Re: [CAD_CAM_EDM_DRO] Power supply for Servos - Energy dump and such - UR...

wanliker@... wrote:

>In a message dated 2/19/2005 2:32:37 P.M. Mountain Standard Time,
>spadnos@... writes:
>
>one that shows when the circuit is
>"dumping" (across the load dump resistor, R7).
>
>What voltage would this be set for? the full power supply voltage, or just
>the expected raise in voltage from the feedback?
>
>

The current limiting resistor should be set for full power supply
voltage (since this circuit is supposed to prevent it form getting
significantly higher). The LED would only light when the FET is turned
on to dump power, since that chain is an open circuit with the FET off.

>Also a possible LED, across the main power supply voltage would show when
>the circuit is at full voltage, or when discharged below the critical LED firing
> voltage?
>
>

Actually, the LED across the +12V rail would do this. As long as the
voltage is above 12V, D4+R5 allow some current to flow. You might have
to change R5 though (decrease resistance, increase wattage) - it's only
set for 10mA in the present circuit, and you may want more to light an
LED brightly.

- Steve