[GreenKeys] Inexpensive loop supply

[COURYHOUSE at aol.com]

I do not  see a  photo at this  link  Help?   send  direct to me  please  
thanks  Ed#  
 
 
In a message dated 6/9/2016 11:14:01 A.M. US Mountain Standard Time,  
rmowery28146 at earthlink.net writes:

Just to  show how inexpensive you can put together a loop supply and
interface it to  Erics USB board for those that do not have much to work
with.

The  parts are simple.

Wall wart that will put out from about 11 to 20 volts  at over .75 amp ( 750
ma).

Resistor of about 1200 ohms and 10 to 20  watts for a 90 volt supply board.
Somewhat higher if a higher voltage is  used. I used an adjustable one that
was rated about 2000
Ohms and set it  for about 1200 ohms.  Not too critical as I used the  
voltage
adjustment to set the 
Current to exactly 60 ma. That gave a  voltage of about 90 volts from the
board.

Boost converter off ebay  from China. There are several boards that can be
used.
The one I used is  rated for about 45 to 95 volts. The input voltage is not
critical as  
Long as it is between the minimum and maximum values.  If you change  the
input voltage, the 
Output voltage will not change.  Ebay item  number 191674539868.
There is another that others may want to use that is  rated for about 50 to
390 volts.
They are less than $ 10 shipped.   Be careful of the boards.  While they
operate off low voltage  DC
They will light up a 120 volt 60 watt light bulb.

The connector  between the resistor and loop wiring is a Wago lever nut part
number  222-413. 
They are about $ 15 for 50.  They make good connections  between different
size
wires and can be used over and over. Not really  needed, but put in for a
demonstration.
The resistor could be soldered  to, but for those without a way to solder,
the screws work.

I did  cheat and use a Molex connector on the loop connection and some Power
Poles  on the 
Wall wart, but you do not have to. 

I used an old aluminum  box to put it in. The resistor and boost board will
get warm so  
ventilate the box. The board from Eric was put in a plastic pill  bottle.
You may be able to see the hole where the push button can be  pressed if
needed.

If you do not have a meter to set the current,  the 'free' one at Harbor
Freight will work.

I do have a reasonable  well equipped shop, but thought it would be fun to
see how inexpensive  
this could be done.

Here is a link to the finished  supply.


https://drive.google.com/drive/folders/0B7wJcih38lRAM2dwRm1aNW9CSWM

Ralph
KU4PT






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