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Very Poor Low Speed DCC Control of CD-ROM Motors

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I've installed CD-ROM type motors in quite a few of my old (circa 1981) Lima / Hornby locomotives and DMUs with a good success rate. I've been mostly using Hatton's own 8-in 4-function DCC decoders.

 

However, I've got problems with 2 recent 'conversions'. One is the same CD-ROM motor + Hattons DCC decoder and the other a CD-ROM + Gaugemaster DCC27 8&21-pin 4-function DCC decoder. On both of these, the motor starts very abruptly at speed step-1, even with start voltage of 0 (and yes, the acceleration was set to a figure of ~30). The only way I've found to stop this behaviour is to turn off the back EMF, but I don't want to do this as it makes general running (and hauling power) a lot worse.

 

I've a number of locos with the CD-ROM motor + Hattons DCC decoder combination working without any issues, so I guess there is some 'variation' in the CD-ROM motors (?).

 

Any ideas on how to overcome this problem? I've wondered about putting a resistor in series with the CD-ROM, but have no idea what would be a 'good' value for the resistor.

 

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Are they 12 V motors or lesser mortals, as some are as low as 3 V which means they are essentially on or off under DCC or DC control.

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2 hours ago, RAF96 said:

Are they 12 V motors or lesser mortals, as some are as low as 3 V which means they are essentially on or off under DCC or DC control.

 

I am sure they are <12v by some margin. Hence I always limit the motor voltage to 96 or 128 instead of 255 (full voltage). For the majority of them I have no issues.

 

I did swap out the DCC27 DCC decoder for a bog-standard Hattons one, and that fixed that locomotive. I'll be sending back my other DCC27s for a refund .... :read:

 

That still doesn't explain the one loco I have with CD-ROM + Hattons DCC decoder that 'jump starts' ... :help:

 

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I think with Gaugemaster decoders, a value of 0 in CV2 means something other than zero volts.  I have a couple of DC23s with the value in one set at 2 and the other at 3.  One of the motors is rated at 4volts and i have CV5 set at 20 for a maximum speed of about 25mph.

 

Harold.

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12 hours ago, HLT 0109 said:

I think with Gaugemaster decoders, a value of 0 in CV2 means something other than zero volts.  I have a couple of DC23s with the value in one set at 2 and the other at 3.  One of the motors is rated at 4volts and i have CV5 set at 20 for a maximum speed of about 25mph.

 

Harold.

Harold,

 

Interesting. I also found something about putting 2 in CV30 to load the 'default' values, which I interpret as being different to putting CV8 to a value of 8 (reset).

 

Anyhow, I think I'll give up with the Gaugemaster DCC27 and return them to the shop for a refund.

 

That just leaves me with one Hattons + CD-ROM motor combination that 'jump starts'. Any ideas on how to resolve that one?

 

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Have you tried a Zimo decoder, very good control of everything and a MX617 is only £20

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7 hours ago, WIMorrison said:

Have you tried a Zimo decoder, very good control of everything and a MX617 is only £20

Iain,

 

Not been a Zimo user, so had to look the MX617 up on the interweb. For my uses, I'd need the one with the 8-wires, and that costs £30. Thanks for the idea though, it may come in useful sometime.

 

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8 minutes ago, ISW said:

Iain,

 

Not been a Zimo user, so had to look the MX617 up on the interweb. For my uses, I'd need the one with the 8-wires, and that costs £30. Thanks for the idea though, it may come in useful sometime.

 

Lenz Standard Plus V2:

https://www.dccsupplies.com/item-p-110760/lenz-standard-plus-v2-decoder-10231-02.htm

https://www.dcctrainautomation.co.uk/lenz-10231-02-standard-decoder.html

Every bit as good as Zimo

Edited by melmerby

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MX600 is a brilliant decoder and with a bit of soldering it allows also a stay alive function. I have currently 20 in use. They allow to change the control characteristics so they can be adapted for practically every motor. There are some examples for standard motors in the manual. You can make your own experiments to improve whatever you have.

 

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16 hours ago, melmerby said:

 

13 hours ago, Vecchio said:

MX600 is a brilliant decoder and with a bit of soldering it allows also a stay alive function. I have currently 20 in use. They allow to change the control characteristics so they can be adapted for practically every motor. There are some examples for standard motors in the manual. You can make your own experiments to improve whatever you have.

 

 

Thanks for the decoder recommendations. These will help inform me when I'm buying my next decoders.

 

However, I really haven't found a solution to my original problem - why do some decoder+motor combinations result in a 'jump start' unless the BEMF is turned off? Surely there must be a combination of CVs that can mitigate the problem?

 

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On 06/11/2019 at 10:07, ISW said:

Harold,

 

Interesting. I also found something about putting 2 in CV30 to load the 'default' values, which I interpret as being different to putting CV8 to a value of 8 (reset).

 

Anyhow, I think I'll give up with the Gaugemaster DCC27 and return them to the shop for a refund.

 

That just leaves me with one Hattons + CD-ROM motor combination that 'jump starts'. Any ideas on how to resolve that one?

 

Hi,

 

If the CD-ROM motor is less than 12V and your DCC system applies ~12V pulses to the motor you can hardly ask for a refund.

 

Regards

 

Nick

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5 minutes ago, NIK said:

Hi,

 

If the CD-ROM motor is less than 12V and your DCC system applies ~12V pulses to the motor you can hardly ask for a refund.

 

Regards

 

Nick

And I would definitely agree with that statement. Cheating generally gets you nowhere ...

 

The DCC27s I returned were a 5-pack, unopened and unused :angel:. I had a single DCC27 from a previous purchase (from the same shop actually) that I had the problems with. Not wishing to compound the problem, I returned the 5-pack. I suppose I should have 'tested' the single DCC27 more thoroughly before buying the 5-pack :banghead:.

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12 minutes ago, ISW said:

...However, I really haven't found a solution to my original problem - why do some decoder+motor combinations result in a 'jump start' unless the BEMF is turned off? Surely there must be a combination of CVs that can mitigate the problem?

Given that you know that a slow speed start is obtainable with BEMF not active, it is probably the BEMF constants that you want to access. These do not necessarily have addressable CV's provided, a search of the manual for the decoders you have is required (I have no relevant experience to offer for the products mentioned).

 

If the decoders provide no such options then two choices offer:

Replace motor. (May be the best plan, I think you may have a 3 to 4V unit rather than 12V.)

Use a decoder with the required adjustments.

 

If going the decoder route, while I generally use Lenz as the lowest price for a quality drive that works with any decently sorted mechanism, when there is 'motor taming' to be achieved, the first choice as already mentioned above is Zimo. (They have now obliged with a lower cost decoder too, in the MX6xx series, a very welcome development.) You have to be prepared to read the manual in detail and do some experimentation to get to a result, but Zimo decoders deliver. (I am sure someone will have found a totally untameable motor, but I have yet to find one that cannot be cudgelled into submission...)

 

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Note.

Some of these "CD" motors are as low as 1.5v rating for use in solar powered equipment and would likely be totally useless in a loco.

Just because they look the same, they aren't necessarily the same.

Even CD player motors aren't all the same voltage.

 

 

 

 

Edited by melmerby

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2 hours ago, melmerby said:

Note.

Some of these "CD" motors are as low as 1.5v rating for use in solar powered equipment and would likely be totally useless in a loco.

Just because they look the same, they aren't necessarily the same.

Even CD player motors aren't all the same voltage.

Keith,

 

I bought my CD-ROM motors from AliExpress in 2 batches, so I suppose I could have 2 different voltage variants. However, since they are all the 10mm thick type that might (?) limit the variability?

 

Out of my 2 batches, just this one motor is causing me an issue. If it is a lower voltage variant, I suppose putting a resistor in series should help. Or would a a diode to drop the voltage by ~0.5v be better?

 

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measuring the resistance (and telling us all) of several motors would help determine the best approach .... amazing how usefule a cheap multimeter can be 8-)

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3 hours ago, ISW said:

Keith,

 

 However, since they are all the 10mm thick type that might (?) limit the variability?

 

 

Have any got a Mabuchi label? (they AFAIK originated them)

If so, then one that I removed from a TT300 point motor was RF300C-11440 and is rated at 5.9v It's on the label. It's resisatance is approx 11.5ohms

 

See this one from Alibaba: PS1-motor.jpg

Another one from a DVD player is marked MDM3DL3CSF and is a the same resistance.

 

This other RF300C is however for 13v:

RF-300C-09550-D-V13-0-13V-DIY-motor-shaf

Edited by melmerby

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54 minutes ago, melmerby said:

Have any got a Mabuchi label? (they AFAIK originated them)

If so, then one that I removed from a TT300 point motor was RF300C-11440 and is rated at 5.9v It's on the label. It's resisatance is approx 11.5ohms

 

See this one from Alibaba: 

Another one from a DVD player is marked MDM3DL3CSF and is a the same resistance.

 

This other RF300C is however for 13v:

 

Keith,

 

You clearly know a lot more about these CD-ROM motors than myself. When I bought them, about 2-years ago, my only concern was the 10mm thickness. I didn't know there were variations ... :read:

 

Anyway, the ones I have are marked as below:

20191107_190353_resize.jpg.16daa0bb3cf9f993181f0cfa13f0521d.jpg

 

Can you 'translate' the marking into a voltage requirement? I'd be interested to know what I working with.

 

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9 hours ago, 34theletterbetweenB&D said:

Given that you know that a slow speed start is obtainable with BEMF not active, it is probably the BEMF constants that you want to access. These do not necessarily have addressable CV's provided, a search of the manual for the decoders you have is required (I have no relevant experience to offer for the products mentioned).

 

When I was having trouble with my decoders, I was given to understand that Gaugemaster decoders were rebadged(?) Digitrax items.  So I downloaded the Digitrax  manual   http://www.digitrax.com/static/apps/cms/media/documents/documentation/Decoder_Manual_V2-01_2014.pdf  Pages 46-49 describe adjusting motor control - somewhat difficult to follow I found - but I did make significant improvements with experimentation.  I repeat however that mine as DC 23s rather than 27s.

 

Might be worth a look.

Harold.

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20 minutes ago, HLT 0109 said:

 

When I was having trouble with my decoders, I was given to understand that Gaugemaster decoders were rebadged(?) Digitrax items.  So I downloaded the Digitrax  manual   http://www.digitrax.com/static/apps/cms/media/documents/documentation/Decoder_Manual_V2-01_2014.pdf  Pages 46-49 describe adjusting motor control - somewhat difficult to follow I found - but I did make significant improvements with experimentation.  I repeat however that mine as DC 23s rather than 27s.

 

Might be worth a look.

Harold.

Harold,

 

Thanks for that. I'll see if my decoder has the necessary CV54/55/56/57. Looks like a bit of a black art ...

 

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3 hours ago, ISW said:

Keith,

 

You clearly know a lot more about these CD-ROM motors than myself. When I bought them, about 2-years ago, my only concern was the 10mm thickness. I didn't know there were variations ... https://www.rmweb.co.uk/community/uploads/emoticons/default_read.gif

 

Anyway, the ones I have are marked as below:

https://www.rmweb.co.uk/community/uploads/monthly_2019_11/20191107_190353_resize.jpg.16daa0bb3cf9f993181f0cfa13f0521d.jpg

 

Can you 'translate' the marking into a voltage requirement? I'd be interested to know what I working with.

 

Not really, just what I have found on the internet and what I have from dismantled kit.

 

I couldn't find the one in your picture, It seems to be made by Minebea/Mitsumi but I cannot find a "MDN2" of that exact nomenclature anywhere,

The best I can find is this one: https://www.datasheet4u.com/datasheet-pdf/NMB-MAT/MDN2X/pdf.php?id=853290

(Which is only 2 or 5v rated!)

The "MDN3" one I have came out of a Panasonic DVD mechanism and like the the RF300 series motor is intended for 6 volts.

 

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Cut your losses and try here...

https://www.strathpefferjunction.com/shop/

He has all the variants covered including voltage dropper boards.

At least you can be sure which voltage motor you are getting along with all the fiddly bits for not a huge price.

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Looking on AliExpress I see cd-Rom motors from 1.5V to 9v which many rated at 5.9 

 

I wonder why the OP figures they would be compatible with a 12V system ? 

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33 minutes ago, Junctionmad said:

Looking on AliExpress I see cd-Rom motors from 1.5V to 9v which many rated at 5.9 

 

I wonder why the OP figures they would be compatible with a 12V system ? 

I can see you piont in relation to DC systems, but on DCC so long as you limit the voltage (through the CVs) this is not normally an issue.

 

I went down this route after watching a number of YouTube videos making the conversion. It seemed the best way to 'revive' my old Lima / Hornby locos with their ageing pancake motors, and this has been mostly successful. The CD-ROM motors came from a supplier linked in the videos.

 

Edited by ISW
Needed clarifying.

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