Cheap controller - your views?

[Trevor James]

While looking at YouTube films on model railways I came across this one https://youtu.be/T64lhCwN9Ws from Budget Model Railways in which they promote a very cheap controller for which they make a 3D printed housing. Does anyone with knowledge of electrics and 009 loco's have an opinion as to whether this controller is a good idea?

[Graeme Dunbar]

An interesting link Trevor, and plenty more where it came from - Budget Model Railways: https://plus.google.com/u/0/+BudgetModelRailways

In principle the controller, or something similar built from what is available at the time on ebay should work. Some caution may be prudent as there are a couple of things at least that might cause problems. The first is the PWM frequency and if that is too low then it may cause overheating in some models and the second is current limiting (or lack of) in the case of shorts or overloads.

Given the subject of the website/channel a budget controller for a budget model railway is an excellent idea.

This looks like the controller: https://www.ebay.co.uk/itm/DC-6V-28V-3A-PWM-DC-Motor-Speed-Controller-Forward-Reverse-Control-With-Switch/272667994451?hash=item3f7c476953:g:~TYAAOSwuMZZB~qJ:rk:7:pf:0


The PWM frequency is not given and the current is quoted as 3 A max so a fuse might be a good addition.

[clayliner]

Thanks for posting the link, Trevor - very interesting. The controller is a quarter of the price of the much-acclaimed Minitrains one but I wonder if there's much difference inside the box? While it appeared to work fine with the models he demonstrated I wonder if it will suit our little motors equally well?

Further comments from those with electronic know-how are awaited...

David.

[rod335]

If it is a PWM (Pulse width modulation) controller it will be of no use for locos with coreless motors (e.g. Bachmann Baldwin). The slow-running characteristics will be nil and the controller will be a waste of time and money, possibly causing extensive damage to the motors. The Minitrains controller is also a PWM unit and will not work satisfactorily with coreless motors. I know it has been said many times before but just stick with Gaugemaster.

[Graeme Dunbar]

I've been digging around and another possible "quirk" more than serious problem occurred to me. Some cheap PWM controllers do not cover the full range of output voltages from 0% to 100% of the supply. Not reaching fully on is no major problem here, but not being able to reduced the speed to fully off may be. Some modern models will creep along at very low voltages.

Another listing for what appears to be the same speed controller:  https://www.ebay.co.uk/itm/DC-6V-28V-3A-PWM-DC-Motor-Speed-Controller-Forward-Reverse-Control-With-Switch/272667994451?hash=item3f7c476953:g:~TYAAOSwuMZZB~qJ:rk:7:pf:0   states 5% - 100%. This might be enough to make a loco with good motor crawl.

Another listing states the board includes a 3 A fuse: https://www.ebay.co.uk/itm/6V-12V-24V-28V-3A-80W-DC-Motor-Speed-Controller-PWM-Speed-Adjustable-Revers-SS/322817966741?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D52543%26meid%3Dbe33798924de4c23a98bb97e295aee2c%26pid%3D100005%26rk%3D5%26rkt%3D12%26sd%3D272667994451%26itm%3D322817966741&_trksid=p2047675.c100005.m1851


It is not obvious on the board (i.e. I've not spotted it). It could be a resettable "polyfuse" I suppose, but a smaller value would be better for 009 locos.

[Graeme Dunbar]

If it is a PWM (Pulse width modulation) controller it will be of no use for locos with coreless motors (e.g. Bachmann Baldwin). The slow-running characteristics will be nil and the controller will be a waste of time and money, possibly causing extensive damage to the motors. The Minitrains controller is also a PWM unit and will not work satisfactorily with coreless motors. I know it has been said many times before but just stick with Gaugemaster.

I'll have to disagree with Rod here. I think he is making too much of a generalisation. Coreless motors work perfectly well with (the right) PWM controller. Low frequency PWM and the sort of pulsed controllers that use the rectification of the mains can cause problems of overheating. PWM can give excellent slow speed regulation (see DCC decoders which are all PWM). The problem can occur with some old (or old design) feedback controllers where the feedback sensing was not designed with coreless motors in mind.

Even low frequency PWM (of the right kind in the right environment) need not burn out motors. I made a little T-gauge demo. The video is rather old and the jitter is due to the camera and the compresssion needed at the time to post on YouTube.
https://www.youtube.com/watch?v=kw8SCKRFH_U

[WALLSHIRTS]

The few that I have won't go down to zero volts. I have a Grafar 08 that won't stop on these controllers. Seems OK for iron core motors like Mashima though. I'm also getting sparks when a wheel back shorts out on a point blade.
Mal.

[rod335]

Sorry Graeme, you cannot have tried a Minitrains controller with a Bachmann Baldwin. Even on the lowest setting the loco leaps off like a scalded cat. The same loco on a Combi is perfectly controllable. At an exhibition a couple of years ago I was next to Richard Holder and on Sunday afternoon we ran some of my locos on his Wantage layout. Perfect on his Combi, decidedly jerky and noisy on his Pentroller. Everyone else who I know agrees that coreless motors do not like either feedback or pulse power of any sort. I do not know the technical reason why, nor, indeed, wish to. But it is nonetheless true.

[Graeme Dunbar]

Rod - whatever the Minitrains controller does to a Bachmann Baldwin cannot be extrapolated to PWM in general and all locomotives with coreless motors. (I did say "the right" PWM controller.)

I don't know what the circuit for the Minitrains controller is, but I suspect it is optimised for use with their locos with flywheels in them and so just maybe uses low frequency pulses.

In this thread we are talking about a generic PWM electronic speed controller from ebay and not what what some model train controller manufacturers may choose to call PWM. One ebay speed controller similar to the one linked to quoted 20 kHz frequency, which should be high enough for most coreless motors.

[rod335]

I did not intend my comments to be restricted purely to the Minitrains controller. It is my experience that ALL pulse power controllers of any sort do not work well with coreless motors. I do not, and indeed do not wish to, know why. But I know it to be true. Same with feedback. Since the much loved Gaugemaster stuff works equally well with both coreless and conventional motors and it seems apparent to me that coreless motors are going to be used increasingly, it seems a bit pointless to adopt a control system that is incapable of operating both types of motor satisfactorily. But you pays your money and you takes your choice.

[Graeme Dunbar]

I should have checked the Minitrains web site - they say the PWM frequency is 16.625 kHz, not quite the "silent drive" of high frequency PWM in DCC decoders as people below a certain age should hear it.  http://www.minitrains.eu/mt-acc.html but certainly not low frequency as I thought it might be.

[Frank]

As far as I know, all DCC and radio control systems use PWM control as it is the only way to get power control into a very small package.  These seem to work OK with coreless motors though. 

I think the frequency of the PWM will be important here and the DCC and Radio Control ones are likely to be high frequency whereas the older design mains driven track controllers are more likely to be mains frequency or similar, ie very low frequency.

It is true though that some of the cheaper PWM controllers do not cut the power completely and so this could cause problems.   Any system with full two way control (ie forward and reverse on the same knob, rather than speed control and separate direction switching) is likely to have a true zero power position between the forward and reverse settings.   Some of the cheap controllers on ebay etc. are motor speed controllers not loco controllers and are designed to give speeds from slow to fast but not to give an off position.

Frank

[B.Meldon]

I think there is a fundamental problem regarding controllers for 009.

Put simply because of the wide variety of motors used in 009 locos no one controller is ideal for all.

A controller that will work well with a loco with a modern coreless motor may not work well at all with an old Arnold chassis.
A controller that works well with an old Arnold chassis may not work well at all with a loco with a modern coreless motor.

The solution is simple, stick to one type of motor in all your locos and then have a controller that works well with them.
My problem is in common with most 009 modellers I have a wide range of types of motors in my locos!

I have a layout that has a simple 9v AC transformer, a bridge rectifier, an old H&M thermal cut out, a centre off direction switch and a very nice wire wound 500ohm 5 amp rated rheostat with a completely isolated section at its lower end of travel. This is as

[Hugh Norwood]

Well...
No I'm not going to say anything...

[Alan Feldon]

Oh go on Hugh !

There was a discussion on NGRM regarding these as a result of which I bought two from China for about a fiver each .I must admit I have only used them on two isolated lines on my layout (the main part all ready having quality controllers ) and these with  limited use so far seem fine with Kato tram chassis with good control .
At least if they do burn out motors ,it won't cost me much to replace kato chassis !