That would be a very buggy decoder, and not a brand I would want to use if they all behave that way. But before tossing it, I would find out what kind it is and do a reset. It could be one of those CVs that you aren't supposed to set since they aren't listed in the instructions got set somehow. Or just got corrupted. A reset fixes many things.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
CSX RobertIf it is the same issue, here is what is happening - when the decoder has momentum enabled, as it is going through it's momentum delay it will miss other speed commands(this is not how they are supposed to work, but these had a bug in them). Say you turn the speed up to 10 and the decoder starts to accelerate. You then turn the speed back down to zero, but the decoder will continue to accelerate until it reaches 10 because it does not see the speed packets addressed to it. Once the decoder reaches 10, what happens at that point will actually depend on the DCC system you are using and how it is configured.
if i understand you correctly, the command to slow down is ignored and the loco continues to accelerate as if no command was sent until it reaches the set speed (10). Is this correct?
in our case, the loco speed increased abruptly when we issued the command to slow down. It didn't seem to ignore the command.
thanks
greg - Philadelphia & Reading / Reading
I do remember reading about people having this type of problem with certain decoders(I do not remmeber the brand or if it happened with more than one model). If it is the same issue, here is what is happening - when the decoder has momentum enabled, as it is going through it's momentum delay it will miss other speed commands(this is not how they are supposed to work, but these had a bug in them). Say you turn the speed up to 10 and the decoder starts to accelerate. You then turn the speed back down to zero, but the decoder will continue to accelerate until it reaches 10 because it does not see the speed packets addressed to it. Once the decoder reaches 10, what happens at that point will actually depend on the DCC system you are using and how it is configured.
On NCE, there is a "Number of Stop Packets" setting. If it is set to a non-zero number, when you turn a throttle down to zero, the command station sends that number of stop packets to the loco address and then stops sending packets to that address. In the above case, it would be likely that the command station would have stopped sending stop packets by the time the loco reached it's target speed, so the loco would not see anymore speed packets and just continue on at speed ten.
If "Number of Stop Packets" is set to zero, the command station actually sends a continuous stream of stop packets for every loco that has been run since the system was powered up(up to the systems memory limit). With this setting, in the above case once the lcoo reached speed ten it would stop accelerating, see a stop packet, and then slow to a stop. The bad thing about this setting is that on a large layout with a large number of locos, it can reduce system response.
CV's 3 and 4 control accelleration and decelleration respectively. I usually set them to 0 as I don't care for the effect they provide.
rrinkerCould be dirty track, wheels, or pickups, bad track bus design causing poor signals, or a defect in the command station or booster.
this was very repeatable on different parts of the layout with two different controllers (NCE).
this is a very large layout that doesn't have problems with other locos sharing the same command stations using the similar controllers (NCE)
rrinkerOr the decoder is just bad.
faulty or buggy?
Not that I am aware of. That is not proper behavior. If you have momentum enabled, crank the throttle to 50, but before the loco reaches that speed, dial down to 25, it should stop accelerating at 25, or if it is already past 25%, slow down (gradually if deceleration is set, CV4). It should not keep increasing speed. That tells me it either missed the speed command, or misread it as a higher speed than it was originally set to. Could be dirty track, wheels, or pickups, bad track bus design causing poor signals, or a defect in the command station or booster. Or the decoder is just bad.
had an odd experience with a loco with a lot of momentum. if the loco speed was turned up to 10 for example, and before it reached that speed due to momentum, it was set back to zero, the loco to sped up. Someone usually caught it and stopped it before we could see what it would do over time.
My guess is that decreasing the speed step caused it to decrease speed from the previously set speed (10), not it's actual speed (<10). Since, because of momentum its actual speed was far less than the set speed, it sped up, and i'm guessing that if we hadn't stopped it, we would have noticed that it was slowing down.
wasn't my loco and do not know what type of decoder it had, except to say it had sound and lots of momentum
Is there any CV that might cause this behavior?