Re: Bleed resistor AND Led

Hi Jay,

Many of us like the little light and think it is neat to watch it get
dimmer over time.

As you by now have figured, the resistor is such a small fraction of
the power consumption, you lose next to nothing when left in the
curcuit. Beside, your LED will glow brightly when your power is on.

I power LED's near thier rated design of 20 mA to use a lower
resistor value and get a faster drain, and a brighter light at lower
voltages.

Some on this list want a fast dump and so use a 12 VDC PC style
pancake fan and run that puppy from the power supply. As it drains,
it gets quiet and that is your indication. of course you can do both.

Even others us the fan on a relay that switches from a seperate power
supply to the CAP's for power when the main power is shut off.
This is very simple, just use a double pole, double throw relay so
when the power is on, the relay is energized and the fan gets power
from your 'other' power supply, and when the main is off, the relay
de-energizes and it gets power from the CAP.

you can use a simple (cheap) doorbell transformer and a Diode to
power the fan from AC.

Of course, you can still use an LED to indicate power anyway.

for maximum brightness, figure a standard LED is 5 Volt, and consume
20mA. it will still light with much less current. Typically a RED
LED needs 1.7 volts to light.

At 20mA you are only pulling 0.02 amps so there is little effect when
you are under full power.

Have fun!

Dave

--- In CAD_CAM_EDM_DRO@y..., "jbolt001" <js3mc@a...> wrote:
> Sorry to rehash this againg but I'm not getting the whole picture.
My
> PS is 24VAC at the secondary so this should be 33.6VDC at the CAP.
> The CAP is 25000uF 50V.
>
> What size bleed resistor do I need and could someone show me the
math
> to figure this out. Can I connect the (-) side of the bleed
resistor
> to the gound side of the normaly closed contactor used for the
Gecko
> disable instead of across the cap or is this a bad idea? My
thinking
> is to only have the bleed resistor active when the power is off.
>
> For the LED across the CAP what size resistor do I put in series
and
> again the math to figure this out?
>
> Many Thanks,
>
> Jay