On Wed, 24 Nov 2004 07:23:46 GMT, the renowned Gunner
wrote:
Ok...Im way way out of practice on my basic electronics...blush
I found a 12vt dc diaphragm pump of the same type thats in the tig
coolant unit I was given. (Lincoln Magnum)
The old pump and all the gizmos were fed 24vt ac. I did find a tiny
full wave rectifier inside the pump, which apparently only had bad
brushes. Unfortunately..I didnt get all the parts to the motor, else
Id simply stick in a new set of brushes and voila.......sigh
The new pump is 12vdc at 7 amps. The rectifier is no biggie.
What is the best way to drop the 24vac down to 12v?
Dropping resistor? Ok....blush..what value and wattage do I use?
(sounds of derisive laughter in the backround...sigh)
DC-DC converter? Ok..where and how much?
Thanks...
Gunner
Well, I havn't tried this but I think it should work...
The cheapest way would be to hack an old (free) microwave oven
transformer. Angle-grind the welds that are holding the E and I lams
together. Cut off the high voltage winding and discard. Remove the
magnetic shunt between primary and secondary and discard. You might be
able to salvage the wire from the primary side (if not, use some
slightly fatter wire than in the original primary).
If so, unwind it carefully (there should be about 120 turns), counting
the turns, and put 1/3 the number back (about 40). That's your 24VAC
primary. Replace the high voltage winding with 1/6 the original turns
on the primary (about 20 turns). That's your 12VAC secondary winding
to go to the bridge rectifier. Tack the wlams back.
Here's what a typical microwave ovent transformer looks like:
http://www.zbr.co.jp/e_catalog/e_catalog_10.pdf
Note the E-I lams are not interleaved, so it's easy to get the core
apart.
Here's a suitable bridge rectifier:
http://semi.shindengen.co.jp/en/d20xb80.pdf
20A/800V available from Mouser for $1.46 ea. qty. 1. P/N: 627-D20XB80
plus a few bucks for UPS ground.
Best regards,
Spehro Pefhany
--
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