Bemf

[Andymsa]

Hi all

 

I'm not sure really how to put this question but I give it a go. I have asked this on other forums but not had a good reply yet so I thought I would ask here.

 

I have a dh163 decoder and I'm setting it up for use in traincontroller, I set up cvs 2,5,6 according to rudys videos for those who are familiar with those videos I then run speed profile in traincontroller, but I have noticed that I get a speed surge when the loco is accelerating at a specific point. By trial and error so far I worked out turning bemf off seems to resolve this surge but cv 2 has to be set very high to get a crawl speed at step 1 also there is a different speed forwards and backwards that's not there when bemf is on. So should I have bemf on or not and how do I get rid of the speed surge with it on.

 

Andy

[RFS]

I've experienced this problem in the past, especially when I was using TCS decoders. Turning BEMF off resolved that issue, but that caused issues with slow running as you have found. It's also not an option when you are using Traincontroller. You will have profiled the loco "light engine", and when running with a loaded train on schedules, TC will assume that BEMF will maintain the correct speed. With BEMF turned off, you'll find that trains do not stop in the right place. 

 

Replacing the TCS decoders with Lenz Standard+ ones resolved the issue for me. It seems to me the Digitrax DH163 has the same issue with BEMF as I had with TCS (and also when I tried a couple of DCC Concepts decoders). I also now have a few locos with Zimo decoders, and their BEMF implementation is also accurate like the Lenz ones. 

[Andymsa]

I've experienced this problem in the past, especially when I was using TCS decoders. Turning BEMF off resolved that issue, but that caused issues with slow running as you have found. It's also not an option when you are using Traincontroller. You will have profiled the loco "light engine", and when running with a loaded train on schedules, TC will assume that BEMF will maintain the correct speed. With BEMF turned off, you'll find that trains do not stop in the right place. 

 

Replacing the TCS decoders with Lenz Standard+ ones resolved the issue for me. It seems to me the Digitrax DH163 has the same issue with BEMF as I had with TCS (and also when I tried a couple of DCC Concepts decoders). I also now have a few locos with Zimo decoders, and their BEMF implementation is also accurate like the Lenz ones.

 

You have confirmed my thinking, as I don't have this issue with ESU decoders or it appears that I don't. I shall do some tests with traincontroller and its stopping position. But as I use specific stopping sections and don't relie on just using one detection section in traincontroller I don't think getting trains to stop in right place will be an issue. My only concern turning bemf off is I have a number of spirals and trains slowing to me ch on them may be an issue.

[Andymsa]

Update

 

With further testing it was found that cv57 bemf is the issue, on digitrax decoders this is set a 6 by default I set up his to a value of 2 or 3 and this seems to give better smooth acceleration. I now have to test on layout and my spirals with a train.

 

With traincontroller I had no issues with bemf turned on or off and getting loco to stop in correct place

 

Update

 

I tried it with a train tonight going up or down sprials it ran jerky and slowed at times and raced down the sprials. I tried the same loco with a ESU decoder, it ran like a dream. On further investigation this seems to be an bigger issue with digtrax chips and all depends on the locomotive motor and chip combo. So I will be using ESU chips from now on.

 

 

 

Andy

Edited June 7, 2018 by Andymsa