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Dan6470

DIY DC Controller - any ideas

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Hi,

 

I'm in the process of planning my model Railway, OO gauge. The railway will be composed of a Junction and Terminus stations with goods yard and loco sheds. Presently, I'm only interested in using conventional DC for control of the locos. A fair proportion of the locos are Hornby Dublo, so I would anticipate a need for more/greater current to run these old locos. I would like to build my own controllers and ask if you have built your own controllers whether you would be willing to share your experience in this regard.

 

From the research that I have done, it would seem that the better/best controllers use various forms of pulse power in order to achieve slow running but I am aware that this can cause over heating and noise. I had initially thought of using an unsmoothed, full wave rectified wave form to trigger the pulses which I think should produce 100Hz but is this reasonable or should I use a much higher frequency to reduce motor noise? 20khz comes to mind;) Also, since it is almost inevitable that a short circuit will occur at some point, then of course I need to plan some sort of protection circuit for current limiting into the controller.

 

I also propose to integrate negative feedback into the controller whereby the back emf of the motor can be sampled and used to maintain a constant speed. As mentioned a number of the locos are Hornby Dublo, so perhaps not the best valve gear, and my layout will have some gradients. So I think I will find Negative feedback invaluable.

 

There are a number of books available for model railway electronics but the problem here is that there is no feedback from the readers that indicate whether a circuit is good, bad or simply unusable. So any pointers you can give would be most appreciated.

 

Dan

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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?

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Dan

 

You may want to look here for some controller ideas (and plenty of other info to distract you!):

 

http://home.cogeco.c...rcuitIndex.html

 

But to answer your question - I built this a few years ago:

 

http://users.rcn.com...tcl/ccartcl.htm

 

which ticks most of your boxes and was used extensively on an American HO modular club layout, hence had to cope with a wide variety of mechanisms - old and new.

 

The only changes I made were to the momentum resistor values (as suggested in the text) as we found for our purposes there was too much delay/momentum; you could practically go off and make a cup of tea

before some locos really got going! Hence suggest fine tuning values to suit. Controller worked well and has now been passed on as we graduated to DCC....

 

John

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There are lots of suitable designs on the net, but as you say how do you know what they really do?

 

 

I know, as an electrical engineer, but even then the circuits may not work as expected, so it needs recommendation, and the best course is to join the MERG group, who are a club, shop, group of enthusiasts etc, and have the experience to say what works and what does not.

 

Your requirement is for control of older "type" motors, none the worst for that, straight DC, with feedback may be the best, with variable pulse available in a switchable form. It would be the same for an all Mashima fleet, they just have lower draw on current.

 

Feedback works where a fleet are basically the same motors, otherwise it has got to be in some way adjustable. Double motored locos cause problems with feedback and don't work with the set-up.

 

The best control for low speeds are variable mark space CV (constant voltage) controllers, but if the motors are 3 pole and 5 pole on the same layout there may be differences, and such controllers are able to make the motors hum due to the pulses.

 

The next best are feedback controllers, which can be CV mark space types or pure DC, or a mixture, a circuit that senses the load and back EMF, trying to maintain a constant current drain, again when pulses are used the motor may hum at low speeds.

 

But after all the extras are removed a pure DC supply is able to run any type of motor without hum, and straight forward variable voltage regulator chips, which have built in overload protection are the best all rounder.

 

Commercial designs try to deal with as many variables as possible, so building your own can fine tune to what you have much better. It is also very inexpensive,... £10 would build a comprehensive spec., controller, with the exception of the transformer for power, the most expensive item.

 

hope this helps,

 

Stephen.

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Dan

 

You may want to look here for some controller ideas (and plenty of other info to distract you!):

 

http://home.cogeco.c...rcuitIndex.html

 

But to answer your question - I built this a few years ago:

 

http://users.rcn.com...tcl/ccartcl.htm

 

which ticks most of your boxes and was used extensively on an American HO modular club layout, hence had to cope with a wide variety of mechanisms - old and new.

 

The only changes I made were to the momentum resistor values (as suggested in the text) as we found for our purposes there was too much delay/momentum; you could practically go off and make a cup of tea

before some locos really got going! Hence suggest fine tuning values to suit. Controller worked well and has now been passed on as we graduated to DCC....

 

John

 

The circuit is fairly straightforward, although for non electronics builders a bit short of some basics like the power connections to it! ..you have to assume a lot, .......also the UK 50 hz mains frequency difference from 60hz in the States may explain the slower responses to the commands, meaning lower some of the trimming values ,as you found, to compensate.

 

All parts are available easily and not costly, although the reversing relay adds a bit. Substitute transistors,(properly chosen), would work, nothing is too critical.

 

It would be a very good general purpose circuit, and removes most risk from pulses noise and potential heating effects.

 

Stephen.

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You can build this one yourself, or buy it ready-made through ebay ( I chose the second route) - and I highly recommend it - an excellent device for DC control which will be used on the Harlem layout

 

http://www3.sympatic...pleton3/851.HTM

 

A Full PWM type circuit, (Constant voltage), very interesting, I use Mr Penfolds version, (in Bambini books on the 555) with 555's generating the pulses, resulting in exactly the same square wave forms.

 

This type works very well indeed for control. especially shunting, but as the other postings on the US design for variable voltage with pulse say, it can over heat the motors, but only under load on long runs on the main lines, light load, and short runs no issue. Crawl control cannot be bettered with PWM, no way any other circuit can be superior, but only at these low speeds.

 

 

Such PWM controllers can make some motors hum and noisy, again it varies, well set up motors do not mind, but add loose bearings, and dry gears, and you have noise, add tight gears, resilient mounts, and grease lube, no issue.

 

My own mods to the 555 driven type of PWM are to raise the frequency and use capacitors to smooth the output, which are switchable to suit different motors, this also reduces potential motor heating as the RMS value of the output is lowered.

 

Motor heating is not serious on PWM as such, it is after all nothing to do with applied voltage, it is the average current drawn under load, less efficiency, that is the heat source, not the higher voltage pulses, as nothing is applied at all in the gaps!!

 

But yes, under load the magnetic field behaves dynamically, and despite all theory, the motors heats up more on square wave pulses, than plain DC. The motor operates on the average of the pulses, but the mean value is not linear as the load increases and more inefficiency occurs...result heat. The back EMF is also high with pulses, and contribute to the heating, as with coreless motors, which should not be used on PWM, they can burn out in extreme load conditions,.

 

Coreless are often driven by PWM signals in electronic equipment, but are in constant known load limits, and are quite safe then.

 

Therefore PWM CV type controller...perfect for micro layouts and switching layouts...not for large club layouts with legions of locos of different types.

Stephen.

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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?

 

Have you the circuit to post here, bearing in mind the authors copyright, or it could be posted to Photobucket etc., and referenced.

 

Stephen.

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You can build this one yourself, or buy it ready-made through ebay ( I chose the second route) - and I highly recommend it - an excellent device for DC control which will be used on the Harlem layout

 

http://www3.sympatic...pleton3/851.HTM

 

I have breadboarded the design this afternoon, and it all works fine, although the diagram shows the transistor as normal, it is a Darlington pair type, and any rated above the specified would do, it is the gain they are after here.

 

Also I used the higher rated regulator, why down rate for a few pence. No fuse is needed, it's self regulated, but I would add LEDs to show AC power in and DC out.

 

 

It works with 5 pole motors very well, it does make a three pole a touch noisy, but very controllable. For coreless near useless, it could be tamed, but why bother there are better plain DC controllers for these.

 

I will transfer to a PC pad board and re-test, perfect for the new Shortline I am building.

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Hi all, Sorry for the delay in responding to your posts but nevertheless I do thank you for the time and trouble you have gone to in answering my questions.

 

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?

 

Hi Stewart, 30 mins for 180° sounds good, I would love to see the schematics/article if you can post it or even pm me the details.

 

 

 

Dan

 

You may want to look here for some controller ideas (and plenty of other info to distract you!):

 

http://home.cogeco.c...rcuitIndex.html

 

But to answer your question - I built this a few years ago:

 

http://users.rcn.com...tcl/ccartcl.htm

 

which ticks most of your boxes and was used extensively on an American HO modular club layout, hence had to cope with a wide variety of mechanisms - old and new.

 

The only changes I made were to the momentum resistor values (as suggested in the text) as we found for our purposes there was too much delay/momentum; you could practically go off and make a cup of tea

before some locos really got going! Hence suggest fine tuning values to suit. Controller worked well and has now been passed on as we graduated to DCC....

 

John

 

Hi John, thanks for the your post and links. Through the research that I have undertaken I am familiar with the circuits of Rob Paisley, by that I mean that I have come across them, and as you say it is quite easy to get distracted when you start to look at his ideas.

 

The TechTronics circuit is also quite interesting. Simple in its operation, it would seem that the control is just through the manipulation of the amplitude of the 120Hz, or in our case 100Hz, rectified waveform. Does it have any overload protection? I can see that D4 provides current limiting but I’m not sure if this would be faster enough in case of a short circuit. How have you found this in practice? Also, since my proposed layout will have some gradients, I would like a controller that can maintain a constant speed and I assume that this would have to be through some form of feedback. Perhaps this could be added to the circuit, it’s certainly food for thought. Thanks very much.

 

 

There are lots of suitable designs on the net, but as you say how do you know what they really do?

 

 

I know, as an electrical engineer, but even then the circuits may not work as expected, so it needs recommendation, and the best course is to join the MERG group, who are a club, shop, group of enthusiasts etc, and have the experience to say what works and what does not.

 

Your requirement is for control of older "type" motors, none the worst for that, straight DC, with feedback may be the best, with variable pulse available in a switchable form. It would be the same for an all Mashima fleet, they just have lower draw on current.

 

Feedback works where a fleet are basically the same motors, otherwise it has got to be in some way adjustable. Double motored locos cause problems with feedback and don't work with the set-up.

 

The best control for low speeds are variable mark space CV (constant voltage) controllers, but if the motors are 3 pole and 5 pole on the same layout there may be differences, and such controllers are able to make the motors hum due to the pulses.

 

The next best are feedback controllers, which can be CV mark space types or pure DC, or a mixture, a circuit that senses the load and back EMF, trying to maintain a constant current drain, again when pulses are used the motor may hum at low speeds.

 

But after all the extras are removed a pure DC supply is able to run any type of motor without hum, and straight forward variable voltage regulator chips, which have built in overload protection are the best all rounder.

 

Commercial designs try to deal with as many variables as possible, so building your own can fine tune to what you have much better. It is also very inexpensive,... £10 would build a comprehensive spec., controller, with the exception of the transformer for power, the most expensive item.

 

hope this helps,

 

Stephen.

 

Hi Stephen, thank you for your post. I haven’t come across any double motor locos but would assume the same problem in double headers. You mention the variable mark space CV (constant voltage) controllers causing hum but, may be a stupid question, can’t this be resolved by using a higher frequency for pulses, as mentioned in my original post, 20khz or above?

 

 

 

You can build this one yourself, or buy it ready-made through ebay ( I chose the second route) - and I highly recommend it - an excellent device for DC control which will be used on the Harlem layout

 

http://www3.sympatic...pleton3/851.HTM

Thank you Jack, the PWM walk around throttle is interesting. It would seem that PWM lends itself to slow running which is one of my criteria but I have to try and eliminate the hum that Stephen mentions. Once again thanks for your post.

 

 

 

A Full PWM type circuit, (Constant voltage), very interesting, I use Mr Penfolds version, (in Bambini books on the 555) with 555's generating the pulses, resulting in exactly the same square wave forms.

 

This type works very well indeed for control. especially shunting, but as the other postings on the US design for variable voltage with pulse say, it can over heat the motors, but only under load on long runs on the main lines, light load, and short runs no issue. Crawl control cannot be bettered with PWM, no way any other circuit can be superior, but only at these low speeds.

 

 

Such PWM controllers can make some motors hum and noisy, again it varies, well set up motors do not mind, but add loose bearings, and dry gears, and you have noise, add tight gears, resilient mounts, and grease lube, no issue.

 

My own mods to the 555 driven type of PWM are to raise the frequency and use capacitors to smooth the output, which are switchable to suit different motors, this also reduces potential motor heating as the RMS value of the output is lowered.

 

Motor heating is not serious on PWM as such, it is after all nothing to do with applied voltage, it is the average current drawn under load, less efficiency, that is the heat source, not the higher voltage pulses, as nothing is applied at all in the gaps!!

 

But yes, under load the magnetic field behaves dynamically, and despite all theory, the motors heats up more on square wave pulses, than plain DC. The motor operates on the average of the pulses, but the mean value is not linear as the load increases and more inefficiency occurs...result heat. The back EMF is also high with pulses, and contribute to the heating, as with coreless motors, which should not be used on PWM, they can burn out in extreme load conditions,.

 

Coreless are often driven by PWM signals in electronic equipment, but are in constant known load limits, and are quite safe then.

 

Therefore PWM CV type controller...perfect for micro layouts and switching layouts...not for large club layouts with legions of locos of different types.

Stephen.

 

Hello again Stephen, you mention using a 555, I assume 555 timer. How far have you increased the frequency? Is a practical to go to 20Khz with a model railway throttle? Your last comment here “Therefore PWM CV type controller...perfect for micro layouts and switching layouts...not for large club layouts with legions of locos of different types†perhaps there’s a way around this problem with a switch that will switch out the PWM circuit and revert to a DC throttle. Thing is, I’m totally in the dark here. I recognise that I’ve got to do some experimenting here but I would much prefer to be lazy and be spoon fed. No, it’s not that I’m a Yorkshire man ... we're just tight careful;)

 

 

 

Dan

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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.

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I am interested in the Wireless World and will arrange a copy, without seeing it I would assume PWM in base, as no other way gives such control. Feedback can help slow speed, but most aim at constant speed for gradients, Codar used to make one, and I have the circuit stored, but it is not wonderful on crawl. It was an early user of momentum effects.

It would be fine for larger layouts.

 

All feedback controllers are lost with multiple motors, banking, US units in tandem or more, the intermittent contact that must occur despite all efforts to keep everything spotless and all wheel contact, will lead to lurches as the tiniest feedback signal is used to correct what has not happened.

 

Now I hear the man at the back saying he uses feedback with multiple motors, and in real life the makers of the units add hysteresis to the circuit, sudden changes do not cause sudden jumps, but some locos may still be sensitive and react, and the choice of the lag is critical, too much damping, and you might as well have no feedback.

 

Personally I do not like feedback where there is a large amount of different locos to run, as they all behave differently, only slight, but it is there......and my feeling is that you are the driver, and should be in control on gradients anyway!!.......

 

To get the best of both ways, do not modify one type or the other, just have both and switch in as needed, A regulator based 0 to 12vdc, with pure DC(handles anything in sound order)., a PWM for shunting, and maybe a feedback type for mainline loop running on a big layout.................or buy DCC...........trouble is the word BUY...............DCC is very pricey indeed, as all three circuits coud be built for about the cost of a single Lenz decoder.

 

Also as before, join MERG it is the source of a lot of help, and masses of experience, although prepare to have your arm twisted towards the dark side, DCC.........there are those in there who still resist it though.

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From memory - I don't have the circuit in front of me, and I'm trying to sort out a PC problem (read one message in Outlook and it freezes, needs CTRL/ALT/DEL to stop it then restart, worse problem than the old RMWeb!) - I believe the circuit to be a PWM with adjustable feedback. Based on the then new drill speed controllers. Has the option of adding accelaration and decceleration. Built in overload protection (simple bulb). For my uses I've "designed" (if thats the word) a veroboard layout, with a handheld contoller box (speed control, direction switch) coupled to a fixed main unit (the majority of the circuit). Components such as transistors are dated, but modern equivalents are available. I've plenty of stocks so haven't needed to source new. There is a 2nd potentiometer, mounted on the main unit, which the article describes as a "max speed" setting, but I find it better to fine tune the "min speed" setting with this. Seems to work ok over a range of motors, though the pedantic might adjust it with every different motor! To be honest I'm not up to speed with the latest types available, I've found this one suited my needs for all these years, if it ain't broke don't fix it, so I've not bothered to look elsewhere. You're welcome to a copy of my notes, if it suits you, fine, if not, well nothing lost.

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I am interested in the Wireless World and will arrange a copy, without seeing it I would assume PWM in base, as no other way gives such control. Feedback can help slow speed, but most aim at constant speed for gradients, Codar used to make one, and I have the circuit stored, but it is not wonderful on crawl. It was an early user of momentum effects.

It would be fine for larger layouts.

 

All feedback controllers are lost with multiple motors, banking, US units in tandem or more, the intermittent contact that must occur despite all efforts to keep everything spotless and all wheel contact, will lead to lurches as the tiniest feedback signal is used to correct what has not happened.

 

Now I hear the man at the back saying he uses feedback with multiple motors, and in real life the makers of the units add hysteresis to the circuit, sudden changes do not cause sudden jumps, but some locos may still be sensitive and react, and the choice of the lag is critical, too much damping, and you might as well have no feedback.

 

Personally I do not like feedback where there is a large amount of different locos to run, as they all behave differently, only slight, but it is there......and my feeling is that you are the driver, and should be in control on gradients anyway!!.......

 

To get the best of both ways, do not modify one type or the other, just have both and switch in as needed, A regulator based 0 to 12vdc, with pure DC(handles anything in sound order)., a PWM for shunting, and maybe a feedback type for mainline loop running on a big layout.................or buy DCC...........trouble is the word BUY...............DCC is very pricey indeed, as all three circuits coud be built for about the cost of a single Lenz decoder.

 

Also as before, join MERG it is the source of a lot of help, and masses of experience, although prepare to have your arm twisted towards the dark side, DCC.........there are those in there who still resist it though.

 

Hi Stephen, I appreciate what your saying, very difficult to find one controller that can do everything but maybe, just maybe, the following link may prove interesting.

 

http://www.freepaten...com/3994237.pdf

 

It's based around a saw tooth waveform with pulses superimposed on it and as the saw tooth waveform increases towards maximum output the pulses are switched off. I'm not too sure at what Frequency the pulses are, produced by a multi vibrator and are adjustable via a variable resistor, but it looks interesting and incorporates a feedback circuit for continuous output and an overload protection circuit. So ticks all the right boxes.

 

Have a look and see what you think.

 

Dan

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From memory - I don't have the circuit in front of me, and I'm trying to sort out a PC problem (read one message in Outlook and it freezes, needs CTRL/ALT/DEL to stop it then restart, worse problem than the old RMWeb!) - I believe the circuit to be a PWM with adjustable feedback. Based on the then new drill speed controllers. Has the option of adding accelaration and decceleration. Built in overload protection (simple bulb). For my uses I've "designed" (if thats the word) a veroboard layout, with a handheld contoller box (speed control, direction switch) coupled to a fixed main unit (the majority of the circuit). Components such as transistors are dated, but modern equivalents are available. I've plenty of stocks so haven't needed to source new. There is a 2nd potentiometer, mounted on the main unit, which the article describes as a "max speed" setting, but I find it better to fine tune the "min speed" setting with this. Seems to work ok over a range of motors, though the pedantic might adjust it with every different motor! To be honest I'm not up to speed with the latest types available, I've found this one suited my needs for all these years, if it ain't broke don't fix it, so I've not bothered to look elsewhere. You're welcome to a copy of my notes, if it suits you, fine, if not, well nothing lost.

 

Hi Stewart, No hurry at this end, still redecorating the "Railway Room". Then I've got to build the baseboards, build the track, lay the track and ballast before I get anywhere near the electrics. So no sweat, sort you PC out then I'll be very happy to see your controller.

 

Dan

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It action is similar to commercial designs like ECM , the feedback is current sensing, not back EMF type, I would not say it is advanced over other circuits these days.

 

 

A chip regulator could be driven like this, and there are variants that use discrete components, but it depends a lot on exact uses and I would not bother with the complexity of the patent spec version.

 

Decent running is far more to do with the loco, not the controller, it is not a cure for a bad mechanism.

PS I do seem to remember the WW version, but no copy of that date to hand, so will need the text etc. I think the Codar may have used the design.

Stephen.

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If you have good quality mechs then a emitter follower type works well. You can use an op-amp at the front. If you mechs are sticky the pulse type can work well but there is always the odd motor that doesn't seem to like it. Also if start to add better motors such as coreless portescaps these can be subject to brush wear as the motor sees the supply as stop/start pulses. That why Stuart Hine developed the Pentroller. The design used a sample and hold circuit tomeasure that back EMF and used that compared to the controller setting to adjust the output voltage.

Donw

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The Stewart Hine Pentroller mentioned is a full back EMF sensing unit with pulses at a higher frequency, mainly developed for small 2mm and finescale 4mm models, and it not really suited to older high current motors. It can work easily with coreless types.

 

Another published controller for home build in the Basin Street design via MERG in PDF form, free to everybody, a pulse and variable output up to pure DC that can handle higher ampages easily.

 

After all of this one should bear in mind once moving, little difference will be detected between each type, or a battery!! It is the start and low speed that makes the difference, and more down to the quality of the mechanism than the controller.

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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?

 

Is this the one titled "better control for small dc motors" or similar? It has two variable resistors one for speed and the other for feedback and uses a 12V car bulb in series with the motor as an overload protection device.

If it is I have also used it in the past (I'm DCC now) I even adapted it for a computer controlled model railway using a BBC micro, pre DCC

 

It is very good at maintaining speed under varying conditions of load and gradient although I have heard it can cause pitting of the motor commutator due the high instantaneous current applied in the on period. 12V is always applied to the motor but the duty cycle is reduced for low speeds.

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You can build this one yourself, or buy it ready-made through ebay ( I chose the second route) - and I highly recommend it - an excellent device for DC control which will be used on the Harlem layout

 

http://www3.sympatic...pleton3/851.HTM

 

 

HI..

 

I use the 3 AMP unit with walk-a-round memory. http://www3.sympatico.ca/kstapleton3/821.HTM Best controller I ever brought, I like the way you can build the hand peice to have brake/mermentum but the best part is when you are shunting you can be pushing a van to it's spot, change direction on the controller but it wont change untill you stop.

 

Stuart in OZ

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It sounds like the WW controller was PWM, with an increasing level of DC as the speed increases, this is the typical way they operate. This type uses the load to assess the current supplied, just like a regulator chip.

 

 

Only a full PWM with dormant parts of the waveform can check the back EMF to use as feedback control, although I have seen circuits set to function with a core DC level as well.

 

This is the PWM circuit based on 555 timers, not as sophisticated as the one Shortliner introduced, no momentum setting, although it could be added.

 

post-6750-127266389387_thumb.jpg

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Is this the one titled "better control for small dc motors" or similar? It has two variable resistors one for speed and the other for feedback and uses a 12V car bulb in series with the motor as an overload protection device.

If it is I have also used it in the past (I'm DCC now) I even adapted it for a computer controlled model railway using a BBC micro, pre DCC

 

It is very good at maintaining speed under varying conditions of load and gradient although I have heard it can cause pitting of the motor commutator due the high instantaneous current applied in the on period. 12V is always applied to the motor but the duty cycle is reduced for low speeds.

 

Yes that's the one. I've built up to a dozen of them over the years, still use my original "bodge" trial version now and again!

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It sounds like the WW controller was PWM, with an increasing level of DC as the speed increases, this is the typical way they operate. This type uses the load to assess the current supplied, just like a regulator chip.

 

 

 

 

I built the WW controller. As you say the design was such that as the throttle was turned up the base voltage increased until the pulses disapeared and you got pure DC.

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The WW version makes the reference to the patent type unnecessary, as the patent one has curiosities in it , and for actual ease of building a proven published one will be better, even an older design, all components are available, or better alternatives made to substitute, like power transistors that used to cost pounds and now cost pence!!

 

For instance virtually any older circuit with the 2N3055 as output can have TWO in parallel to halve the heat, the plastic versions are so cheap now!!

 

Stephen.

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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.

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