[GreenKeys] Constant current selector magnet loop controller

[Bob Camp]

Hi

The MJE340 constant current circuit goes back at least into the early 1970’s
as far as common use goes (= that’s when I started using it). As with any 
loop, the first question is going to be series magnets or parallel magnets (20 or
60 ma loop). I’m guessing that anybody looking at low voltage already has 
gone to a parallel magnet setup. 

Next question is - how many printers (or punches or …) do you want to put
on the same loop? The simple (but not quite perfect) math is that the voltage
doubles each time you add another printer. 

To answer the question - you can run two or three printers and get acceptable
copy on a 90V / 60 ma loop. 

Bob

> On Feb 10, 2017, at 11:08 PM, Jim Haynes <jhhaynes at earthlink.net> wrote:
> 
> 
> By using a transistor in a constant-current connection it is possible
> to get good loop signals with a lower supply voltage than the standard
> 120V 2000 ohm circuit.  Has anyone worked out what supply voltage is
> sufficient with a constant-current circuit?
> 
> It's all probably irrelevant because what we get out of ITTY or some
> other local sources are perfect signals, unaffected by the properties
> of a long transmission line, so we don't have to accomodate some of
> the things that matter in wire-line service.
> 
> But what prompted me to originate this message is an article in the
> February 2017 issue of Electric Radio about using a part for constant
> current reforming of electrolytic capacitors.  The part is
> IXYS IXCP10M90S available from Mouser and others, and is described
> as a switchable current regulator.  I haven't had time yet to study
> the data sheet, but looks like this gives a constant-current circuit
> just by choice of one external resistor.  And it's good for a supply
> voltage up to 900V and an output current of up to 300ma.  One thing
> I don't see mentioned is how fast it responds to being turned on and
> off.
> 
> Has anyone on the list played with a device like this?
> 
> Jim W6JVE
> 
> 
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