RE: [CAD_CAM_EDM_DRO] Re: Thought I had it figured out!!

I don't think a resistor is the way to go-you will need a BIG resistor to
limit the voltage to the motors, and it will get hot(nice in the winter if
you have an unheated shop, not so nice in the summer..:) )

If the Gecko instructions say you can use a voltage 5 volts above the servo
rating, and that's what you've got(30V servos, 25VAC supply->35VDC supply)
why not just do it?

Another option is to use a smaller transformer as an autotransformer with
it's secondary and primary connected in series in "buck" mode, on the 120VAC
side of your main transformer. This drops the 120VAC by the "buck"
transformer's secondary voltage. An 18VAC transformer used in this manner
would give you 102VAC in to your Main Tranformer primary winding, which
would lower your ouput voltage by a corresponding percentage(15% or 18/120),
and give you 21.25VAC out of the 25VAC secondary. This would give you
30.04VDC(give or take a few millivolts...:) ) voltage out of your supply.

a__ ___o___ ___b
UUUUU UU
Primary secondary

If the picture works; you connect your 120VAC to points "a" and "o"(the
primary) of the buck transformer.
Then connect one side of the secondary of the buck transformer to one side
of the primary(at point "o")
Then measure the voltage from "a" to "b". If this is BIGGER than the 120VAC
you are putting in at "a" and "o", then connect the OTHER side of the
secondary to the SAME side of the primary. Measure "a" to "b" voltage again;
it should now be "primary minus secondary" volts.
Leave the 120VAC across "a" and "o", and connect your main transformer
primary across "a" and "b".

Size the "buck" transformer to be able to handle the amount of current in
the 120VAC prmary of your main transformer(typically less current
required(hence a smaller transformer needed) than if you tried a bucking
arrangement on the secondary side of the main transformer).

Andy Wander
Verrex Corporation

-----Original Message-----
From: pug_harley_corvette [mailto:bsouthnow@...]
Sent: Thursday, June 23, 2005 6:49 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Thought I had it figured out!!

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Ed Fanta <atex57@m...> wrote:
Ed;
Thanks for the info. I'm going to use the 320's and I just read the
set up sheet that came with the shipment and it does state not to use
a power supply higher than 5 volts above the motor rating (duh). I
guess I should have figured out that the servo is nothing but a dc
motor with an encoder. But, I'm bein cautious. Don't want to
replace things right away. My transformwer has a 25 volt output
which will yield a 35 volt dc output. Is there a loading resistor
circuit I can go with to knock it down to 30. I don't want to
regulate the supply as it seems not the way to go! Thanks for all
the help.
billyjack>
Whoa there!! Steppers get the higher voltages not servos!! Servos
should