I am looking for a DCC unit (or circuit) that can be used in the command line between the DCC command unit and DCC booster. It needs to stop the transmission of DCC signals that have a significant DC component (DC locomotive speed) and pass all other DCC signals.
Modern decoders can sense if they are being fed DC or DCC current at the rails. To make them insensitive, and therefore unresponding, to DC current, with the resultant occasional dash-to-doom when one powers up the rails, alter the setting of CV 29. It should have a value of 34. The value 38 is for the same running qualities, but able to switch automatically between the two forms of current, depending on what it finds upon power-up.
Thank you for the very useful information. I am in the process of setting up a CV programming capability. For the time being, I want my locomotives to keep their DCC/DC capability without changing this CV. I am in the process of checking out the setup of an added DCC service district on a short section of test track. When I hit the stop button on the controller, it caused an immediate full speed runaway in the layout district! I am also able to repeat it. I no longer trust this controller (or any other DCC controller) to never send such a signal to the layout booster.
What booster are you using in the problem district? Most DCC boosters are supposed to shutdown the output with the absence of a DCC signal.
Thank you! I am afraid if a name the booster, this post would get side track, and lose site of the original question. It is the type of booster a newbie like me would buy. The booster (according to my understanding) is acting as designed. It amplifies what it gets and sends it out (works with both DCC & DC signals). It handles shorts, but that is about it.
Thank you! The control unit is new. In all fairness to the manufacture of the control unit, I am using it in non-standard way for test purposes on a test track. But what I have seen has convinced me that: “I no longer trust this controller (or any other DCC controller) to never send such a signal to the layout booster.” It would have been better if I would have said “(or any other DCC controller of this type)”. With this type the phase of the power to track is aligned at installation. Apparently there are not a lot of users using this type of controller, so I am unlikely to find the “DC blocker” circuit that I am looking for.
Thank you! I agree with you statement. But I am also confused and do not understand this response in the context of this post.
Runaways are not uncommon with multiple booster DCC layouts. Generally it is a timing issue. The command station's signal doesn't stabilize before a secondary booster powers up. No DCC packets in the DCC signal, decoder sees it as DC and takes off. That's why most if not all decoder manufacturers include the option of turning off analog conversion in CV29. Simply turning the command station on a few seconds before switching boosters help keep the unstable signal from being boosted to track power levels. Turn the command station off last. Martin Myers
Thanks for the great information. I wish it fit my current situation. “When I hit the stop button on the controller, it caused an immediate full speed runaway in the layout district! I am also able to repeat it.” This is on very simple test track with two districts and one locomotive, which I was (fortunately) able to quickly grab. The controller showed a “fault” and appeared to be in some kind of fault-recovery mode. I have a NCE packet analyzer that will be used to trap what is happening on the controller output. I have not used this analyzer before and am waiting on a power supply for it. I won’t to minimize the times and time I need to have my controller in this apparently confused mode. I prefer to provide the results and details to the appropriate manufacture first, and give them time to apply their expertise as justified and needed. But, I will stop any DC signal from getting to my booster input, even if I have to build a circuit to do so. If I have to, I will try to build a circuit using the dual mode (DCC/DC) decoder in my old test locomotive to close a relay when it is powered and not in DC mode.
This may be of interest. I was testing an Atlas #200 Snap-Relay as part of a DC-Runaway-Protection circuit. It kicks-offs at >= 50%-Power DC signal, and stayed latched for a DCC only signal. (It also quickly over heats on the DCC signal!) There is an added benefit; it also kicked-off at power-up of the control unit. It stayed latched for an emergency stop and subsequent restart, but this may depend on the particular control unit being used.
DC-Runaway Information Pushing Emergency-Stop button on Dynamis causes DC-Runaway. Test setup is all Bachmann with exception of resistors and multi-meter. 1 k-ohm resistors were simulating an unintentional feedback across districts (such as a lighted passenger car with staggered wheel power pickup). Dynamis appeared to be in a confused state between stopping and short-detection-and-recovery. Power appeared to be cycling on/off at ~1 second cycle with no DCC signal. See "Dynamis & 5Amp Booster Power-Districts (part 1)" on YouTube for video.
I'm new to the forum, but not DCC. May I ask what is directly connected to each "power district"... are you running a booster, and then 2 circuit breakers and each breaker goes to one district? Whatever is between your booster output and the tracks, I'd like to know what it is, specific model and manufacturer. This should not happen with good wiring and quality equipment. I used to have runaways with cheap decoders, bad wiring about 10 years ago... Greg
I consider this to be an infrequent, but serious problem! This is an all Bachmann layout; even the wire leading to the resistors are Bachmann. The only exceptions are the 4 resistors crossing the two double gaps, and the millimeter (voltage setting) attached to the end of “layout” district. The Dynamis is new just out of the box and unmodified. The only exception is that I added a locomotive at address 5 for my test locomotive. I have no reason to suspect that any of the equipment is defective. All the track voltages, even under load appeared normal (no indications of a wiring problem). The same test was run with a completely unmodified Bachmann locomotive on address 3 with the same effect. The test locomotive was latter change in the “service” distinct from address 5 to address 8 by the Dynamis without any problem. The turnout was replaced with a Bachmann curve and the test rerun with the same effect. In other words everything that I could think of that might be reasonably causing the problem was eliminated. When the 1 kilo-ohm resisters I was using for test purposes were removed, the problem went away. There is a related thread in this section of this forum that might interest you; it is titled “DCC District Power from Dynamis?” I am not here to bash Bachmann, so if you what to identify the Bachmann products look at the pictures and use their web site. This thread is here in the hopes that it will help Bachmann and the train hobby world. I will not go into the reasons why it is here and is not on Bachmann’s forum. Then remainder of this reply is for Bachmann’s and only Bachmann’s benefit: I have many years experience as an embedded-systems-engineer/programmer, so I will give you some free (I a happily retired) advice: The emergency-stop button should be designed and implemented to be “fail-safe”. The Dynamis fault circuit/logic appears to be getting triggered by some minor feedback from the booster through the “Layout” district to the “Service” distinct and then to the Dynamis. [There was never a short or anything close to one.] The Dynamis design and/or program implementation then appeared to get confused between doing an emergency-stop and fault-detection-&-recovery. The only thing I found that got it out of its confusion was to power the unit down. This confused mode causes your DCC/DC dual-mode locomotives to take off at high speed. The only payment/acknowledgement I request is a fixed Dynamis, if and when this problem is addressed. I am happy to help in any way that I can!
Odd. When I read these threads, it really seemed like you needed help. That's okay. As far as the redesign, don't hold your breath. This system, if I recall from reading a while back, was a proprietary system purpose built for Bachmann by ESU, wasn't it? What that means (and I do have a bit of experience with OEM proprietary systems through Bachmann) is cost. To keep it to a price point, we drop whatever we need to do. If you read reviews on this system, from anyone but Kalmbach, they all have issues with it. Some small, some not so small. Silly things like two hands to hold the unit, the Pro add-on has a limited number of operators, addressing issues. Your 1Kohm add ons were the problem? Where did you find the advice to put 1Kohm resistors in? Just asking, as I want to go read it to understand the reasoning. Oh, and here are 3 quick reviews on the system. http://www.zealot.com/forum/showthread.php?t=164122 http://www.rmweb.co.uk/community/index.php?/topic/10438-review-of-dynamis/ http://www.dccconcepts.com/index_files/dccbrandecisions.htm Dave
Somehow my comment got lost. Can you reply to my previous questions: how are you wired up... I see a booster... but what is the wiring from that booster to the "power districts"? where is the extra electronics that makes them separate districts? Also, leaving resistors continuously between 2 DCC districts is not good, I believe it might "scramble" the logic in some circuit breakers. Regards, Greg
Sorry, I have been over sensitized by the product bashers/promotes that have not apparently concluded their problems with Bachmann. I think I will just ignore them from here on. As well as anybody that appears to be changing the topic into a personal attack on me. I made the wrong assumption that you had some knowledge of Bachmann’s “USA” products. It would help if you would better identify yourself. If doing so in public is a problem, you can contact me privately through the “Send Private Message” to me, RT_Coker. I will go ahead and assume that you motives are good (not a product basher or promoter). That said let me directly answer your questions plus a few more that might be asked. There is nothing between the booster and the “Layout” district track, but the short Bachmann cable that is used for the purpose of directly connecting to the EZ-track. There is nothing between the Dynamis and the “Service” district track, but this same type of short Bachmann cable. There is nothing between the Dynamis and the booster, but the standard cable that came with the booster for this purpose. The booster identification can be found here http://www.bachmanntrains.com/home-usa/products.php?act=viewProd&productId=1461. The identification of everything else except the resistors and the millimeter should be available at this site. The “test locomotive” may not be here, it is the only old Bachmann thing in the setup. But remember a nearly new and unmodified dual mode (DCC/DC) was used to the same effect. If you want to know how this problem surface and see a more complete description of the connections go to the related thread. It is titled “DCC District Power from Dynamis?”. Here is the link http://www.trainboard.com/grapevine/member.php?28125-RT_Coker. I will be happy to provide further clarification to you, but please identify yourself to me and clarify your interest in this topic. Bob
