[GreenKeys] Loop supplies

[Ralph Mowery]

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.

 

I have played with a couple of just the voltage regulated supplies.  If you
need to measure the current, then a low cost ma meter or even one of the
'free' ones from harbor freight could be used.

 

Here are some of the ebay  links.

 

http://www.ebay.com/itm/191015464867?_trksid=p2060353.m1438.l2649
<http://www.ebay.com/itm/191015464867?_trksid=p2060353.m1438.l2649&ssPageNam
e=STRK%3AMEBIDX%3AIT> &ssPageName=STRK%3AMEBIDX%3AIT

 

http://www.ebay.com/itm/191015464867?_trksid=p2060353.m1438.l2649
<http://www.ebay.com/itm/191015464867?_trksid=p2060353.m1438.l2649&ssPageNam
e=STRK%3AMEBIDX%3AIT> &ssPageName=STRK%3AMEBIDX%3AIT

 

 

I would like to have a much higher voltage, but should be ok to run around
20 to 24 volts on a local loop.  You might even be able to get some of the
modules to boost the 5 to 12 volt supplies to 30 volts or so.  Sort of a
design waste, but  not very expensive either if you have some low voltage
wall warts.  Then all  you need is a plastic box to put them in and maybe
some phone jacks.  

 

I used a large empty pill bottle to put the computer to machine converter
board in.

 

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