[ARC5] Power Supplies for Your ARC-5

[J. Forster]

It may be that there is just a very short, high current spike that trips the
overcurrent protection on your particular supply and dynamotor. It does not work for
me. In the No 19 MK III the dynamotor spins up only when it's switched to transmit
and does so in less than a second. This requires a pretty beefy supply. A battery
works very nicely.

BTW, there was another post suggesting putting a number of supplies in series. If you
are going to do that, you should shunt each and every supply with a high current
diode, so that if one of the supplies goes into a current limit condition, the others
cannot reverse it's output polarity and cause damage to the limiting supply.

Good luck,
-Johh


David Stinson wrote:

> I'm sure that's correct.  All I know is if I hang 200,000 ufds on the output of the
> supply I was using, the dyno starts fine.  If I don't, the supply shuts down.
> 73 Dave S.
>
> "J. Forster" wrote:
> >
> > David Stinson wrote:
> >
> > > The current ratings written on the dynamotors are the running currents.  The
> > > starting surge current will be much higher.  I don't remember off hand what
> > > the starting current for a DM-33 or DY-8 is, but I think it's around 25 amps.
> > > Most of these supplies have protection against surges.
> >
> > > You can overcome this by using some large capacitors in a bank to provide the
> > > surge current, while the power supply
> > > provides the running current.  24 volts in batteries will also work.
> >
> > It will take a MIGHTY capacitor bank to start a dynamotor. Simply put:
> >
> > Q (charge) = I (current) x T (time)
> >
> > Q = C (capacitance) x V (Voltage)
> >
> > therefore I*T = Q = C*V
> >
> > in this case, the V is the allowable voltage drop during startup. Putting in
> > reasonable numbers:
> >
> > I =25 amps, T=1 sec, V=(28-23volts)=5
> >
> > 25 * 1 = C * 5;  solving C = 5.............. FARADS, ie 5,000,000 microfarads.
> >
> > That's a pretty big capacitor.
> >
> > Think about floating batteres.. That's what I use for my No 19 MK III set, and
> > it works just fine. Marine batteries in a fiberglass case are ideal.
> >
> > Good luck,
> > -John
> >
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>  then by my own conscience."
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