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WA2ISE > TECH     03.04.21 23:41l 12 Lines 1121 Bytes #999 (0) @ WW
BID : 21075_AL0Y
Read: GUEST
Subj: High voltage (~200VDC) bench supply with shut-off bleeder
Path: IW8PGT<IZ3LSV<I3XTY<I0OJJ<GB7CIP<CT7AXA<CT1EBQ<W0ARP<AL0Y
Sent: 210403/2236Z 21075@AL0Y.#NNJ.NJ.USA.NOAM LinBPQ6.0.21

As many of us, I built a high voltage (160V or so, 300ma) bench power supply.  One hazard is when it is lightly or no loaded, its filter caps will keep a high voltage charge for a good long time.  I figured a good way to reduce this hazard is to have a bleeder resistor cut in when turning the supply off.  I just needed a double pole double throw toggle switch (to replace the single throw single pole I used before).  One pole does the powerline, and the other pole will connect the bleeder resistor to the high voltage output when the switch is thrown to "power off".  I used a power resistor of about 2500 ohms 10W as the bleeder.  This discharges the caps in about 10 seconds.  Yes, the caps are fairly big.  120VAC secondary to a cap, then a choke, and another cap. 

Having the bleeder not connected while power is on cuts current waste, until I need it when I turn it off. 

                -------------------- transformer primary
powerline---o  o  o nc
         ON         OFF   switch terminals
         nc o  o  o----resistor------B  supply output
               |
            ground      nc= no connection



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