74009 Posted February 28, 2021 Share Posted February 28, 2021 Hi all, I've been experimenting with reviving a few older models that have ringfield motors using the motors from CD / DVD drives. Results have been very good indeed, with very smooth, controllable operation and plenty of power. I've got some multiple unit kits that I built years ago so this is a good way of markedly improving their performance without wholesale re-engineering. Many of these motors are designed for 9v or even 6v - so for use under plain DC I added a suitable resistor. My question is this - when a DCC chip is controlling a motor's speed, does it do so by varying the output voltage, or does it always supply nominally 12v but 'chopped' into a part-wave? Or are there chips of either type? I'm thinking that in the former case I can probably adjust CV settings so that the maximum voltage supplied is 6v or 9v as appropriate - but in the latter case I'd probably still need to add a resistor. Thanks and best regards Stuart Link to post Share on other sites More sharing options...
WIMorrison Posted February 28, 2021 Share Posted February 28, 2021 If you use Zimo Decoders then you can adjust CV57 to limit the maximum voltage that the Decoder outputs 1 2 Link to post Share on other sites More sharing options...
Nigelcliffe Posted February 28, 2021 Share Posted February 28, 2021 In just about all cases, the decoder will be outputting full voltage, but using the PWM cycles to reduce the average voltage. There are multiple settings which produce the PWM cycle seen, both CV settings, and the throttle speed sent to the decoder. The PWM will be at high frequency, typically above 10kHz, and optionally up to 40kHz in some decoders. For an iron cored motor, this will be seen as an average voltage. For a very low inertia motor, this might produce a problem with constant changes in speed as the duty cycle goes on/off. However, experience of small low-voltage coreless motors used by 2mm scratchbuilders for many decades with high frequency PWM control in both DC and DCC suggests its not a real issue. I'm aware of 2mm finescale models with nominally 3v motors running for extended periods without issue on nominally 12v DC controllers, and some of my own models have nominally 8v motors, run originally on DC and latterly on DCC without issue. So, my expectation is that it is not an issue, just adjust the decoder settings. Decoders such as Zimo which have an independent "voltage" setting means you're not restricting the speed steps available which can happen if just using CV2+CV5 to control the "start" and "max" volts. - Nigel 1 1 Link to post Share on other sites More sharing options...
74009 Posted February 28, 2021 Author Share Posted February 28, 2021 Hi Iain / Nigel, Thank you very much - that's all most helpful. Best regards Stuart Link to post Share on other sites More sharing options...
TWG Posted March 1, 2021 Share Posted March 1, 2021 There are decoders designed for 6 volt motors, such as the CT Elektronik DCX65 and the Doehler & Haass PD06. 1 1 Link to post Share on other sites More sharing options...
74009 Posted March 5, 2021 Author Share Posted March 5, 2021 Thanks TWG - that's something I didn't know and very useful. Best regards Stuart Link to post Share on other sites More sharing options...
RAF96 Posted March 5, 2021 Share Posted March 5, 2021 (edited) Standard DCC motor output is 0 to12v Dc PWM Cv5 can be used on many decoders to limit V- max, but needs Cv6 to be adjusted to match - V-mid. Edit - diode packs can be used to knock down the output voltage to suit the motor voltage. Edited May 18, 2021 by RAF96 Link to post Share on other sites More sharing options...
74009 Posted April 22, 2021 Author Share Posted April 22, 2021 Hi all, Thank you for your help with this. In the end I tried some Zimo MX600R decoders, with CV57 adjusted appropriately. CV57 needs to be set to 10x the required max voltage - so for a 6 volt motor, CV57 = 60. The results have been astonishingly good - slow speed running is amazing and it's hard to believe that it's just a standard Hornby or Lima 'pancake' drive chain, fitted with a new motor costing around £1.50. This has certainly removed the need to re-engineer all the multiple unit kits I built in the 1980s / 90s. Best regards Stuart 4 Link to post Share on other sites More sharing options...
Esmedune Posted May 17, 2021 Share Posted May 17, 2021 How about getting a 12V motor??? https://www.ebay.co.uk/itm/174302469026 Link to post Share on other sites More sharing options...
ISW Posted May 18, 2021 Share Posted May 18, 2021 16 hours ago, Esmedune said: How about getting a 12V motor??? https://www.ebay.co.uk/itm/174302469026 Just be careful of the 'thickness' of the CD-motor. If you are re-motoring a 3-axle bogie, you'll need a CD-motor that's about 10mm thick to ensure it's clear of the centre wheelset. Ian 1 Link to post Share on other sites More sharing options...
RAF96 Posted May 19, 2021 Share Posted May 19, 2021 Not only motor thickness - but some ring-field housings have an intrusion for the intermediate gear axle which precludes fitting a CD type motor. Link to post Share on other sites More sharing options...
74009 Posted May 25, 2021 Author Share Posted May 25, 2021 It might work as long as the thickness isn't too great. I notice in the spec that at 12v it turns at 14195rpm, so that would make for an extremely fast running locomotive. The two types of 6v motor I've used so far have top speeds of 5,500rpm and 8,100rpm, and fitted into a Hornby ringfield I estimate their scale top speeds to be around 80mph / 120mph. So it's possible that this 12v motor would produce a top speed in the 200mph range; although of course in DCC the top speed could be limited. Stuart Link to post Share on other sites More sharing options...
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