Re: Power Supplies

Dave Shiels wrote:

>So let's say for argument sake, I am using Gecko 201,
>I have motors with a 3amp rating X 3 axis. that would be 9 amps

Just to clarify:

Since you mention the G201, you DO NOT need to use a bleed
resistor (as I've said a hundred times) as the G201 will bleed
the capacitor down for you (depending on the voltage, and size
of capacitor, in a minute or two)... In fact it is preferable NOT
to use a bleed resistor, because using one will bleed the capacitor
down to 0 volts and hence decrease the shelf-storage lifetime
(of an electrolytic) by up to 5 times or more (ie say 15 years down
to 3-4 years). Don't bother arguing with me, read the manufacturer's
specs, and also observe all BIG capacitors are shipped from the
manufacturer precharged to a volt or two (they don't do this just
for fun!).

However, using the G201 to bleed down the cap, the G201 bleeds it
down to about 1.4V and no further (automatically providing the
life-extending little bit of charge).

That being said, when you are initially testing the power supply,
without the Geckos hooked up, you SHOULD use a bleed resistor, to
make the capacitor safe for humans between wiring changes.

Lastly regarding the motors with the 3 amp (per coil) rating, if
those have 6 or 8 wires, that is the unipolar rating, and the 3 amp
per coil rating will change depending if you are wiring it to full-coil
(on a 6 wire), or parallel or series (on an 8 wire motor). Dave
Mucha is correct, add up all the maximum coil currents and multiply
by 2/3 (for your maximum amperage usage)... but most of the time
the power supply will be using less than this.

cheers
Doug Fortune
























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