PLCProf posted:With the Z-4000 set to 20 volts at no load, how many amps does it take to pull it down to 16 volts?
As noted, the train only draws a couple of amps, so it's not a high load issue.
Don
GGG posted:A easier method,, though it should have been done when upgraded is to go with modular TMCC upgrade. You could have used a Engine Mother board with R2LC and an ACDR for the Pre War Motor. You can let AC Track Power directly into the ACDR which is just a H Bridge Triac circuit for controlling the motor.
You could have than used a small device to take the High AC input and regulate it down to a constant 16-18VAC and send this to the R2lC mother board. Since the ACDR and the Mother Board only have a PWM DC Connection between them this would keep Voltage in the right range for the TMCC components. The ACDR can handle a Higher AC Voltage. G
Thanks, George. If the Arduino circuit idea from JGL proves unsuccessful for any reason, your idea here would be the best bet. The cost and work of swapping is not extreme. Don
JohnGaltLine posted:I like the bi-directional diode idea better than either of the ones that I came up with, actually, as far as dead simple goes. Just keep in mind you are going to need some really big diodes. The benefit of using the load bank would be that it could be made responsive to the change in voltage at the transformer to keep output at exactly 18V (or whatever) where as the diodes would drop in .6 volt steps, or in the simplest form a 2 volt or so jump.
As for how to read the transformer voltage, I would use a knock-off arduino micro-controller as the brains of the operation. I'll work out some details for you, if you like as I have time over the weekend, but the basic setup would be to rectify the voltage to DC, then use a voltage divider to bring the transformer's maximum power output down under 5 volts. this will give you a zero to 5 VDC voltage from your 0-24VAC transformer output. This signal voltage can then be read by the Arduino, which, in turn can be programed to turn on a relay at a set voltage to turn on the diodes, or turn on a varying, pulse-width modulated signal to a set of big power transistors on a load bank or triacs on the line to the track. If I went with the diode method, I think I would at least use a few relays to let the system have a few steps, clicking on more and more diodes in series as the voltage rises.
JGL
I've been intrigued by the Arduino stuff at my electronics store for a couple of years, so it would be fun to use that as the method here. Need to learn about those devices and associated software anyway. Note I already have suitable 10 amp, 50 PIV diodes on hand so that's not a barrier. Dividing the drop into 0.7v increments by bringing one silicon diode pair in at a time would certainly add precision, so output to track would always be either 19.3 or 20v unless Z4000 primary output gets below 19.3v. That should be OK, because the train behaves well down to track voltage of 18v or so. That could solve some other higher load passenger trains' concerns when a max distance from feed, too. I use a K-Line voltmeter boxcar to see what's what "way out there", and even with my 14 and 12 ga wiring the voltage at the train can drop to 14v or even a tad less with the Z4000 set at 18v. If the Arduino-diodes-relays approach is tied to a differential in voltage from baseline (is it?) then it could let me make the "usual" voltage for all other trains 19v, and keep the output to track at 18.3-19v. That would add a few volts at all times, especially the critical times when the train is most distant.
BTW I had a large basement loop years ago using ZW power, and a heavy train like two 2343 "growler" F3s with 4 motors, plus 9 lighted aluminum passenger cars drawing 8-10 amps, would drop the most distant voltage down by 1-1.5v, and that was with 12 ga copper wire in a continuous bus, with soldered drops every 6 feet or so for both sides of the GarGraves rail circuit, so that current had 2 paths to the train 50 feet away, and still there was this much drop. Even giant wire doesn't mean "no voltage drop!" If you calculate the resistance per foot for your wire from reference tables, then calculate total resistance using wire gauge's ohms/foot and distance, that is about how it comes out, as well.
Thanks for your help with this! Should be fun figuring out how to make it work.
Don
