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Very Poor Low Speed DCC Control of CD-ROM Motors

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23 minutes ago, RAF96 said:

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.

Thanks very much for that link. Never thought that a UK supplier would be available for such things, as so never searched previously. They nicely clarify that 12mm motors are okay for twin-axle motors, but 10mm motors are needed for 3-axle motors (to ensure clearance to the centre axle). I'd been under the mistaken impression that 10mm was necessary for all. I'm still learning ... :read:. Mind you, when I did fit a 10mm motor to a 3-axle bogie the clearance was very small. I had to grind some metal off the motor housing to get a suitable clearance.

 

What the link also explains is that putting diodes in the motor circuit is a suitable method of reducing the voltage (my understanding is that a single diode drop it by ~0.6V). I'v got a few diodes, taken out of old Triang-Hornby Class 25s, so I'll be giving that a try. 

 

Thanks again for the link / info.

 

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12 hours ago, melmerby said:

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.

 

Keith,

 

Searching for these motors is much simplified now thanks to your information. Once I use "RF-300" or "RF-400" as the search criteria, I find plenty to browse through.

 

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1 hour ago, ISW said:

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.

 

If you use Zimo decoders then you can use CV57 to reduce the output Voltage and you won’t need to touch any of the other speed related CVs 

  • Agree 1

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2 hours 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 ? 

These are the design voltage and a 5.9v motor should be OK on DC & DCC as long as it isn't driven flat out all day long.

 

You can get 13v ones which would be ideal:

https://www.aliexpress.com/item/32948084853.html

$2.18 each but these are 12mm ones

Edited by melmerby

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I would have thought the CD/HD drive motors are brushless, and I thought some decoder/motor combinations can be trouble some with brushless motors.........just a thought.

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These are not drive motors but tray motors, the drive motors are completely different and are multipole brushless motors.

N.B. Brushless motors cannot be used on DCC (or even DC) as they require a dedicated driver to provide the various phases to control the speed (they are AC motors with a DC driver board).

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18 minutes ago, boxbrownie said:

I would have thought the CD/HD drive motors are brushless, and I thought some decoder/motor combinations can be trouble some with brushless motors.........just a thought.

 

I think you are confusion brushless motors with coreless motors. DCC decoders cannot drive brushless motors.

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17 minutes ago, Bedlington North said:

 

I think you are confusion brushless motors with coreless motors. DCC decoders cannot drive brushless motors.

I knew there’d be trouble with them :lol:

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It seems I might have found the culprit to my original problem of 'jump start' on a CD-ROM motor with a Hattons MD4 4-function DCC decoder. I unplugged the headlights (blue/white and blue/yellow wires) and, lo, the problem went way ...

 

The lights in question were the original incandescent 12v ones fitted by Mainline to my class 56. I had assumed that, being 12v DC bulbs, these would be entirely suitable to DCC. My error it seems. I'll be retrofitting them with LEDs (with appropriate resistor in series!).

 

All very odd.

 

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A decent decoder will support bulbs for loco headlights - any of the mainstream European and US brands describe such setups in their manuals. 

 

 

As for brushless motors, they are supported in quite a few DCC decoders:  Marklin's Sinus motors are brushless, and numerous European decoder makers include versions or settings to suit those locos. 

 

- Nigel

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2 hours ago, Nigelcliffe said:

 

 

 

As for brushless motors, they are supported in quite a few DCC decoders:  Marklin's Sinus motors are brushless, and numerous European decoder makers include versions or settings to suit those locos. 

 

- Nigel

How do they provide the different phases at frequencies from 0Hz upwards?

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I have read on many places including this one

https://sites.google.com/site/markgurries/home/technical-discussions/decoder-motor-drive

 

that the decoder output voltage to the motor remains the same level & the speed is controlled by the pulse duration

 

but this may also need to be read

 

https://sites.google.com/site/markgurries/home/technical-discussions/decoder-motor-drive/pwm-motor-drive

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@Sol

 

Not quite correct, especially for Zimo ;)

 

1782085275_Annotation2019-11-08211614.png.bcd4d742b1bcd77dc2069d9e068c4ca1.png

 

As you can see some decoders support you changing the actual voltage supplied to the motor ;)

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Thanks Iain - learn something new each day in this hobby.

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18 hours ago, ISW said:

It seems I might have found the culprit to my original problem of 'jump start' on a CD-ROM motor with a Hattons MD4 4-function DCC decoder. I unplugged the headlights (blue/white and blue/yellow wires) and, lo, the problem went way ...

 

The lights in question were the original incandescent 12v ones fitted by Mainline to my class 56. I had assumed that, being 12v DC bulbs, these would be entirely suitable to DCC. My error it seems. I'll be retrofitting them with LEDs (with appropriate resistor in series!).

 

All very odd.

 

 

The decoder may have recognised the heavier current draw from the headlights and assumed the loco had an ancient iron core motor or something....? 

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56 minutes ago, 298 said:

 

The decoder may have recognised the heavier current draw from the headlights and assumed the loco had an ancient iron core motor or something....? 

 

That's a thought. I've replaced the bulbs with LEDs (with resistor) and added a small (12-ohm) resistor to the motor circuit and now the motor starts without 'jumping'. It's still less smooth than other locos I've converted in the same manner, so I'll see if a different decoder (same model) will help.

 

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