Date: Sun, 12 May 2002 21:43:34 -0400

Author: Dick Heckathorn

Subject: RE: Power Supply


Having a rather strong horseshoe magnet, I can use a hand-crank gencon
connected to block u-shaped wire that will swing like a pendulum. When
current goes though it, I get a 7 to 8 inch amplitude. I fasten paper to
the vertical wires so it can be seen to the back of the classroom. The
gencon is much less than $300.


By the way, my first u-shaped wire was made of steel. Needless to say, I
then made one out of brass.


"Science is nothing more than learning how to communicate with nature in
such a manner that it will talk back."

Helping teachers who facilitate, motivating students who learn.
Dick Heckathorn 14665 Pawnee Trail Middleburg Hts, OH 44130
Physics Teacher CVCA 4687 Wyoga Rd Cuyahoga Falls, OH 44224
330-929-0575 VM 120

-----Original Message-----
[] On Behalf Of David Kardelis
Sent: Thursday, May 09, 2002 7:51 PM
To: ''
Subject: RE: Power Supply

I bought a 40 Amp 0 -20 VDC power supply from MCM electronics. Works
for magnetic force on wires etc. It was relatively cheap $300 bucks.


David Kardelis 451 E 400
Chairman, Dept of Chemistry and Physics Price, UT 84501
College of Eastern Utah
435-613-4201 (fax)

-----Original Message-----
From: Urs Lauterburg []
Sent: Monday, May 06, 2002 2:40 PM
Subject: Re: Power Supply


This is quite a lot of amps you are looking for and even a 25A rated
autotransformer will not be cheap and certainly huge and heavy. Even a
regular transformer for 25A is going to be bulky. You are aiming at a
power supply and of course you can get them, but they will not be cheap.
Another option is to make one yourself but then again the components
add up as well. The best deal I am sure is, if you can find such a beast
surplus from an old research lab. I have been able to get my hands at a
100A power supply, a very exotic and heavy piece of equipment but
useful specially to show various B-fields of different current

Talking about Boise, I wish you all a good meeting and a very pleasant
in Idaho. I would love to come, but then again the trip to the US will
to expensive for our public funding. A year has past since the last
in Rochester and a lot of things have happened. I very much enjoyed my
first attendance to an AAPT meeting and to meet many of you nice
instructional resourcers.

My best to you all, have a good time and take good care of yourself

Best regards


Urs Lauterburg
Physics demonstrator
LabVIEW wireworker
Dept. of physics
University of Bern

>I would like to buy a 25 volt 25 amp variable DC power supply.
>It should simply consist of an on-off switch, a high current variac,
>a high current bridge, and a filter capacitor.
>Does anyone know where to get a variable DC supply this simple?
>Most power supplies have lower power and a lot more regulation.
>I don't mind having the ripple on the DC. I want 625 Watts power and
>Mcmaster-Carr has manual battery chargers that are similar to this.
>But they do not have a variac so they're not variable, and they don't
>a cap so they produce pulsating DC.
>Does anyone know where to get one like I described?
>Can't wait for Boise!
>Gerald Zani e-mail:
>Manager of Demonstrations phone: (401) 863-3964
>Department of Physics FAX: (401) 863-2024
>Brown University Providence, RI 02912-1843 USA
>Do a little more of that work which you have confessed to be good,
>Which you feel that society and your most Just Judge rightly demand of
>Cultivate the tree which you have found to bear fruit in your soil.
>If you have any experiments you would like to try, try them.
>Now's your chance.
>Henry David Thoreau, Journal entry, 1850.