Hey everyone,
I am trying to replace my old DC auto reverse relay for my new layout. On my old one, I had a bit of isolated track with a reverse relay board attached with isolated connectors etc. I used it on my old layout flawlessly as it was super easy to install, program and run. However, now I am wanting to use a DCC engine on that line and the only thing I find when I search is autoloops. I had a bit of track running alongside then under the main line and it went out of sight where it would slow, stop, wait 15 seconds then come back. I don't need an autoloop for that do I?
I am running a Digitrax system and when I Google what I am looking for, it always comes back as an auto loop. I just want the train to run out of the sceen then came back. It's a doodlebug... back n forth.
Thanks!
George
Ok... I think I just answered my own silly question. A friend sent me a link to Tom's Trains and the Digitrax BXPA1.
do you understand that track polarity is constantly reversing in DCC because that is how commands are communicated to the decoders? reversing track polarity does not cause a DCC loco to change direction
but the even in DCC, track polarity needs to be reversed, such as in reversing sections to prevent shorts. that's what a DCC autoreverser, such as the Digitrax BXPA1 is for.
slowing, stopping and reversing the direction of a DCC loco requires sending it commands and knowing the loco's DCC address
greg - Philadelphia & Reading / Reading
gregcbut even in DCC, track polarity needs to be reversed, such as in reversing sections to prevent shorts.
While not any more 'correct', I think I'd use "phase" rather than "polarity" to explain why the same method of wiring up a reversing loop is needed for DCC as for DC.
i believe polarity is appropriate and the correct term. phase involves timing and i don't see how it is any clearer.
perhaps i would have been more correct in saying the voltage polarity (+/-) is changing constantly
if the power from the two booster terminals going to the track are labeled A and B, connecting A to B causes a short. that's why even in DCC, the connections to the track, which rail is A, need to be reversed at the ends of a reversing section, the same as in DC.
i agree i'm used polarity to describe both the track connections as well as the instantaneous track voltage
I’m confused, if you don’t have a reverse loop why do you have or want a reverser?Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
RR_Mel I’m confused, if you don’t have a reverse loop why do you have or want a reverser?
I’m confused, if you don’t have a reverse loop why do you have or want a reverser?
I suspect the OP is looking for a "ping pong" circuit. This simply reverses the polarity of the power on a DC track, so the locomotive reverses direction and goes back.
Something like this does not exist in DCC. The nature of the DCC signal is really not conducive to this kind of circuit. Somebody had a circuit that would do this and more, Tam Valley perhaps, but it proved kind of unreliable and the product eventually disappeared.
It takes an iron man to play with a toy iron horse.
deckroid Hey everyone, I am trying to replace my old DC auto reverse relay for my new layout. On my old one, I had a bit of isolated track with a reverse relay board attached with isolated connectors etc. I used it on my old layout flawlessly as it was super easy to install, program and run. However, now I am wanting to use a DCC engine on that line and the only thing I find when I search is autoloops. I had a bit of track running alongside then under the main line and it went out of sight where it would slow, stop, wait 15 seconds then come back. I don't need an autoloop for that do I? I am running a Digitrax system and when I Google what I am looking for, it always comes back as an auto loop. I just want the train to run out of the sceen then came back. It's a doodlebug... back n forth. Thanks! George
I can think of three relatively easy ways to accomplish this:
1) Most DCC locos run just fine on DC, so you might be able to just run it as is. The thing to be comcerned about, however, is what kind of output the reverser has. Since you said that it slows and then stops, there is a good chance the reverser has a PWM (pulse width modulated) ouput to control the speed, and DCC decoders do not like PWM DC controllers. It still could be run this way by adding capacitors to the output to filter the PWM signal.
2) You said you have Digitrax. If you happen to have a Digitrax Zephyr, you could have the output of the reverser feed one of the Zephyr's jump ports with that jump port configured to control the train you are wanting to run back and forth. You could still have issues if the reverser output is PWM. If so, it might be fine depending on what kind of filtering Digitrax has on those ports, otherwise you would have to add additional filtering.
3) DCC Shuttle with Station Stop SDCC1
CSX RobertI can think of three relatively easy ways to accomplish this:
Make that five:
4) DSS1 LocoShuttle
5) Motorman CKT-PINGPONG
Phase is the correct term for DCC, as it describes the relationship between the rails. There is no polarity, as at any point in time one of the rails is in one of two states: On or Off. The other rail will always be in the opposite (inverted) state.
The outputs of the booster are, being digital, the source and sink. Each output is changing between source and sink, controlled by the signal from the command station.
In a reverse loop, when the phases don't match at the exit you will get a short. The incorrectly named "auto reverser" flips the phasing so everything matches. Some European companies accurately call it "automatic inversion", because it inverts the relationship.
DCC isn't hard to understand, the problems occur when attempts are made to force a digital technology to fit an analog model.
There is another way: Automatic Brake Control (ABC), which uses Asymmetric DCC.
Some decoders, such as the Loksound DCC, can be configured to stop, then reverse direction, using ABC Shuttle Train Control and two ABC modules.
betamaxPhase is the correct term for DCC, as it describes the relationship between the rails.
i disagree. i would say "phase" describes the instantaneous voltage between the rails (i.e. + or -) with respect to time. and the phase is continually changing, for example, it is NOT simply reversing every 100 usec.
the image below illustrates a phase differences between two signals that is not simply 180 deg (a DCC reverser cannot correct this)
of course there is polarity because there is a short if you bridge the A rail to the B rail. almost all electrical signals are carried by two wires that can be connected in one of two ways
a DCC reverser simply reverses/flips/inverts the A/B connections between the booster to the track using either a relay or mosfet switches. It does nothing more than a simple reversing switch
A DCC reverser doesn't delay/shift the signal, changing it's phase relationship with the signal coming from the booster. a DCC reverser doesn't measure the phase, it simply detects a short
a decoder monitors the phase of the signal and measures the time between phase changes. that time represents a 1 or 0.
396
deckroid Ok... I think I just answered my own silly question. A friend sent me a link to Tom's Trains and the Digitrax BXPA1.
Rich
Alton Junction
richhotrain deckroid Ok... I think I just answered my own silly question. A friend sent me a link to Tom's Trains and the Digitrax BXPA1. Looks like the OP solved his own problem. Rich
Looks like the OP solved his own problem.
No, the BXPA1 won't do what he wants. I gave some solutions above.
Hello All,
"Firsts we need to 'define' the word 'definition'!" !!!
When most people refer to an "Auto Reversing Unit" in DCC, they are typically referring to a circuit that senses a "short" and reverses the polarity of the new section to match that of the incoming section, then upon exit, matches the polarity of the next section.
These are typically found in loops, wyes, and cross-over sections in ovals and dogbone-type pikes.
It took me a few readthroughs of your posts to understand you want a point-to-point reverser- -back and forth on the same track.
deckroidMaybe the easiest is just to run the chipped Budd to run DC.
In your situation, I believe this might be the simplest solution.
As long as this DC track is completely separate; both physically and electronically, you should have no problems. Just set and forget.
If you are trying to incorporate this back-and-forth function into your overall DCC pike this will require some form of isolation, detection, automation, and expense.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
The more I dwell on this, the more I wonder if we're overthinking it.
All he has to do is set up a trip at each end that cuts power to the motor leads, reverses them, and powers on again. Nothing in the DCC or the decoder changes, and all the controls still work including the manual speed, stop, and reverse controls if he wants them.
I'm tempted to note that it's an RDC so he has room for a whopping mother of a keepalive, not that he really needs that big a one... here wired to the decoder's 'higher functions' to keep it going while the motor is interrupted or even if track voltage is interrupted to give an extended timed delay...