[rickb]

I'm slightly disappointed to hear of your Gaugemaster experience.

I have been planning to take the plunge with DCC with a Digitrax Zephyr - I was a attracted to the jump inputs coz I don't want to buy a second throttle straightaway, but we want two-person control. I have a rheostatic controller - it may be old but it works well. This is presumably the sort of device Digitrax mean by a "smooth dc controller", but I haven't been able to find much about this on the 'net.

Does anyone know if the specs of the jump inputs are available somewhere?

Rick

 

[rickb]

Sorry for not understanding your reply. I can't think of a smoother smooth DC than you get with a rheostat - provided it's feeding from a smoothed power supply, of course.

Does anyone know what range of inputs is expected for the jump terminals? e.g. 0V to +/-12V, or 0mA to +/-200mA perhaps.

R.

 

[rickb]

Thanks for this. I took the top off my old H&M controller and worked out the way it's wired up. It has a 45ohm flat wirewound track and wiper, and also a concentric ring for reversing the direction of travel, depending on whether it's rotated clockwise or anti-clockwise. Simple and effective at feeding variable current to a loco motor.

What the Zephyr jump input needs (*) is a variable voltage, reversable in sign. Assuming the Zephyr full range is +/- 6V, then the old controller could possibly be used as a potentiometer, but only by wiring the 45ohms directly across 6V. This would be far from ideal because 130mA current would run through the wirewound track continuously. If I put a series resistor of perhaps 520 ohms, the current would fall more than tenfold - but so would the voltage.

So I'll have a think about wiring it via a simple amplifier consisting of a transistor or op amp, so that a more modest current flows through it but I can set the output voltage range. This isn't as easy as I'd hoped.

Maybe a simple potentiometer in a plastic box and with a reversing switch will have to do instead.

Rick

* PS I don't know the specs of the jump port yet (Digitrax haven't yet responded to my request for more info) but Tony's Trains has a useful article by Don Fiehmann: http://www.tonystrains.com/technews/zephyr-cab.htm
Don's article mentions the input impedance of about 1kohm and the input range of +/- 6V can be deduced from his circuit.