[WannaMakeStuff]

Hi all,

I am in the final stages of designing my CNC control 'box'.

I want to incorporate a method of draining the charge in the capacitors when the unit is turned off.

I have searched this forum for ideas and most posts discuss using appropriate value resistors connected through a DPDT main switch to drain the charge (when the main switch is in the off position).

Some suggest the alternative of wiring the cooling fan to operate when the switch is off - exhausting the capacitor and allowing you to hear the fan slow and stop.

I like the idea of using the charge to give a last burst of cooling to the electronics - but my question is this;

What if I use some 12v incandescent panel indicator lamps (3 or 4 in series for my planned 40 volt power supply) connected in parallel with the fan to add a visual check?

[wantsout]

I put a 1/2 watt resistor across the capacitors them selfs and it seems to work fine. its about 3000 ohms and it takes about 1/2 minute to drain,the supply is 65 volts. will try the neon bulbs on mine....

[martinw]

Dear WannaMakeStuff,

Thank-you. Give us some more information if you can.

I have no idea how large your PSU electrolytic capacitors are, the normal operating voltage, and which "current draining stuff "you still have connected down-stream of the PSU when you turn off the PSU, before you put in some extra bleed circuit. It could be that a bleed circuit is not needed.

BTW, I am not trying to be awkward...

Best wishes,

Martin

[Mariss Freimanis]

No need for a bleeder once the drives are attached. Nothing bleeds a cap quicker than a drive consuming current to power a motor.:-)

Mariss

[wantsout]

I have 6 each 8200uf in parallel in mine and i will take out the bleeder resistor when i hook up the drives to the motors, but for now Ill leave it so i wont get zapped.. I hate that when that happens...