[GreenKeys] Current loop not providing (enough) current

[Ralph Mowery]

The range finder (in simple terms) is to center the electrical pulses with the mechanics.  On a local loop it will not make too much difference if it is set from about 20 to 80.  To set it correctly you feed the machine with a string of RY characters at machine speed.  Move it toward one end to where the machine makes errors.  Note that number, then move it to the other end to errors start.  Note that number.  Take the 2 numbers and add them together.  Then divide by 2.  That is where the range finder should be set for best results.  Say you move to one end and it starts with errors at 20, then moving to the other end it makes errors at 90.  Add the two and get 110.  Divide by 2 and get 55 for the best position of the range finder for that machine.  That is assuming the RYs are sent perfect.  The reason for the RY is that all the selector fingers move in opposite directions.  It is possible to have a machine to do YR instead of RY and print perfect RY but not any other letter.  Found that out years ago when I was writing a computer program to send Baudot to a machine.

I think the picture shows the coils as 90 ohms each.  If so parallel they would be 45 (half of one coil resistance) and series 180 (double one coil resistance) ohms.    Parallel is where you hook both wires of each coil together.  Then to the loop.  That way the current goes through both coils at the same time.    Series is where you come into one coil wire, that wire goes to one of the other coil wires and then the other coil wire goes back out to the loop.  So the current goes in one coil , out of that coil, into the next coil, and then back to the loop. 

 Remember too that if you hook the wires up wrong the magnetic field will be week.  That is say in a parallel coil circuit you have a wire on the right and a wire on the left of each coil.  If you hook the 2 left wires together and the 2 right wires together they may or may not be correct and you will have to hook the right side wire to the left side wire if the field is weak.

You should measure the same current anywhere in the circuit.  That is you break the connection and then insert the current meter.  


Ralph ku4pt



-----Original Message-----
From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Zach Zarzycki
Sent: Friday, September 27, 2019 7:17 PM
To: GreenKeys
Subject: Re: [GreenKeys] Current loop not providing (enough) current


Got it! 

Reset the screw doohicky to the original position. Also I did not know about the range finder. It doesn't seem to make a difference where it is set, it was at 40 when I got the machine.


Right now the coils are one onto another and 1-3 measure 52mA and 2 and 4 also measure 52mA so assuming. 8mA is dropping somewhere between the power supply and the coils. I don't think this would be enough to put a kabosh on the whole thing but maybe? 

I could possibly lower my 2k resistor down to maybe 1.8k on the loop, and see if that pushes it up to 60 at the coil? Though, before doing that I'm going to take the PC board back out of the loop and see if maybe that makes a difference at the coils.

 Like I had shown in the once picture, I can see no other way I'm not great with series/parallel when it comes to coils, not sure why it's so hard for me to grasp but I'm 80% certain this is in series not parallel. 

Thank you everyone so far for your advice and encouragement, I'm sure I'll get this eventually, and I'm learning which is even better!