[GreenKeys] Loop supply options

[Ralph Mowery]

Describing the loop is somewhat difficult .

When in the space condition there is no current or voltage across the
printer circuit.  If using a 15 printer type, the instant the loop goes to
mark there will be almost full voltage across the magnets.  Then for the
next few milliseconds it decays to somewhere around 10 or so volts and the
resistor will have the major part of the voltage dropped across it.  With
inductance of the coils in the circuit, it takes a short period (few
milliseconds) to reach a steady state.  When the circuit is open  (space) it
takes another few milliseconds for the collapsing field of the magnets to
quit producing voltage. 

Some of the newer machines have an internal loop supply so much of that does
not apply to the external loop.

Ralph ku4pt


-----Original Message-----
From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Steve Garrison
Sent: Monday, September 09, 2019 1:19 PM
To: jim.w2jc at gmail.com; greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] Loop supply options

I would guess it kind of along the same lines as which way does the current
flow.   In the SPACE condition the loop is open and there is nothing across
the magnet, no current to measure and no voltage present.  Like turning the
circuit breaker off that controls your wall out. No voltage present so you
shouldn't find out with a shock that you forgot to turn the breaker off.

But I do get your point, almost all of the voltage is dropped at the big
resistors but the current is the same through out the loop.

Steve G./N4TTY


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