make some good power op amps, up to about 25W I think. As for
> sensors. The homebrew options that spring to mind are:
>
> A wedge shaped paddle that moves in front of an LDR, angle of wedge
> determines rate of change of the value of the LDR.
>
> Hall effect, something like a UGN3503 and a weak magnet on the tensioning
> arm.
>
> I'm told that there are some proxes that have a linear output..
>
> All this is being on the assumption that you cant use a potentiometer as
> the pivot for the tensioning arm?

> > Suggestions appreciated. I even wondered about an optical
> > approach with an LED in a tube getting closer or further from
> > a sensor.

I'd think that a shutter moving from side to side would be a much better
choice. I used to work on home and church organs, and some used such a
setup in their expression pedals...

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