[vcf-midatlantic] A little electronics hack
djg at pdp8online.com
Mon Sep 30 08:43:25 EDT 2019
> >> It's called a 'crowbar' circuit. Prevents things from burning up.
What I normally called a crowbar circuit is the overvoltage protection
where it intentionally shorts the output of the power supply. This sounds
more like over current protection.
> What are common reasons why those stop working? Neville and I didn't see
> any obvious signs of damage to it.
Either component value shift or failed component. You indicated that it is
driving the motors better than it ever has. It may also be your motors
are a heavier load than it was intended to drive.
If you're interested in investigating further if you point us to schematics
we can give suggestions.
> On Sun, Sep 29, 2019, 1:56 PM Mike Loewen <mloewen at cpumagic.scol.pa.us>
> > On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
> > > Neville noticed something that I wouldn't have. The circuitry contains a
> > > safety mechanism to shut off all power if the current jumps too high,
> > such
> > > as a kid inserting a paper clip. There's probably a technical name for
> > that
> > > but I do not know it. Anyway, for unknown reasons this circuit was
> > kicking
> > > in! He jumped it with an equal-length wire. :)
> > It's called a 'crowbar' circuit. Prevents things from burning up.
> > Mike Loewen mloewen at cpumagic.scol.pa.us
> > Old Technology http://q7.neurotica.com/Oldtech/
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