Strange problem with my DCC

[richhotrain]

Fosc

There is one thing I forgot to mention earlier, and it might be important: the problematic section is powered by an MRC booster (10A / 8A). This is isolated from the main control station, according to the manufacturer's instructions. Checking the connections of the two installed boosters, we found that they did not follow the trunk line layout. I refer to the data transmission line (Cable cat 6) between the control station and these two boosters [Note: the power supply itself of the line (bus) already followed the layout of the main line with the two interruptions due]. Well, by fixing the instruction links via the data cable mentioned earlier, I think the distressing problem has been solved

Had the OP mentioned two boosters at the outset, this thread would have gone in an entirely different direction. Glad that he got his problem solved.

Rich

[Fosc]

i'm asking if their "phases is different" How can we know this for sure, except by simple visual observation? Considering that my MRC system works with AC (rectified), using a multimeter is not enough to verify the phase. How to do this, please? I believe that both boosters are in phase with the base station.

[Fosc]

richhotrain

Fosc

There is one thing I forgot to mention earlier, and it might be important: the problematic section is powered by an MRC booster (10A / 8A). This is isolated from the main control station, according to the manufacturer's instructions. Checking the connections of the two installed boosters, we found that they did not follow the trunk line layout. I refer to the data transmission line (Cable cat 6) between the control station and these two boosters [Note: the power supply itself of the line (bus) already followed the layout of the main line with the two interruptions due]. Well, by fixing the instruction links via the data cable mentioned earlier, I think the distressing problem has been solved

Had the OP mentioned two boosters at the outset, this thread would have gone in an entirely different direction. Glad that he got his problem solved.

Rich

Yes, Rich, but I don't understand how not following the route with data cabling may have caused that disastrous problem.

[betamax]

Fosc

i'm asking if their "phases is different" How can we know this for sure, except by simple visual observation? Considering that my MRC system works with AC (rectified), using a multimeter is not enough to verify the phase. How to do this, please? I believe that both boosters are in phase with the base station.

 

I think you are confusing the power supply with the track voltage. Don't worry about the phasing of the AC input to your power supplies, it is irrelevant.

 

Phase in DCC refers to the state of the rails. If you measure across a gap in the rail, no voltage means things are in phase. If there is voltage, not just a few volts, one power/booster district is out of phase with the other.

 

A couple of volts would indicate there is a slight difference in voltages between the two rails. Something like 12VAC indicates an out of phase condition.

[richhotrain]

Fosc

 

richhotrain

Fosc

There is one thing I forgot to mention earlier, and it might be important: the problematic section is powered by an MRC booster (10A / 8A). This is isolated from the main control station, according to the manufacturer's instructions. Checking the connections of the two installed boosters, we found that they did not follow the trunk line layout. I refer to the data transmission line (Cable cat 6) between the control station and these two boosters [Note: the power supply itself of the line (bus) already followed the layout of the main line with the two interruptions due]. Well, by fixing the instruction links via the data cable mentioned earlier, I think the distressing problem has been solved

Had the OP mentioned two boosters at the outset, this thread would have gone in an entirely different direction. Glad that he got his problem solved.

Rich 

Yes, Rich, but I don't understand how not following the route with data cabling may have caused that disastrous problem.

Fosc, I am not blaming you for that initial omission. My only comment is that the thread might well have taken a different course.

[richhotrain]

betamax

I think you are confusing the power supply with the track voltage. Don't worry about the phasing of the AC input to your power supplies, it is irrelevant. 

Phase in DCC refers to the state of the rails. If you measure across a gap in the rail, no voltage means things are in phase. If there is voltage, not just a few volts, one power/booster district is out of phase with the other.

 

A couple of volts would indicate there is a slight difference in voltages between the two rails. Something like 12VAC indicates an out of phase condition. 

I agree. That is how I would determine if the rails on either side of the gaps are in phase.

Rich

[gregc]

Fosc

i'm asking if their "phases is different" How can we know this for sure, except by simple visual observation?

by measuring the voltage between the rails from different boosters across the gap

dcc polarity changes every ~50-100 usec.   a 1 usec phase difference is ~1-2%.   1% of 14V is ~0.14VAC

while this results in a short, i doubt it is long enough to trip a breaker.    however, i wonder if it is measureable and if it could cause the problems you describe.

as i said, it should be 0VAC

[betamax]

gregc

 

 

Fosc

i'm asking if their "phases is different" How can we know this for sure, except by simple visual observation?

 

 

by measuring the voltage between the rails from different boosters across the gap

dcc polarity changes every ~50-100 usec.   a 1 usec phase difference is ~1-2%.   1% of 14V is ~0.14VAC

while this results in a short, i doubt it is long enough to trip a breaker.    however, i wonder if it is measureable and if it could cause the problems you describe.

as i said, it should be 0VAC

 

Polarity is a term that belongs in the analog world and should stay there. In Digital Command Control there is no concept of polarity. DCC only has phase, meaning On or Off.

If you read a small voltage across a gap, that is a potential difference, not a phase difference, between the two districts. A large voltage means that one side of the gap is energized and other other is not, they are out of phase.

 

[rrinker]

 This still does not jive witht he reported issue. Having the phase wrong across power disctircs would cause a short when a loco crossed the gaps, not cause them to change direction. The phase of the DCC signal does not determine direction of travel (if it did, autoreversers couldn't work).

 Unknown if MRC calls for it, but most other systems call for a high capacity (same size as the main power bus) common wire between all boosters and the command station, because when there is a potential difference across gaps, this is where the current flows. Without a dedicated common, it tries to flow through the control bus cable, which is in almost all cases just thin telephone or network cable.  If the booster has an optoisolated input, then this doesn't matter.

 Also that mosnter MRC booster should not be connected directly to the rails in HO and smaller scales, 8 amps can melt a lot of plastic, and no HO train needs 8 amps. Splitting that up with circuit breakers makes better use of all that power, with less chance of a derailment melting you favorite loco. Of course, MRC doesn't sell circuit breakers, so they leave that out of their instructions.

                                                --Randy

 

[gregc]

betamax

Polarity is a term that belongs in the analog world and should stay there. In Digital Command Control there is no concept of polarity. DCC only has phase, meaning On or Off.

remember this is digital data modulating a voltage on the rails.  the digital data may be 1s and 0s, but the modulation is voltage polarity (analog world)

the S-9.1 DCC standard says polarity

The NMRA baseline digital command control signal consists of a stream of transitions between two equal voltage levels that have opposite polarity

i interpret polarity as you've reversed the wires

 

 

i don't believe the polarity is wrong.   i'm curious, repeat "curious", if there is a phase error which i believe is measurable as a small voltage difference.

if there is, repeat "if", i wonder if it could explain this problem.

Fosc

My locomotives AC 6000 BLI and J1 BLI, for the first time on that specific tunnel, unexpectedly stop and reverse

it seems to me the only way for the loco to stop and reverse is if commanded via DCC packet unless there's something specific to the decoder

a momentary ( < ~10s usec) could corrupt a DCC packet.   is it possible that it can repeatedly corrupt a packet such that it's interpreted as a reverse command?   (seems unlikely)

[Fosc]

Using a multimeter on the gap i measured:

stretch A - stretch B

13,1V - 12,9V

rail 1: 1,3V; rail 2: 1,8V

 

stretch B - stretch C

12,6V - 13,2V

rail 1: 1,0V; rail 2: 1,1V

[gregc]

seems like you are separately measuring the voltage between the rails and possibly ground.   don't understand why you said 13.1V - 12.9V.     i'm expecting a very small voltage.

but i now realize, that that voltage is unlikely to be zero since the boosters are at slightly different voltages.   i think the booster voltages would need to be adjusted to be as equal as possible at the gaps to make the measurement i've suggested.

considering this and the confusion about how to measure, i don't think there's any point in continuing.

[Fosc]

Gregc, 13.1 volts is the measure of the voltage supplied by the booster to the rail (branch "A") in the section just before the gap. And 12.9 volts is the voltage supplied by the main control station to the rail (branch "B") in the section just after the gap.Yes, the problem has already been solved casually, even though I could not understand the reason for the problem.My trace starts at branch "B", loops at the end and goes towards branch "C"; in this, it does another looping at the end of the "E" and goes straight to the "A" branch, where at the other end it does another looping and proceeds to amend itself in the "B" branch. The electrical installation follows this route (bus and all feeders). But the connections for data transmissions (cable cat 6) were before the random change: B - A- B -C.But thank you very much for your participation.