Re: [CAD_CAM_EDM_DRO] Chopper max voltage?

> The 2A driver boards use a 7805 to provide the 5 volts for the logic
> section of the circuit. This would get awfully hot and burn up if you tried
> to use 36VDC for the input to the 7805. That was the only reason that I
> recommend keeping the supply voltage down to 18VDC
> You can go up to 36VDC for the motor supplies but I would recommend
> providing a separate source for the +5 logic.

Or you can put a power resistor in series with the supply line to the
7805. Size it so that the voltage into the 7805 under maximum load is
comfortably above the regulator drop out. This was standard practice
at one place I used to work, only we dropped it after it was pointed
out that if the regulator shorted out the resistor might possibly draw
enough current to get dangerously hot, but not enough to blow the
fuse.

So use at your own risk (but really I would guess it would be fine in
a hobby application, even though questionable in a consumer product).

Chris

--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
http://www.mdc.net/~stratton
(617) 629-9830 home (temporary), 253-2606 MIT