CV 56 and Back EMF on Heljan 7mm and other locos

[richard carr]

I run all my Heljan and now some of my JLTRT locos with one sound chip either a Loksound or the XL version some have 3.5s and others are version 4, it powers both motors wired in parallel. CV 56 was set to maximum on all the decoders I have on the version 4s this was based on their auto setup procedure. The JLTRT locos are powered by 2 ABC gearboxes with Maxon 6 watt motors

One thing I have noticed is that slow speed running is jerky, its definitely not smooth. So I have been playing around with the setups. After reading the loksound version 4 manual it became clear to me that either no back emf would be the solution or reduced back emf. This is achieved by altering CV 56, if you set it to zero then that turns off back emf altogether. I tried this, the loco runs smoothly but it often didn't even start to move until I had 30 showing on the controller, yet sometimes it started at 23. I know I can adjust the start voltage to remove some of this but I thought I would try a reduced back emf effect instead.

So I set CV 56 to 15 (the maximum is 64), this works great you still get some load control but its much much smoother at low speed. I then tried 20, 25 and 10, it was hard to tell much difference between them although 25 did seem to be a bit more jerky. So I have settled on 15 and all my locos are running much better than before. There is no difference between the Heljan motors and the maxon ones and no difference between any of the decoders.

I'd be interested to hear the results from anyone else if they try this.

Richard

 

[Steph Dale]

Richard,
Have you tried the CV54 trick with your Loksound v4 decoders? Works a treat and tends to retain feedback. I leave feedback on all my DCC locos as the very high sampling frequency means it doesn't do any harm at all. It's only really necessary to dial it back if you're double heading locos, it'll stop the locos 'fighting'.
The routine in the manual for the v3.5 decoders is worth following in its entirety, you will get rid of any hunting or run away if you spin through the routine twice.
I suggest you also set CV29 to allow digital-only operation, this will help too.
Steph

 

[richard carr]

Steph

Yes all my V4 Loksound decoders were initially setup with the CV 54 trick, but it leaves back emf on at full value. The running at moderate speeds and above is fine but low speed is very noticeably jerky and that is what I wanted to improve.
I will have a look at the routine in the manual for V3,5 decoders and try your suggestion with CV 29.

Thanks

Richard

 

[TheSnapper]

I'll see if I can dig out some old saved settings.

My 3.5XL Hymek and V.4 Class 20 ran beautifully at slow speeds, as did my JLTRT/ABC-Canon/3.5XL Class37

I've gone totally Zimo now, but I think I saved CV settings in text files.

Tim

 

[TheSnapper]

Richard/Steph

I have managed to find a couple of saved files only, which may be of interest.

The file "Hymek_12May2010.pdf" is a list of the final settings for my Loksound 3.5XL fitted Heljan Hymek, before I sold it.

I also have a file "2020_June2013.esux" which is the saved config for my Heljan Class 20 fitted with a Loksound V.4 (NB:not XL). , I think you may need a Lokprogrammer to write it to a chip. If you want to try it, I cannot easily upload it here, but can send it by e-mail.

HTH

Tim

 

[richard carr]

Thanks Tim, its always nice to have something to compare againt.

Richard