We have been putting the recently bought RRampmeter to good use at the club, checking for DCC voltage levels at various points. We have found that in one power district, about 50 ft from the PM42 and with the DCS200 output set at HO, that we are getting 13.5 to 14.0 volts track voltage dependent on the number of loco’s operating in that power district or other districts, with momentary voltage fluctuations of 1/2 volt. In the other three power districts the voltage is closer to 14 volts with less fluctuations. We’re currently looking at how to improve the voltage in the poor power district. Our power bus is 14 AWG with Cinch Jones connectors between modules and barrier strip terminals mid-modules to which module track feeders are connected.
We’re puzzled that from time to time the RRampmeter red led lights up, indicating AC voltage present, at the same time as the green DCC LED is lit. We have no AC powered equipment connected to the layout modules, other than the 12 volt wall warts powering each UP5 panel, and the 110 volt AC utility bus running around the layout, which is about 12 inches away from the power bus and the loconet. We have yet to investigate further.
I am not familiar with the RRammeter but ohms law still applys. You have a higher than normal resistance somewhere. A power resistor across the rails at the furthest point will draw suficient current to detect a voltage drop in excess of “normal”. You can disconnect the DCC system and sub a DC power supply for this purpose if you wish. Are these “lower” voltages causing problems?
The answer is yes. I, and several other members have had locomotives studdering and slow down on this portion of track. The rails are CLEAN! The problem doesn’t seem to be the contact on the rails.
The first thing I would suspect is the Cinch-Jones connectors not making good contact because a wire is not properly soldered to one of them. Next, I would add more feeders from the bus wire to the track to compensate for possible loose or corroded rail joiners.
The solution might be 12 AWG wire and more feeders.
A simpler solution would be to run another bus in parallel (two 14AWG wires instead of one), which will halve the resistance of the bus. Plus a few more feeders.
As to the “AC” indicator coming on, the signal may be distorted enough that the meter thinks it sees a sine wave, not a square wave.
I would look for a loose or bad connector first. They are the weakest point in the system. 14 gauge wire should be more than enough to carry five amps for 100 feet (50 out and 50 back).
If you really get stuck, do run a parallel set of temporary feeders directly to the module for a test. If the problem disappears then you know that there is an excessively high resistance somewhere. It could be a bad solder joint, a loose screw on a terminal strip, a bad crimp or even a bad wire. Believe it or not I once wired a one room addition for a customer and found a bad taped splice INSIDE the outer jacket of the NM cable. It was done at the factory. [sigh] It’s a good thing that I checked it before the drywall went up.
Anyway, if the voltage lost changes from 5 volts to 2.5 volts with the parallel wire, then something is drawing a lot of current.