[GreenKeys] Loop supplies

[Ralph Mowery]

I did just order a couple of the boards from China so should know something
in a few weeks.  The boards are suppose to have an adjustment for the
current along with the voltage so an external resistor will not be needed as
if it was just a voltage board.  It may not even work at all, but thought it
may be worth a try for about $ 10.  

It was also mentioned in another post about using such a low voltage supply.
I know about the dv/dt (rise time) of the current, but if fed by almost
perfect waves from the converter it may stand a chance of working
,especially if the teletype uses the lower inductance of the holding coils.
I would like to have close to 100 volts or more, but did not see any modules
that would put out that kind of voltage and regulate the current for a few
dollars.  I will have to look around and see if there are any.

De Ralph ku4pt


-----Original Message-----
From: epvgk at limpoc.com [mailto:epvgk at limpoc.com] 
Sent: Tuesday, May 17, 2016 7:49 PM
To: Ralph Mowery
Cc: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] Loop supplies

On Tue, May 17, 2016 at 07:18:01PM -0400, Ralph Mowery wrote:
> While I have not tried them, ebay has some modules from China that 
> might just work for a local loop.  Buy one of the modules which is 
> just a circuit board and look around for a 24 volt wall wart DC 
> supply.  The modules are only about $ 2 to $ 6.  Some of them can be 
> adjusted for a constant current and should be able to put out about 20
volts for the 60 ma loop.
> 
>  

You should be able to use one of those with my CL adapter board, but you'll
need a small current limiting resistor as the board already puts 187 ohms
total in series with the loop. (plus the dc resistance of the selector
magnet coils, etc)

eric

>