Zimo decoders, Traincontroller and accurate stopping

[RFS]

Having recently upgraded from Lenz DCC to Z21, I’ve been able to update the firmware of my Zimo decoders, all of which are now 40.5.  But I’ve had a couple of problems.

 

Firstly, my 4 Bachmann 2EPBs with level 36.5 thereafter started overrunning the TC stopping points – by around a coach length. And all 4 did it and in all blocks. So I was forced to reprofile them all, after which normality returned, or so it seemed.

 

I check the accuracy by running reprofiled engines on a shuttle between the main station and the previous block, to check when they re-enter they stop at the correct point. They all did. But when subsequently entering the same station block on a schedule they all pull up short by at least 10cm. And consistently. Using the following 3 blocks I set up 2 shuttle (there and back) schedules: first from station to transit and back, and the second from station via transit to yard and back.

 

 

On the first the units stop correctly, and on the second they stop short. I tried my other Zimo-fitted engines (all of which also had to be reprofiled) – 2 Bachmann 4CEPs and 2 Hornby steamers, and they all do the same. 2 Bachmann 4CEPs with Lenz Silver21+ decoders don’t exhibit this characteristic.

 

Seems to me something to do with Back EMF, but all my Zimo-fitted locos use standard decoder defaults. Is it perhaps sampling over a longer run that is the issue? I did try running one 2EPB on the 2-block schedule, and when it reached the stop in the transit block, I pulled it back a couple of feet to lengthen its return . Sure enough it arrived back at the station and stopped short. So it looks like the longer run is the issue?

 

The CVs for Back-EMF are complex, involving CVs 9, 10, 56, 58 and 113 amongst others. I've tried tweaking various of these but cannot eliminate the inconsistent stopping. 

 

Any Zimo experts in the house?

Edited August 29, 2021 by RFS

[jpendle]

Not me, but.

 

All my loco's have Zimo decoders. I also use a Z21 and have been upgrading the firmware in my decoders on an occasional basis.

 

I discovered by accident that something changed from earlier versions of firmware, an N Gauge loco with an MX622N ran over twice as fast after upgrading the firmware from 31.5 to 37.8, I never found out what Zimo had done to make this happen. So I would expect that a loco could well run at different speeds depending on the brand of decoder fitted.

 

One other thing I've noticed is that with CV5 set to 1(255) ,which is the default, all my locos max out at about speed step 70 and then exhibit very erratic speeds up to SS128.

As a result I've had to set CV5 to around 120 to get a reasonable response from the decoders between SS1 to SS128.

 

I use iTrain not Traincontroller, which I hope isn't relevant, but with CV2 set to 20 and CV5 set to around 120 I have not seen any speed profile issues with any of my Zimo equipped locos, other than those which could be attributed to the locos actually getting run in properly, at last 

 

I am also running all my locos at revision 40.5.

 

Hope some of that helps.

 

Regards,

 

John P

 

 

[NIK]

Hi,

 

I am not a Zimo expert at all but you could try increasing the speed step at which back EMF turns off (set CV10 to 252 for example). Then the Zimo decoder should stop using its Back EMF curve and use the same Back EMF compensation at all speed steps.

 

However if it is warming up of the mechanism that is throwing stopping out I would have expected the trains to run further not shorter when htey warm up.

 

Regards

 

Nick

[Andymsa]

16 hours ago, RFS said:

Having recently upgraded from Lenz DCC to Z21, I’ve been able to update the firmware of my Zimo decoders, all of which are now 40.5.  But I’ve had a couple of problems.

 

Firstly, my 4 Bachmann 2EPBs with level 36.5 thereafter started overrunning the TC stopping points – by around a coach length. And all 4 did it and in all blocks. So I was forced to reprofile them all, after which normality returned, or so it seemed.

 

I check the accuracy by running reprofiled engines on a shuttle between the main station and the previous block, to check when they re-enter they stop at the correct point. They all did. But when subsequently entering the same station block on a schedule they all pull up short by at least 10cm. And consistently. Using the following 3 blocks I set up 2 shuttle (there and back) schedules: first from station to transit and back, and the second from station via transit to yard and back.

 

 

On the first the units stop correctly, and on the second they stop short. I tried my other Zimo-fitted engines (all of which also had to be reprofiled) – 2 Bachmann 4CEPs and 2 Hornby steamers, and they all do the same. 2 Bachmann 4CEPs with Lenz Silver21+ decoders don’t exhibit this characteristic.

 

Seems to me something to do with Back EMF, but all my Zimo-fitted locos use standard decoder defaults. Is it perhaps sampling over a longer run that is the issue? I did try running one 2EPB on the 2-block schedule, and when it reached the stop in the transit block, I pulled it back a couple of feet to lengthen its return . Sure enough it arrived back at the station and stopped short. So it looks like the longer run is the issue?

 

The CVs for Back-EMF are complex, involving CVs 9, 10, 56, 58 and 113 amongst others. I've tried tweaking various of these but cannot eliminate the inconsistent stopping. 

 

Any Zimo experts in the house?

was there a particular reason you upgraded the firmware, personally I would of left it alone if no issues were being experienced. Is it possible to revert back to the previous firmware version ?

[Nigelcliffe]

2 minutes ago, Andymsa said:

was there a particular reason you upgraded the firmware, personally I would of left it alone if no issues were being experienced. Is it possible to revert back to the previous firmware version ?

 

In general, yes reversion is possible.  One can usually load any firmware version onto a Zimo decoder.   

 

I agree, I'd only upgrade "in service" locos if there was a new feature required, or problem being fixed.   Its a different matter to upgrade "experimental" locos on the bench. 

 

- Nigel

[RFS]

Several of my MX600Rs were level 31.63 which is quite old, and I do prefer to have any firmware at the current level. I was not expecting the upgrades to cause any problems though! 

 

I have tried to revert a 2EPB back to 36.5 but I can't at the moment get it to work. When upgrading with the Z21, I had to press CTRL + ALT + Z to override the checks and indeed that worked fine. But this technique now does not work installing back to 36.5. I have emailed Zimo with the issue and asked them if there's anything I need to do to regress. 

 

Thanks for your comments and I will report back when I hear from Zimo. 

[jpendle]

FWIW

 

I have updated all my locos at least twice now and as far as I can tell it has not introduced any issues.

As I said in my earlier post going from 31.5 to 37.8 changed the speed of locos that had been upgraded.

BUT this was a good thing as two otherwise identical locos would run at different speeds depending on the firmware revision of the installed decoder. This made double heading problematic.

 

What do the Traincontroller speed profiles look like?

 

Regards,

 

John P

[Nigelcliffe]

My upgrades are with a Zimo device, not the Z21.   So don't know if the Z21 introduces a few barriers not present elsewhere. 

[RFS]

The speed profile of the 4CEP looks like this - 

 

 

Actually done with 128 steps but TC seems to always display as 28 subsequently. I prefer to have a nice steady transition, so to get this speed profile I first test max speed and reduce CV 5 until it runs at no higher than 70 MPH. I then measure at speed step 63 and adjust CV 6 until it runs at about 30 MPH. This gives good peformance with TC. Here CV 5 is 120 and CV 6 is 80. 

 

The problem with the Z21 is it only updates automatically Roco-recognized decoders. The MX634D is not one of these but I do have one 4CEP with MX638 which is OK for the Z21, so I'll try that on 36.5 tomorrow and see what happens. 

Edited August 30, 2021 by RFS

[Andymsa]

7 minutes ago, RFS said:

The speed profile of the 4CEP looks like this - 

 

 

Actually done with 128 steps but TC seems to always display as 28 subsequently. I prefer to have a nice steady transition, so to get this speed profile I first test max speed and reduce CV 5 until it runs at no higher than 70 MPH. I then measure at speed step 63 and adjust CV 6 until it runs at about 30 MPH. This gives good peformance with TC. Here CV 5 is 120 and CV 6 is 80. 

 

The problem with the Z21 is it only updates automatically Roco-recognized decoders. The MX634D is not one of these but I do have one 4CEP with MX638 which is OK for the Z21, so I'll try that on 36.5 tomorrow and see what happens. 

so the above graph is for the cv set to 120 and cv 6 to 80. I can’t understand why the max speed set in TC is for 85. Does not this confuse what TC thinks the train is travelling at and distance covered before the stop point if using offset markers. I try to get cv 5 as close to the max speed set in TC

[jpendle]

The Z21 will update any Zimo decoder.

 

Here's the secret sauce 

 

Make sure that CV144 is set to 0 and that DC running is OFF in CV29.

Then in the maintenance app, instead of pressing the update button, press Ctrl + Alt + Z.

I have tried this and it does work, the original document, that is on RMEB somewhere, came from a Zimo employee.

 

Regards,

 

John P

[melmerby]

With the Zimo decoders that I have, I have straightened the inbuilt "S" shape speed profile, using the speed curve CVs

This is something I never have to do with Lenz decoders as ther are pretty straight to start with.

[RFS]

36 minutes ago, jpendle said:

The Z21 will update any Zimo decoder.

 

Here's the secret sauce 

 

Make sure that CV144 is set to 0 and that DC running is OFF in CV29.

Then in the maintenance app, instead of pressing the update button, press Ctrl + Alt + Z.

I have tried this and it does work, the original document, that is on RMEB somewhere, came from a Zimo employee.

 

Regards,

 

John P

 

Yes that is what I had to do with the MX634s to update them to 40.5 in the first place. But now this does not work when trying to go back to 36.5. When the error box comes up, I clear it, hit ctrl + alt +Z, the update starts again but then the error box comes up once more. DC running is off in all my decoders and I verified CV144=0. 

[RFS]

2 hours ago, Andymsa said:

so the above graph is for the cv 5 set to 120 and cv 6 to 80. I can’t understand why the max speed set in TC is for 85. Does not this confuse what TC thinks the train is travelling at and distance covered before the stop point if using offset markers. I try to get cv 5 as close to the max speed set in TC

 

85 is just the default. When you profile a decoder, the process will end once it reaches 85 even though it's not got to speed step 28 or 126. None of my locos are allowed above 70 MPH as anything above that speed looks quite wrong, and results in the train being signal-checked before being allowed back into the storage yard, as all roads are shared with 2,3 or 4 trains per road using separate blocks.

Edited August 30, 2021 by RFS
Clarification

[RFS]

18 minutes ago, melmerby said:

With the Zimo decoders that I have, I have straightened the inbuilt "S" shape speed profile, using the speed curve CVs

This is something I never have to do with Lenz decoders as ther are pretty straight to start with.

 

Indeed Lenz seem much simpler. This is the other 4CEP I've been using in testing which has a Silver21+ decoder. CV 5 is 180 and CV 6 is 48. 

 

 

[Andymsa]

9 minutes ago, RFS said:

 

85 is just the default. When you profile a decoder, the process will end once it reaches 85 even though it's not got to speed step 28 or 126. None of my locos are allowed above 70 MPH as anything above that speed looks quite wrong, and results in the train being signal-checked before being allowed back into the storage yard, as all roads are shared with 2,3 or 4 trains per block.

is that not a waste of the top end speed steps, surly using all speed steps will give smoother acceleration and braking. The method is use is that I will set cv 5 to the top max speed and set TC to that max speed that way all speed steps are employed.

 

obviously you use the TC line up function, personally I don’t like that. As I have 7 storage yards each yard is for specific types of trains so I can have blocks to the required length of train that uses the storage yard.

[RFS]

20 minutes ago, Andymsa said:

is that not a waste of the top end speed steps, surly using all speed steps will give smoother acceleration and braking. The method is use is that I will set cv 5 to the top max speed and set TC to that max speed that way all speed steps are employed.

 

obviously you use the TC line up function, personally I don’t like that. As I have 7 storage yards each yard is for specific types of trains so I can have blocks to the required length of train that uses the storage yard.

 

No it does not waste speed steps. By setting CV 5 to the maximum speed you want for the loco you then get all 126 speed steps to use.

 

I don't use the TC line-up function - it's far too slow as it moves trains at threshold speed (it was designed for a stack of locos not trains). What I meant to say was 2,3 or 4 trains per storage road: there are separate blocks for each, and when one train leaves the rest move up automatically. I will edit the original post....

[melmerby]

2 hours ago, Andymsa said:

is that not a waste of the top end speed steps, surly using all speed steps will give smoother acceleration and braking. The method is use is that I will set cv 5 to the top max speed and set TC to that max speed that way all speed steps are employed.

 

N.B. not all decoders go to 255/6, I have a Lok Pilot (old) which only goes to 64.

But 64 is the same as 256 in another decoder and pro rata.

Very few of my locos use the max speed setting.

Apart from the Lok Pilot which is set to 32, the lowest Vmax is 81 and the highest is 255.

 

I set the required loco max speed with CV5, profile the loco then I set TC to the same max (anything from 40 to 90mph).

That way the speedo doesn't have a large unused area.

Edited August 30, 2021 by melmerby

[melmerby]

On 30/08/2021 at 20:54, RFS said:

 

Indeed Lenz seem much simpler. This is the other 4CEP I've been using in testing which has a Silver21+ decoder. CV 5 is 180 and CV 6 is 48. 

 

 

Thats bad for a Lenz decoder, I often get profiles like this using V start at 1, Vmid at half of Vmax:

 

Lenz Standard + (V1.0)

 

 

 

Edited April 21, 2022 by melmerby

[Andymsa]

18 minutes ago, melmerby said:

N.B. not all decoders go to 255/6, I have a Lok Pilot (old) which only goes to 64.

But 64 is the same as 256 in another decoder and pro rata.

Very few of my locos use the max speed, apart from the Lok Pilot which is set to 32, the lowest is 81 and the highest is 255.

 

I set the required loco max speed with CV5, profile the loco then I set TC to the same max (anything from 40 to 90mph).

That way the speedo doesn't have a large unused area.

exactly how I do it. When I was talking about max speed I meant the max speed that is set by the user not cv 5 set to 255

[Nigelcliffe]

10 hours ago, RFS said:

 

No it does not waste speed steps. By setting CV 5 to the maximum speed you want for the loco you then get all 126 speed steps to use.

 

I don't use the TC line-up function - it's far too slow as it moves trains at threshold speed (it was designed for a stack of locos not trains). What I meant to say was 2,3 or 4 trains per storage road: there are separate blocks for each, and when one train leaves the rest move up automatically. I will edit the original post....

 

In the Zimo manual, it suggests using CV57 to control motor speed.    If one has an extreme loco (eg. one with a 3v motor which does 200mph in a shunter), then using CV5  to a really low value doesn't give good control, whereas setting CV57 first to limit the range of speeds does give good control.

 

The manual says:   " CV #57 can also be used as an alternative to CV #5 (top speed), which has the advantage that the full resolution of the 255 speed steps remains available  "

 

 

- Nigel

[RFS]

9 hours ago, melmerby said:

That's bad for a Lenz decoder

 

It was actually profiled using 128 speed steps not 28, but TC always displays as if it were using 28. This often results in a display of the profile that is not as smooth as it actually is. 

[RFS]

Spent some time this morning trying to downgrade the firmware and cannot get it to work. I have MX600R, MX634 and MX638 deocders, and although the MX634 is not an official Roco one, the other two are. When the update fails, I uncheck the "CV Verification" box and hit ctrl+alt+Z but it still comes back and says the decoder is not supported. Tried also using the 1.5 maintenance tool, and downgrading the Z21 firmware to 1.40 from 1.41, again with no success.

 

I have asked Zimo for comments on why the decoder performance has changed, and I will now ask Roco why their Maintenance Tool won't work for me. 

[RAF96]

Does the decoder firmware upgrade not come with user notes telling of what advantage is gleaned from the upgrade. It may just be better compatibility with alien controllers in which case no benefit may be realised.

[jpendle]

4 minutes ago, RAF96 said:

Does the decoder firmware upgrade not come with user notes telling of what advantage is gleaned from the upgrade. It may just be better compatibility with alien controllers in which case no benefit may be realised.

 

4 minutes ago, RAF96 said:

Does the decoder firmware upgrade not come with user notes telling of what advantage is gleaned from the upgrade. It may just be better compatibility with alien controllers in which case no benefit may be realised.

Yes it does.  The firmware upgrades are always enhancements and bug fixes. I've not seen any that are directly related to other DCC systems/controllers.

Although they describe the enhancements in detail, they usually don't explain what bugs have been fixed.

 

Regards,

 

John P