ok, here I go again.... I've been thinking about DC again. I have a DCC system , but I also think about my legacy stuff. Analog only mode: If I run DC with Atlas components. I just like Atlas components they remind me of my first layouts back in the 70's. I can also use atlas components to deal with my reverse loops issues. DCC only mode: If I connect my Zephyr to the layout and run with the atlas components in place. I can use the atlas components to control my Reverse loop area. DCC reverse loop: If I am running DCC and I have a reverse loop. I can enter my reverse loop block and stop my train. throw the switch on the reverse loop to have it running the opposite direction, then I reverse the direction on the engine before proceeding. The reason for reversing the engines direction as opposed to the track polarity is that swapping track polarity would affect everything on the layout making everything come to a crashing reverse halt. Is this correct? Do I misunderstand DCC? Do trains keep going the same direction regardless of track polarity with DCC? What is cheaper: Atlas stuff Toggle switches
You are misunderstanding DCC. You need to switch the polarity of the reversing section so that you don't get a short when the wheels cross into/out of the sections. The train won't change direction. You can change the polarity of the loop on the fly while the train is completely in the reversing section. Jeff
Jeff: A train entering a reverse loop changes direction when it leaves the reverse loop. Stay cool and run steam.......
Seems to me that you are changing polarity to prevent a short. In DC, you have to change the direction in addition to that. But in DCC, that direction signal would already be "in" the engine regardless of the polarity. DCC saves an extra step. Is that correct?
DCC makes the reverse loop change in polarity and direction a non-event. The train enters and leaves the reverse loop with no action taken by the operator. The reverse loop is wired to a reverse loop module that automatically changes the polarity as the train enters and leaves the loop. I have four reverse loops on the JJJ&E, plus a turntable. Each loop and turntable is wired to it's own reverse loop module. ( two wires in and two outside the loop). Stay cool and run steam.....
Ok now were getting somewhere. I think. You have to use stupid language to help me through this though. I understand the analog process it'svery basic DC stuff. DCC uses a reverse block, but the reversing is handled automatically? Most critical- If a train reverses it does not affect other trains on the main?
Your last question is right i think because the reverse loop is isolated from the rest of the track by having plastic rail joiners at both endsof the loop and on both tracks.
The thing to remember with DCC is that direction is controlled by the decoder itself. The power on the track is AC (at least for our purposes). The decoder rectifies the AC current (makes it DC) and sends the DC current to the motor to get the desired direction. Now to the reverse loop. If you are running a DCC decoder equipped locomotive and you change the polarity of the track, the locomotive doesn't care. It still rectifies the input current and send the the proper DC polarity current to the motor to get the desired direction. David
As you enter a reverse loop, if the polarity of the loop is different from the polarity of the main, a short will occur (same for DC and DCC). With DC, you need the polarities to match, but they must both be such that the train continues to move forward. While the train is in the loop, you must reverse the polarity OF THE MAIN so that it matches the polarity of the exit track of the loop, and the train continues. With DCC, the reverse controller (automatic or manual) changes the polarity OF THE LOOP(right under the train) to resolve any polarity mismatch as the train enters (or leaves) the loop. No polarity change for the main is required. As the direction of travel of a loco is determined by the decoder and NOT the polarity of the rails (the DCC signal on the rails is AC anyway), a change of polarity while the loco is in the loop has no affect on direction of travel and the loco justs keeps on boppin' along. JFM!
Just a note: The reversing section should be longer than the longest train to prevent two axles from crossing the gap between the main & the reversing section at the same time. You don't have this issue with a wye, since a train cannot enter and leave the reversing section at the same time. hth Michael
DCC makes the reverse loop change in polarity and direction a non-event. The train enters and leaves the reverse loop with no action taken by the operator. The reverse loop is wired to a reverse loop module that automatically changes the polarity as the train enters and leaves the loop. I have four reverse loops on the JJJ&E, plus a turntable. Each loop and turntable is wired to it's own reverse loop module. ( two wires in and two outside the loop). Stay cool and run steam..... </font>[/QUOTE]If you use an automatic reverse module the reverse loop is a non event in DCC. You can do it manually, in which case you change the polarity of the loop manually before you short upon entering or exiting the loop. The direction of the train never changes. This is what I thought I said before, but maybe not.... Jeff
Atlas stuff is cheaper, BUT, if you want to wire the layout for both DC and DCC, you will need toggle switches as well. You need to wire each block into a DPDT switch: one pair of wires goes to DCC another to DC. Conceivably you could still use Atlas stuff for the DC wiring section. You would have to gap both rails wherever you separate blocks. (I point this out because the Atlas stuff is set up for common-rail wiring, where you don't necessarily have to gap both rails.) You would still need a separate reversing switch or automatic system for the reverse loop in the DCC section of the wiring. (So you would have one reversing system when using DCC and another when using DC.) Concievably, you could use both at the same time, but it might get real confusing, and might not be safe for the locos if you made a mistake. This is only an issue if you have metal wheels on your rolling stock. To say the same thing differently: The reverse loop in DCC is ONLY a non-event if you install an automatic reverse module. Otherwise you HAVE to do it manually.
Atlas stuff is cheaper, BUT, if you want to wire the layout for both DC and DCC, you will need toggle switches as well. You need to wire each block into a DPDT switch: one pair of wires goes to DCC another to DC. Conceivably you could still use Atlas stuff for the DC wiring section. You would have to gap both rails wherever you separate blocks. (I point this out because the Atlas stuff is set up for common-rail wiring, where you don't necessarily have to gap both rails.) You would still need a separate reversing switch or automatic system for the reverse loop in the DCC section of the wiring. (So you would have one reversing system when using DCC and another when using DC.) Concievably, you could use both at the same time, but it might get real confusing, and might not be safe for the locos if you made a mistake. This is only an issue if you have metal wheels on your rolling stock. To say the same thing differently: The reverse loop in DCC is ONLY a non-event if you install an automatic reverse module. Otherwise you HAVE to do it manually. </font>[/QUOTE]Ok so assuming I only want to run an either or setup as opposed to mixed I just disconnect the power pack from one side of my selector and connect the DCC to it and flip all the blocks to the one setting and everything that was common rail is now DCC. So the Atlas can work under those circumstances. I am still confused by the DCC problem in terms of reverse loops. At some point the train will hit a opposite polarity of 180 degrees no matter how many block separate the tracks. Is the issue just that you have to make sure the engine does not short circuit the mainline ?
You are correct that at some point the train will come to a block boundary that is 180 degrees out of phase. When the wheels bridge the gap a short will occur. What an AR circuit does is to detect the short, and rather than opening the circuit like a circuit breaker would, it REVERSES the phase on one side of the gap (i.e., in the loop section) so that the short no longer exists. This happens very quickly, and in most cases the loco will not even hesitate. The Digitrax PM42 has four sections that can be configured either as a circuit breaker (open circuit on detecting a short), or an AR unit (flip polarity on detecting a short). This is accomplished via the connections to the relay contacts and the way the relay control circuitry is set to act. In your case where you want to switch between DC and DCC (but not both at the same time), you can keep the polarity of the loop constant and manually flip the polarity of the main just as you would for DC. It will work for DCC as well. Keep in mind though that an AR unit CANNOT be used for DC , as all that polarity flipping will cause the loco to do the cha-cha. (Or is that choo-choo?) Also, you SHOULD NOT use Atlas selectors, etc with DCC for a couple of reasons: 1) they aren't built to handle the DCC short circuit current and 2) you shouldn't use common rail wiring with DCC. Use "Direct Home" wiring, where BOTH rails are selected/switched.
You are correct that at some point the train will come to a block boundary that is 180 degrees out of phase. When the wheels bridge the gap a short will occur. What an AR circuit does is to detect the short, and rather than opening the circuit like a circuit breaker would, it REVERSES the phase on one side of the gap (i.e., in the loop section) so that the short no longer exists. This happens very quickly, and in most cases the loco will not even hesitate. The Digitrax PM42 has four sections that can be configured either as a circuit breaker (open circuit on detecting a short), or an AR unit (flip polarity on detecting a short). This is accomplished via the connections to the relay contacts and the way the relay control circuitry is set to act. In your case where you want to switch between DC and DCC (but not both at the same time), you can keep the polarity of the loop constant and manually flip the polarity of the main just as you would for DC. It will work for DCC as well. Keep in mind though that an AR unit CANNOT be used for DC , as all that polarity flipping will cause the loco to do the cha-cha. (Or is that choo-choo?) Also, you SHOULD NOT use Atlas selectors, etc with DCC for a couple of reasons: 1) they aren't built to handle the DCC short circuit current and 2) you shouldn't use common rail wiring with DCC. Use "Direct Home" wiring, where BOTH rails are selected/switched. </font>[/QUOTE]Thank you, that was very simple for my small geek brain to absorb.
