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From: jmuchow@SPAMMENOTcamlight.com (John Muchow)
Subject: Re: Reducing contact resistance for low volt use?
Date: Fri, 13 Dec 2002 22:45:11 GMT
Organization: MindSpring Enterprises
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X-Server-Date: 13 Dec 2002 22:45:04 GMT
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>>>There are a whole bunch of practical issues
>>>building something in a box that can be carried
>>>off the bench and hooked up with real wires.
Yea, I'm just beginning to realize all that's involved for this
>>>Here's what I suggest.
>>>[snipped great list of things that really
>>>helped me to understand what's going on]
>>>Having 5V to burn dramatically simplifies the
>>>You can use wires that you can flex by hand. But
>>>remember, that doesn't relax the requirement for a
>>>low resistance contact point. You don't want heat at the contact.
>>>And you don't have to build any active circuitry
>>>or worry about heat sinks.
Very cool, and you explained it well enough that even with my
ignorance, I understand what's going on. I just need to find a power
supply with "full-scale" current limiting that I can access (unless
they all can be adjusted from zero up to their rated current value).
I did find one unit on ebay:
But I can't tell if it has current limiting...or is this something I
can assume is available on all power supplies of this size/wattage?
The odds of getting a schematic for surplus supplies like these must
be pretty low (if the company is not around anymore, that is).
A couple of surplus houses on the Web advertise pulled LH Research
supplies for about $20 each...damn good deal. If they're tested, that
>>>As for the brass brush connection, watch out for
>>>To get reliable contact, the bristles need to
>>>contact at an angle so each has it's own springiness/compliance.
>>>Copper is not good for this cause it's too ductile.
Good tip, thanks.
>>>I'd worry about too much pressure with current
>>>In my welding experiments, I've blown holes in the
>>>Learned very early that I needed more current for
>>>shorter time to prevent this.
>>>A hot contact area under pressure can bend
More good tips, more thanks. :-)
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