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CV 54 and Motor Characterising; what exactly does it do?

leopardml2341

By leopardml2341,
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leopardml2341

leopardml2341

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Hello folks,

 

I know about CV54 and setting it to '0' to 'learn' the motor characteristics, but what does it actually do?

 

Perhaps more importantly, if this is applied to to separate locomotives, will each loco then respond identically to the selected speed step (assume inertia and all other motor control settings are same in each)?

 

Rgds,

 

Edit- missing 'to '0'' added

Edited by leopardml2341
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RFS

RFS

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I assume you are referring to Bachmann decoders which need CVs 54 and 55 setting to control the Back EMF for certain locos? Other makes of decoder do not use these.

 

The reason these CVs need adjusting is that the Bachmann decoders were designed for locos with flywheels which their current models do not have. Hence the need to adjust the CVs to avoid jerky starting and stopping.

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GoingUnderground

GoingUnderground

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Hello folks,

 

I know about CV54 and setting it to '0' to 'learn' the motor characteristics, but what does it actually do?

 

Perhaps more importantly, if this is applied to to separate locomotives, will each loco then respond identically to the selected speed step (assume inertia and all other motor control settings are same in each)?

 

Rgds,

 

Edit- missing 'to '0'' added

Setting CV54 to 0 and pressing "F1" is how you initiate the "Autotune" function in ESU 4th generation loco decoders, specifically the LokPilot V4 and LokSound V4 ranges. As I understand it, it sets up the Back EMF CVs to values suited to the characteristics of the motor to give users a starting point from which to "fine tune" the Back EMF CVs, specifically CVs 51 to 55 on ESU decoders. 

 

As I understand it, it doesn't affect the start voltage or speed table CVs, and it doesn't take into account the gearing between the motor and the driven axles or the diameter of the driven wheels, so I don't believe it would make locos respond identically to specific speed steps.

 

I don't know if other makes of decoder also have this "autotune" facility, or if it is just ESU 4th generation decoders. I was under the impression that it was unique to ESU, but I may be wrong.

Edited by GoingUnderground
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leopardml2341

leopardml2341

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CV54 is manufacturer specific so no assumptions can be made about what it does based on one manufacturer, except, of course, where one manufacturer is rebadging another's decoders.

True; as per OP I was looking for a bit more info when CV54 is specifically used for motor control 'tuning'.

Edited by leopardml2341
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leopardml2341

leopardml2341

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Setting CV54 to 0 and pressing "F1" is how you initiate the "Autotune" function in ESU 4th generation loco decoders, specifically the LokPilot V4 and LokSound V4 ranges. As I understand it, it sets up the Back EMF CVs to values suited to the characteristics of the motor to give users a starting point from which to "fine tune" the Back EMF CVs, specifically CVs 51 to 55 on ESU decoders.

 

As I understand it, it doesn't affect the start voltage or speed table CVs, and it doesn't take into account the gearing between the motor and the driven axles or the diameter of the driven wheels, so I don't believe it would make locos respond identically to specific speed steps.

 

I don't know if other makes of decoder also have this "autotune" facility, or if it is just ESU 4th generation decoders. I was under the impression that it was unique to ESU, but I may be wrong.

Thanks Keith, sorry for late response, I had in mind locos (or motor bogies) of identical type when I typed the OP, but regretfully I forgot to put that in the post :senile:

 

Rgds,

Edited by leopardml2341
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GoingUnderground

GoingUnderground

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Thanks Keith, sorry for late response, I had in mind locos (or motor bogies) of identical type when I typed the OP, but regretfully I forgot to put that in the post :senile:

 

Rgds,

I think it unlikely that you would get what you want. 2 identical locos often don't run at the same speed when put on the same track under DC. If it's a continuous circuit, one will often catch up with the other sooner of later. We're not prepared to pay the higher cost that better manufacturing standards and tolerances, both electrical and mechanical, that identical performance would require.

 

If you want that then you will have to play around with the CVs that control start speed, and the speed tables until you achieve your aim of identical performance. But even then it might vary between bogies according to the ambient temperature if changes in temperature cause differential changes in friction within the drive trains between identical bogies.

Edited by GoingUnderground
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Crosland

Crosland

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True; as per OP I was looking for a bit more info when CV54 is specifically used for motor control 'tuning'.

The point is that two different manufacturers can use it in completely different ways, even if the purpose ("motor tuning") is the same.

 

Similarly, two manufacturers could have exactly the same "motor tuning" method, using completely different CVs.

 

There are no common specs for manufacturer specific CVS.

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