DIY DC Controller - any ideas

[bertiedog]

In the WW circuit , why is C2 so large ( in uF)?

 

Surely smoothing for a couple of 555's only needs to 220uF at most .

The supply to the motor is surely unsynchronised, chopped, rectified DC, a strange combination indeed.

 

The circuit from WW has not been published here so far, so I think that you are referring to the dual 555 PWM circuit, (totally un-related to the WW one). The 5000uf is simply smoothing in there, it is high, but decouples any ripples as far as I can see. The circuit was by Penfold in Bambini books. I have used the circuit several times and it works very well.

[bertiedog]

The copy of the circuit is from the book, I know I re-drew it several times, and I do remember a modification, but I have not got the notes either my own or from the Bambini book. I am pretty sure it worked though from the book, I used one for ages.

Anyway I am not using it again, the IC regulated PWM one from Shortliner's reference is far superior, especially as it is pretty fool proof on shorts etc., the regulator will shut down.

Stephen.

[bertiedog]

I would have to check the whole circuit's action , but as the power transistor takes the applied voltage from supply to near zero on each cycle, the lowering of voltage would make the 555's inoperative, but with the 5000uf it effectively un-couples the oscillators from the effects of the PWM output, as they can draw power from C2 on each cycle.

 

The top of each variable width square wave would have a ripple from the rectification, but it has no detrimental effect in practice, a perfect square wave is not needed, just the mean result.

 

Stephen.

[bertiedog]

Quick check, it is the power during each cycle for the 555 timers, without C2 they would shut down. The pictures separates the simple PWM parts from the output transistors which varies the fixed max to zero each cycle as defined by the 555 oscillators.

 

Stephen

 

[Tony_S]

I went through a phase years ago of building all sorts of controllers like some of the ones described in this thread. In the end I found the buzzing associated with the designs that I constructed so irritating I just used a simple design that just gave a nice clean DC. My DCC equipped locomotives ran nicely on this as well. In fact when I was first thinking about converting the layout to DCC I was concerned about whether the locomotives would continue to run as smoothly. They generally do (or better) but I now get irritated by the buzzy noise emanating from some of the decoders fitted in some "DCC fitted" models!

 

Tony

[bertiedog]

As I said all PWM can make noise, and it depends on the mechanism, a stiffer, tighter tolerance motor will be all right, but a Lima pancake will rattle like loose teeth. Coreless motors should work, but the coils generate a lot of back emf at a higher than applied voltage and can have arcing troubles on PWM across the brushes.

 

Better motors have potted windings, coated with resin, and these are OK, but cheaper motors do not, and the looser windings vibrate just like a loudspeaker. Can motors are generally quieter on PWM signals, the casing quietens it, whilst open frame are worse, and flat pancake the very worse.

 

With the simple 555 circuit, you can dampen the action with caps on the output transistors, or the feed to the base, this will distort the square wave but reduce the noise, but also lessen the control at crawl speeds.

 

Stephen.

[bertiedog]

So , with the circuit as drawn, what do you reckon the output waveform to the motor would look like on a scope.?

 

I would think its a 100Hz ( rectified 50Hz ) chopped off and on by a variable mark/space ratio ( depends on the pot setting) and at a variable frequency at a random position of the 100Hz cycle.

Correct or not.?

 

Yes, the timing of the pulses is down to the 555's, the bursts would have ripple, but it does not matter with motor control. In effect the 5000uf isolates the pulse circuit from the motor supply effects.

[shortliner]

For those who are interested in "DIY DC throttles" can I suggest a look here http://www.awrr.com/throttle.html

 

You will also find on that page something called "Not a throttle" which is an "output scaler", and acts something like a gearbox on a car, giving a large movement of the knob/handle with a small variation in speed at minimum setting. A similar device was offered in MRR for a fairly high price some years ago. If you do a lot of shunting/switching it may be useful to you. Have fun!

[bertiedog]

Useful collection, "The Throttle" looks interesting, as everything is adjustable. The ones based on the IC regulators are good, but up rate the regulators!, not worth saving a few pence.

 

 

The Scaler is interesting as it adds onto other controllers, scaling can be applied to most designs easily, switch in or out, it just spreads out the area the controller acts over.

 

The only nuisance of these US based circuits are the relays, they specify "Radio Shack" and these types are not easy to source here, you may have to find substitutes if you want the hand held units, although a cased unit can use direct switching reverse instead.

 

 

Stephen.

[Crosland]

Unfortunately as far as increasing the frequency of the PWM type, you can't do much, as above the lower frequencies of about 100 hz it becomes very audible, and would then need to jump to 20 khz to work without the sound generated.

 

PWM would work at 20khz, but only to adjust the range of speed around a value, control from zero to max impossible because of hysteresis in the magnetic field in the motor. It works with specialist coreless motors quite well for laboratory uses etc, and control equipment, but not models.

 

Stephen.

DCC decoders use PWM drive. Almost all modern ones use a high (inaudible) frequency and it works fine with ordinary motors. It is *required* for coreless motors which can very easily be damaged by low frequenct PWM.

 

Andrew Crosland

[bertiedog]

DCC decoders use PWM drive. Almost all modern ones use a high (inaudible) frequency and it works fine with ordinary motors. It is *required* for coreless motors which can very easily be damaged by low frequenct PWM.

 

Andrew Crosland

 

I trust you noticed I did not mention DCC, where the back EMF of coreless is dealt with by the Chip Circuit, (on suitable chips).

 

I was commenting on a PWM circuit delivering 12 volts PWM, a very different beast, which without clamping the back EMF, causes the arcing, and heating, that harms the commutators on coreless types.

 

Now.... a couple of more general points, back to the circuits being discussed,

 

 

In an ordinary motor the iron core damps the effect as it operates, and coreless means that, no iron core, so adding the bigger and finer coils they are efficient generators as well. The lack of a core also means heat builds up faster in coreless under high load, and PWM DC makes this worse.

 

PWM DC will work at high frequency with coreless if some protection is added to the circuit, and even at low frequency if fully clamped to remove the back EMF.

 

As mentioned before the Pentroller takes advantage of the back EMF, turning it from a problem into a feedback signal to modify the speed against load. DCC can do this as well, and requires the Cv to be matched to the motor in the same way the Pentroller requires it to be used with matched motor types.

 

The general purpose circuits here for DC do not need such a sophisticated approach, but also fall short of the Pentroller or the DCC control on offer from the model trade. Bear in mind that one chip can cost more than a complete home produced DC controller, and cannot match a computer DCC system costing many hundreds of pounds, which many people cannot possibly afford.

 

Personally I am not anti DCC I have a home made NMRA compatible controller that does the lot for the few chipped locos I have.

 

Stephen

[Penlan]

Off at an angle.....

 

Presumably these are panel mounted controllers, I have used a simple switch to change from panel mount to a hand held (HH).

 

The HH plugs into the Panel unit (or nearby), there's a changeover switch on the panel for Panel or HH. The HH has a 'pot' and a on/off switch only, no Transistor in the HH making the unit hot, the Changeover switch both on the panel and in the HH operates a DPDT relay in the panel unit.

 

The source of power for the HH on/off switch is the same + as goes to the 'pot'.

 

A diagram can be made available....

[jwd]

I'm surprised no one mentioned this one :

 

http://www.richardpr...s/DIYcont3a.pdf

 

seems to have everything, electronic overload protection, feedback, logarithmic speed control with inertia etc.

 

Also has a good write up and simpler controllers.

 

Anyone like to comment on it?

[Dukedog]

If you are looking for a simple DC controller that WORKS, then look at this.

 

This is one of the controllers I built using a circuit from "Model railway electrictronics" by Roger Amos.

 

I can't fault it, and the slow running is excellent for such a simple circuit. It will put a lot of PWM controllers to shame!

 

Cheers!

Frank

[Donw]

And a quick point...... often over looked .....is the type that progressively reduce the Pulses as the DC level increase only do this in the upper range by definition, ......do you always run your locos at top speeds????

 

 

If you have a vast layout with long drags, then a plain DC controller is frankly much better, no complexity at all, apart from possibly feedback.

 

Maybe the very best would have all these modes switchable !!!! but the most useful for most layouts is crawler speeds, (without too much noise).

 

Stephen.

 

It is really down to what your locos are like. I find with quality 0 gauge I get really good slow running with a simple emitter follower circuit. My experience with Triang as a boy was not the same!

PWM controllers will cause more motor heating. Each pulse applies full voltage but the back emf is lower therefore the current will be higher. The heat loss will be due to the current squared.

Don

[shrubpigsteven]

Hi, As a new member, I am getting to grips with this site, so here goes!

          I am taking 4mm scale outdoors and have had the layout running very well, with power from a 12v car battery, so as to get pure D.C. and to negate any issues with taking the mains outdoors. That all works fine, but I also would ask for any advise on what type of controller would be best for the spread of locomotives ( Hornby,Bachmann,Airfix and Heljan ) that I have, in order to obtain good slow speed control. My current controllers are 60 year old Bakelite Triang ones, that have a reistance mat inside and despite what you are thinking have done very well, if only to prove the possibilities.

          So, to polish off the job, I am torn between what's best and bad. The lin below takes me to something we all may find useful, but is it any better than the home made circuits suggested by one of the contributors, i.e. the circuit from Wireless World?

 

http://www.maplin.co.uk/panel-mounted-speed-regulator-module-30310

 

                                                                Regards  Steve Hollands.

[66C]

 

 

          So, to polish off the job, I am torn between what's best and bad. The lin below takes me to something we all may find useful, but is it any better than the home made circuits suggested by one of the contributors, i.e. the circuit from Wireless World?

 

http://www.maplin.co.uk/panel-mounted-speed-regulator-module-30310

 

Hi Steve

 

Beware of the Maplin panel mount unit - it has no short circuit protection. We (East Kilbride MRC) tried a couple of these a few years ago - they both failed after a few hours use and were returned for a full refund.

 

Regards.

[AMJ]

For garden operation you will probably be able to pick up an ex trainset unit for a few pounds on an auction site.  These are usually fed from a 16v AC supply but if you convert the electrics by by-passing the bridge rectifier and smoothing circuits you can then run it on a pure 12v DC.

 

One friend uses a cheap ex Thomas The Tank Engine controller for his layouts so don't dismiss anything.  This is a wireless controller with a base station so it might be ideal for conversion for use in the garden.

[sixteen 12by 10s]

If you are looking for a simple DC controller that WORKS, then look at this.

 

This is one of the controllers I built using a circuit from "Model railway electrictronics" by Roger Amos.

 

I can't fault it, and the slow running is excellent for such a simple circuit. It will put a lot of PWM controllers to shame!

 

Cheers!

Frank

I have to agree with Frank, i have used the same design as Franks for years on my big roundy roundy, and you get a quality controller for very little effort .

 

Gary

[DJfraz]

I personaly use the MERG kit speed controller.
I am not sure if it has the current output to run a Hornby dublo locomotive, but I have managed to run a triang princess from it with success. It provides a decent slow speed and can easily control a loco down to a crawl.

[ianb26]

I use a DIY circuit from Wireless World 1973, have built quite a few of these over the years. Fairly complex, but very good. My Wills J69, with a 5 pole motor and 60:1 gearing takes 30 minutes to traverse a 1/2 circle of Hornby track. My old Triang 0-6-0 chassis as built can been seen, with the body off, to show the motor "cogging" over between poles. I've scanned & rewritten the article to aid me to construct the units on a production (!) basis if you want a copy?

Hello there.

 

Just joined the forum, and saw this post. I would like a copy of this article, if it would be possible please. Do I need to give you my email address or would it be as a PM in the forum?

 

Thanks.

[stewartingram]

PM me you email addy I'll send it over.

 

Stewart

[Paul_sterling]

Afternoon Folks, 

 

Old thread though this is, and I apologise for digging it up, but its relevant to me query. My layout currently operates from an HM2000, which is generally fine for me barring two issues. 1 is, I would prefer a quieter transformer, the buzzing noise does my head in after a while, and 2nd, but a more significant issue is the high pitch whine generated when the locos are put under power by it that tends to cause me migraines. When the layout was at our old house, I even went to the degree of putting the controller in a drawer (with tea towels haha) so I couldn’t hear it.

 

I’m considering replacing the HM2000, and have been looking at the Gaugemaster units (I’m hoping to give them a call to discuss when the chance provides itself), but elimination of those two noise factors are important to me.

 

So I guess for me it is understanding what it is that the HM2000 has in it which is producing the high pitch noise (the transformer one is fair enough, and making the transformer remote could be an answer), and is this a fundamental part of that particular control method?

 

P.S. Sorry for the garbled info, I’m a mechanical engineer rather than electrical, so my electronics knowledge is limited (colour-blind, so they wouldn’t let me near it!).

 

Thanks, Paul.

 

[mikesndbs]

14 minutes ago, Paul_sterling said:

Afternoon Folks, 

 

Old thread though this is, and I apologise for digging it up, but its relevant to me query. My layout currently operates from an HM2000, which is generally fine for me barring two issues. 1 is, I would prefer a quieter transformer, the buzzing noise does my head in after a while, and 2nd, but a more significant issue is the high pitch whine generated when the locos are put under power by it that tends to cause me migraines. When the layout was at our old house, I even went to the degree of putting the controller in a drawer (with tea towels haha) so I couldn’t hear it.

 

I’m considering replacing the HM2000, and have been looking at the Gaugemaster units (I’m hoping to give them a call to discuss when the chance provides itself), but elimination of those two noise factors are important to me.

 

So I guess for me it is understanding what it is that the HM2000 has in it which is producing the high pitch noise (the transformer one is fair enough, and making the transformer remote could be an answer), and is this a fundamental part of that particular control method?

 

P.S. Sorry for the garbled info, I’m a mechanical engineer rather than electrical, so my electronics knowledge is limited (colour-blind, so they wouldn’t let me near it!).

 

Thanks, Paul.

 

 

 

Hi Paul

 

The HM2000 uses PWM, i'e variable width full voltage pulses to control the speed of the motors. Generally this is one of the better controllers using this method.

Personally I don't like it due to motor heating and noise.

The Gaugemaster basic range, Combi, Walkabout, D and so on use full wave rectified transistor controlled output at 100Hz, there will be some very minimal buzz at motor start on some motors but you get really good smooth running.

 

Another controller you might like to consider is the Morley Vector Crawler, this is twin track control, with either the supplied handheld units on 2.5 M wires or unit control knobs, plus a built in CDU for point motors.

 

If I were buying a new controller this is what I'd opt for due to the flexibility.

 

If you are interested in the more technical side of it and or comparisons between a GM and older Morley Vector zero 2 then check out my playlist.

There is even a DIY option.

 

Controllers and more

 

Hope this helps?  

Edited November 6, 2019 by mikesndbs

[Paul_sterling]

Hi Mike,

 

Yes that is most helpful thank you.

 

Re. the Morley units, i've not heard of them before, are they comparable in quality to the Gaugemaster Units? I must admit, the inclusion/possibility of fly-leads is profoundly helpful. which method of control does it use? as per HM2000 or the Gaugemaster D?

 

Thanks, Paul.