Revo DCC Handset / CV29 help

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DGE-Railroad

DGE-Railroad

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'lo all

I'm looking for help with the Revo DCC handset (or possibly a sanity check from those geniuses who understand the CV value gubbins of DCC)

I'm in the process of installing a Revo DCC receiver and ESU Loksound into a Bachmann 2-truck Shay.

It's all gone quite well so far - the ESU decoder is testing well on the ESU testing board; lights and sounds coming on when they should, etc.
The Revo handset communication is all fine - sounds lights, etc.

My problem is with the motor control, which seems strange. Being a Shay, it has front and rear powered trucks - i've spliced these together to a common feed and hooked that up to the Loksound decoder motor output.
Direction control works fine but the drive seems lumpy and there is a distinct lag/speed difference between front and rear trucks.
Connecting up a variable bench power source directly to the truck wiring is fine, a you'd expect; both trucks smooth and working in parallel properly.

So it must be an issue with either the decoder or the Revo config. Both are set to 28 speed steps. I notice though that the Revo CV29 setup has Bit2 (ANALOG MODE) set to ON. It's how it arrived but surely this should be set to OFF?
The Revo manual states for it Bit 2: Analog Mode (No DCC decoder equipped locomotive). Reading around, CV29 Bit 2 would normally be expected to be set to off.

Can anyone confirm?
 
Greg Elmassian

Greg Elmassian

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So first, yes turn off analog control. That is in your decoder, not the revo receiver, so it was defaulted on from ESU, which is typical for DCC decoders.

See if there is any difference... I doubt it will make a difference.

Connecting a DC supply works differently than the PWM output from the decoder. See a difference?

So first, make sure any noise suppression inductors/capacitors on the motors are removed.

If you still have issues, you need to tune the ESU BEMF parameters. This is something you should read up and find other's experience with settings.

Greg
 
DGE-Railroad

DGE-Railroad

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Cheers Greg, I appreciate the input.

I also checked in with JK at Revo. He said the Revo bit2 CV setting shouldn't affect most decoders but should be switched off anyway. I'll do that as a first step.

That then leaves the decoder as the main culprit.

I'll check the motors for suppression; I'd completely overlooked that. I'm pretty sure they're simple cans though
IMG_1114.JPG

I've pulled the decoder out anyway, so I'll connect it up to the programmer and recheck the motor control settings too, paying attention to any back end ones
 
muns

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ESU decoders have a nice function that will allow it to "learn" the characteristics of the motors (in relation to BEMF) - I have found it works really well but I cant remember how to activate the process.
 
dunnyrail

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Just a little thought, if none of the above solutions work perhaps you could (if you can) see how each motor bogie on its own works with the Battery DCC system, I have a test rig wagon that I can hook up to just a power bogie if necessary with all the kit in the wagon and link wires to the bogies. Maybe just one power bogie for some reason is being rogue on DCC though why that would be is beyond me.
 
PhilP

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The plating looks quite worn-through on the wheels.. Could it be bad pickup, causing the decoder to keep resetting, perhaps?
 
Greg Elmassian

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The OP states "Direction control works fine but the drive seems lumpy "
To me that does not sound like starting and stopping or stuttering found from bad power pickup.

I'm sure it is BEMF related, the auto calibration suggestion by Mark is what I would do.
(Remember ESU, like many european manufacturers and not as familiar with the big Pittman and other high stall current motors favored in the US market)
High stall current motors can make BEMF systems nuts, I've seen it many times.

Here's a tutorial on how to do it: SBS4DCC - ESU LokSound Motor Auto-Tune

Greg

p.s. do not be overly obsessed with the 2 separate drive blocks not starting at the same time, this is common, and it will be much less under load, as the motor blocks share the effort to pull the train.
 
Last edited:
Hutch

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'lo all

I'm looking for help with the Revo DCC handset (or possibly a sanity check from those geniuses who understand the CV value gubbins of DCC)

I'm in the process of installing a Revo DCC receiver and ESU Loksound into a Bachmann 2-truck Shay.

It's all gone quite well so far - the ESU decoder is testing well on the ESU testing board; lights and sounds coming on when they should, etc.
The Revo handset communication is all fine - sounds lights, etc.

My problem is with the motor control, which seems strange. Being a Shay, it has front and rear powered trucks - i've spliced these together to a common feed and hooked that up to the Loksound decoder motor output.
Direction control works fine but the drive seems lumpy and there is a distinct lag/speed difference between front and rear trucks.
Connecting up a variable bench power source directly to the truck wiring is fine, a you'd expect; both trucks smooth and working in parallel properly.

So it must be an issue with either the decoder or the Revo config. Both are set to 28 speed steps. I notice though that the Revo CV29 setup has Bit2 (ANALOG MODE) set to ON. It's how it arrived but surely this should be set to OFF?
The Revo manual states for it Bit 2: Analog Mode (No DCC decoder equipped locomotive). Reading around, CV29 Bit 2 would normally be expected to be set to off.

Can anyone confirm?
Thinking outside the bits & not-bits of DCC, how close are you on amperage draw from the decoder to the power-trucks?
---Hutch
 
DGE-Railroad

DGE-Railroad

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ESU decoders have a nice function that will allow it to "learn" the characteristics of the motors (in relation to BEMF) - I have found it works really well but I cant remember how to activate the process.
Cheers Mark. :)

Yes indeed. I think I've managed to dig out a PDF that mentions it
CV54
If I exhaust the obvious, I'll resort to giving this a try, rather than guessing at settings!
It mentions running on a 3m track as it's a simple V-max test of the motor. I don't see any reason why that couldn't be a rolling road though...
 
DGE-Railroad

DGE-Railroad

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Just a little thought, if none of the above solutions work perhaps you could (if you can) see how each motor bogie on its own works with the Battery DCC system, I have a test rig wagon that I can hook up to just a power bogie if necessary with all the kit in the wagon and link wires to the bogies. Maybe just one power bogie for some reason is being rogue on DCC though why that would be is beyond me.
Thanks JonD. That's another very good thing to try I think. Trying one truck at a time on the decoder will at least show whether the symptoms are caused by running both motors in parallel, or whether it's a more fundamental control problem
 
DGE-Railroad

DGE-Railroad

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The plating looks quite worn-through on the wheels.. Could it be bad pickup, causing the decoder to keep resetting, perhaps?
A good spot Phil, it's not in fact using pickups now though; the carbon bushes and wiring for the track power have been removed and it's running off a bench supply currently.
 
DGE-Railroad

DGE-Railroad

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The OP states "Direction control works fine but the drive seems lumpy "
To me that does not sound like starting and stopping or stuttering found from bad power pickup.

I'm sure it is BEMF related, the auto calibration suggestion by Mark is what I would do.
(Remember ESU, like many european manufacturers and not as familiar with the big Pittman and other high stall current motors favored in the US market)
High stall current motors can make BEMF systems nuts, I've seen it many times.

Here's a tutorial on how to do it: SBS4DCC - ESU LokSound Motor Auto-Tune

Greg

p.s. do not be overly obsessed with the 2 separate drive blocks not starting at the same time, this is common, and it will be much less under load, as the motor blocks share the effort to pull the train.
Thanks for the find Greg.
I too, think the BEMF control is probably to blame. A simple test would be to turn it off completely which should to my mind, immediately remove the problem. I'll do the auto-tune trick though as its probably the best approach.

Although this is a second-hand decoder, I've re-written it with a factory configuration file for the Shay. This ought to have reset everything in the decoder to the factory defaults, which I suspect are unlikely to be correct for the motor.

Thinking back to my large-scale RC Car days, the first task after installing an ESC was to go through a back-emf test so that the speed controller could learn the motor characteristics. Expecting to use a speed controller (the ESU in this case) which uses BEMF, without first teaching it about the motor was a stupid mistake on my part...
 
DGE-Railroad

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Thinking outside the bits & not-bits of DCC, how close are you on amperage draw from the decoder to the power-trucks?
---Hutch
Thanks for another good suggestion Hutch. I think I should be okay; the Decoder, Receiver and Fuse are all 5A limited (in fact I'm pretty sure as a safety measure, I've used a 3A fuse initially, to see if it'd survive).
The power units are not 'under load' as such, as the loco could be when pulling/climbing so I'd expect the current draw to be low. It'd be interesting to measure though. I'll keep this in my back pocket in case the other suggestions bear no fruit...
 
Greg Elmassian

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It's hard to find a single loco (no matter how many motors) that can draw 5 amps continuously, even under heavy load.

The geared locos typically have such low gearing that the motor(s) rarely work hard.

Greg
 
Last edited:
Hutch

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It's hard to find a single loco (no matter how many motors) that can draw 5 amps continuously, even under heavy load.

The geared locos typically have such low gearing that the motor(s) rarely work hard.

Greg
You're absolutely right Greg, if nothing is malfunctioning. It was just a memory from an Aristo 0-4-0 that had a new defective motor that would surge and finally overheat.
---Hutch
 
muns

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Cheers Mark. :)

Yes indeed. I think I've managed to dig out a PDF that mentions it
CV54
If I exhaust the obvious, I'll resort to giving this a try, rather than guessing at settings!
It mentions running on a 3m track as it's a simple V-max test of the motor. I don't see any reason why that couldn't be a rolling road though...
I used a rolling road when I did this last, and if I recall what was originally a lumpy bad slow speed operating loco was smooth as a baby's bum after...go on....do it.
 
DGE-Railroad

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I'll do the auto-tune as soon as I get a chance, and report back but I'm expecting it to be the cure! Reading up about the load compensation, it'd make sense I think; the front truck has the additional drag of the drive line back to the imitation Shay cylinders, so the front and rear motors will be unevenly matched in terms of load.

I'd expect 'driving' it in order to auto-calculate the combined load/BEMF to result in a marked improvement :)
 
Greg Elmassian

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Thanks Hutch, in agreement on if nothing is wrong. Just wanted to validate the selection of decoder was fine for normal situation.

When I first started running articulated locos, and also when I was speed matching locos running free, I did obsess about everything running same speed.

Then a person wisely stated, that under load (not just the loco pulling itself) the loads to the motors even out... the "faster" loco will work harder and pull more amps, and the slower one will go to the same speed but pull less amps.

And yes, variations in motors, unless you want to buy $200 motors, will always allow one truck to start sooner.

Anyway, looking forwards to your results on the BEMF calibration.

Greg
 
stockers

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Maybe only as a test but cant you turn BEMF off. I have found this necessary when double heading powerful locos.
 
Greg Elmassian

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Good idea for a sanity check. Just a side comment, I have found in my experience some decoders where you could not completely turn BEMF off. I don't believe this is one of them, again, just a side comment.

Greg