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Subject: Re: Reducing contact resistance for low volt use?
Date: Sat, 14 Dec 2002 12:15:19 -0800
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John Muchow wrote:
> I did find one unit on ebay:
Can't tell much about it. You may be able to look
it up on the vendor site.
> 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?
It would be hard to find a big power supply that
didn't have current limiting.
> The odds of getting a schematic for surplus supplies like these must
> be pretty low (if the company is not around anymore, that is).
You are correct. Some reverse engineering will be
required. The current limit
is likely there to prevent damage, not to supply
Even if there's an adjustment, it likely won't go
anywhere near zero.
And there may be stability problems trying to get
it that low...all depends
on how they did it. Analog supply will be easier
to manage than a switcher.
One option is to set the big supply up for 10A to
100A. Use a smaller power
supply for mostof your testing. Drag out the big
one only when you need the
> 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
> is...easily determined.
By the end of the day at swapmeets, they're free.
Just plug it in to make sure
it works. I once got one set fot 230V. Thought
I'd just rejumper the primary.
Oops! No jumpers. Oh well, was free.
> >>>As for the brass brush connection, watch out for
> >>>the resistance/heat.
> >>>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
> >>>battery case.
> >>>Learned very early that I needed more current for
> >>>shorter time to prevent this.
> >>>A hot contact area under pressure can bend
> >>>significantly inward.
> More good tips, more thanks. :-)
> John Muchow
Bunch of stuff For Sale and Wanted at the link
Spot welding head, Tek 2465, TFT projector, ham
radio, 30pS pulser
Tektronix Concept Books...
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