[GreenKeys] Loop supply, or are we still beating out wifes and kicking th...

[COURYHOUSE at aol.com]

ok here  we  go...
I see the links  etc!
 
Does the resistor need to be  so  large?  or  is that  just a large  photo ?
 
thanks !  ed#
 
 
In a message dated 5/25/2016 12:41:18 P.M. US Mountain Standard Time,  
rmowery28146 at earthlink.net writes:

 
I received a board in from Ebay that will convert about 10  volts to 30 
volts up to about 60 to 90 volts.  I was able to get about 95  volts out of the 
one I bought. 
It is almost like a DC transformer in that the higher the  input voltage 
the less current it will take to produce the same high voltage  out. 
Playing with it I inputed 12 volts at about ½ of an  amp.  The output was 
around 80 volts at 60 ma. Changing the input voltage  does not seem to change 
the output voltage if between 12 and 24 volts (the  limit of my test).   By 
using around 1080 ohms of resistance in  series and the USB to RTTY loop 
conveter that Eric just put out to drive the  Model 15 printer it works just 
fine.  I used some fixed resistors that I  had on hand and adjusted the 
voltage to about 80 volts for the 60 ma loop  current.  I then used about 1200 
ohms and adjusted to about 90 volts to  give me the  same 60 ma loop current.  
 
For someone that wants a very simple loop supply of a high  enough voltage 
this is a simple way to get it.  Just feed the board with  any voltage from 
about 11 volts up to 24 volts and you will get a constant  voltage you can 
adjust from about 60 to 90 volts.  Then Get any resistor  of about 1000 to 
1200 ohms , maybe less if you have several printers in  series,  and one of 
the wall warts from 12 to 24 volts at about half an  amp or more.   
Two words of warnings.  While it  is fed with 12  volts, be aware that it 
is putting out about 90 volts and enough current to be  like sticking your 
hand in the wall socket. If using a resistor like I show  below, make sure you 
cut the supply off and wait for the capacitors to bleed  off the charge.  I 
lit up a 60 watt 120 volt  bulb with mine just to  check it out.  
The other is the input and output is not totally  isolated and the negative 
leads are connected together. 
You will need a case to put the supply in as it does have  dangerous 
voltages in it. Not counting the case You should be able to put one  together for 
$ 15 to $ 20. If you need a meter to adjust the loop current you  can get 
one of the ‘free’ or $ 5 ones from Harbour Freight if there is one  near you 
. 
For those that do not have anything in the junk box or  cannot build much, 
you cannot  get any simpler than this. 
This is the one I used, it costs about $ 7 shipped from  China. 
_http://www.ebay.com/itm/191674539868?_trksid=p2060353.m2749.l2649&ssPageNam
e=STRK%3AMEBIDX%3AIT_ 
(http://www.ebay.com/itm/191674539868?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT)  
item  number: 
191674539868 
Use a resistor like this. 
_http://www.ebay.com/itm/152088667131?_trksid=p2060353.m1438.l2649&ssPageNam
e=STRK%3AMEBIDX%3AIT_ 
(http://www.ebay.com/itm/152088667131?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT)  



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