Electronic Boosters

[roger440]

About 25 years ago i too got fed up with my 08 stalling at low speed. I ended up putting a new motor and gear set in it with a bigish flywheel and very low gearing The transformation was marked. Very pleased i was too. A few accidents occured to with ramming stationary stock, especially as i used to operate with an HM walkabout with the inertia function. It certainly didn't stop quickly!

 

You might not have space for a flywheel with the existing motor/drive, but if you change it, im sure you can find the space.

[kevinlms]

I still cannot see why the circuit would need to determine (and cater for) the range of speeds at drop out.

 

We are talking about a very short duration and a preset mid-range speed - 6v would be adequate. The actual visible change in speed of the loco would be almost imperceptible and even a minute lurch or slowing would be far preferable than the dead stop that is observed now.

 

Hi Kenton

 

Having read through this section, I can see why you would think that such a solution ought to be 'simple'. In practice it is very difficult to acheive what you are asking.

You are asking for a circuit to 'know' when power has been lost and immediately supply power from an alternative source. By its nature it has to be very fast acting & automatic and needs to be built into the loco.

 

There are 3 ways to acheive this.

 

1/ Mechanical - probably using flywheels. While they do work, they have to be set up properly as others have described.

2/ On board batteries - so you can't lose power. There is/was? a system called Red Arrow, I think.

3/ Use DCC with new chips that incorporate 'No Stall' technology. - This seems to be the best approach, because it is currently being supplied by different manufacturers, so there are many heads working at it.

You're looking for a way to do this without a sophisticated means of communicating to the motor, such as what is incorporated in a DCC system.

 

I think that while your aims are good, it is a bit like asking for perpetual motion, it cannot exist.

However, don't let anyone here stop you looking for such a design. I'm sure that many will buy it off you & throw away their expensive DCC systems, once proven and available for less than the price of a basic DCC system.

 

Kevin Martin

[AMJ]

On the mechanical side wasn't there a maker that used to produce a flywheel system that had a clutch so that the motor was not connected to the flywheel/drive when power was off. The loco then coasted to a halt. One year there was a stand at York show you could stop the loco quicker by reversing the power. No good for a small loco.

 

For a small 4 wheel loco might need to fit electrical gear into a wagon if space is limited, but in doing so I'd fit pickups to feed the loco. Or how about just a shunters wagon with extra pickups?

[34theletterbetweenB&D]

A version was sold as the Dynadrive system, don't know if there were any similar competitors.

[spamcan61]

 

2/ On board batteries - so you can't lose power. There is/was? a system called Red Arrow, I think.

 

Kevin Martin

 

Thanks! I meant to mention that technology back at the start of the thread, but couldn't recall the name. Not much info. around these days but found this:-

 

http://www.newrailwaymodellers.co.uk/electronics-infra-red-control.htm

 

I always liked the concept, no more track cleaning :-), an up to date version using lithium battery technology and wireless would be cool, although probably still difficult to physically fit in some 4mm locos.

[Kenton]

3/ Use DCC with new chips that incorporate 'No Stall' technology. - This seems to be the best approach, because it is currently being supplied by different manufacturers, so there are many heads working at it.

You're looking for a way to do this without a sophisticated means of communicating to the motor, such as what is incorporated in a DCC system.

If you already subscribe to the DCC religion then the solution is obvious and you can see no point in seeking an alternative, and every reason to generate more conversions to the flock.

 

This is not all about how it can, already is done, with DCC.

This is not about offering the conversion route to DC users as the true way to salvation.

 

It is simply about pondering if it is technically possible.

 

The theory is clear - it is not about running continuously on batteries or about re-engineering the motor or the track or reinventing the wheel.

 

I just get the feeling that some here are approaching the idea from the "I've been converted to DCC" stance or are missing the point by going down a mechanical rather than electrical solution.

 

The cost is really an irrelevancy as no doubt if that was the only thing considered when innovating to DCC we would not have that option now.

 

Anyway could some one explain (simply) how the Lenz DCC system actually works - there are no batteries - so how can it keep the motor turning when there is no power. I'm guessing it is detecting the lost signal component not the lost power, but without the power source how does it work?

[Jol Wilkinson]

Kenton,

 

clearly some DCC afficinados are true evagelists and can see no need for any other solution .

 

As a kit builder, I try to make my models as mechanically smooth running as possible. Combined with compensation or springing, handbuilt P4 trackwork and good DC controllers, I don't seen benefits from DCC that would would outweigh the disdvantages it would create on my layout.

 

However, DCC may offer advantages to the modeller that buys his RTR locos of the shelf and runs it on (indifferent) Ready To Lay trackwork. DCC seems capable of overcoming some degree of poor mechanical and electrical performance, obviating the need to make mechanisms, etc. more efficient. Hence it is a quick and trendy solution, albeit rather expensive.

 

Personally, I think that the initial objective should always be to have efficient and smooth running mechanisms, effective pickup, good track and consistent wheel/track standards as a basis. If you don't have those, then you are always chasing your tail looking for good performance. Any other technical improvement is then a bonus.

 

Jol

[kevinlms]

If you already subscribe to the DCC religion then the solution is obvious and you can see no point in seeking an alternative, and every reason to generate more conversions to the flock.

 

This is not all about how it can, already is done, with DCC.

This is not about offering the conversion route to DC users as the true way to salvation.

 

It is simply about pondering if it is technically possible.

 

The theory is clear - it is not about running continuously on batteries or about re-engineering the motor or the track or reinventing the wheel.

 

I just get the feeling that some here are approaching the idea from the "I've been converted to DCC" stance or are missing the point by going down a mechanical rather than electrical solution.

 

The cost is really an irrelevancy as no doubt if that was the only thing considered when innovating to DCC we would not have that option now.

 

Anyway could some one explain (simply) how the Lenz DCC system actually works - there are no batteries - so how can it keep the motor turning when there is no power. I'm guessing it is detecting the lost signal component not the lost power, but without the power source how does it work?

 

Its not about 'blocking any alternatives to DCC' at all - what would be the point of that?

 

You say the theory is clear - well I don't disagree with your statement at all, have I said otherwise? However, putting it in practice is something quite different. I don't think a non-DCC solution is as easy as what you think it ought to be. Where do you propose this power is to come from?

 

 

I know of 2 ways of storing electricity (well small amounts at least), batteries or capacitors. So if there is no battery, then a capacitor is supplying the power.

 

Here is an example showing how it is wired.

http://members.optus...north/alive.htm

 

As you can see the capacitor is located after the rectifier and any processing, but before the motor/light control. So if the pickup system fails, the model takes its power from the capacitor.

 

For your proposal to work, you would need to replicate this, but without using DCC.

 

I also agree with you that cost isn't the issue (any technology is usually expensive for the first one, but becomes much cheaper as more people work out ways of making it), but I differ in thinking that something obvious is out there.

The fact is, its not just about controlling model trains, but there is a huge industrial market out there for a product that would simply enable an electric motor to run at a controlled speed without some form of processing, which is exactly what DCC is.

 

 

 

FWIW, I don't personally actually have a DCC system, primarily because I don't have a layout. However, I have been involved with a number of conventional DC layouts large & small and have no further ambition to wire up complex layouts the traditional way. DCC is far more flexible and as others have said, the same loco runs smoother & slower than ever thought possible.

 

 

 

A friend who knows nothing about layout wiring, has recently converted his layout to DCC and reckons its the best thing his done. He still knows nothing about wiring, but he just dials up his train and off he goes.

 

He also ran a sound loco (actually a DMU) on DC and thought that was good. Now he has the full range of sounds that weren't available before.

 

 

I do realise that your mind is made up Kenton, and nothing is going to convince you otherwise, but increasingly people that were against DCC (usually on cost grounds) are changing and would never go back. I would also agree with those that have existing DC layouts that DCC might not be for them, but new construction - absolutely.

 

I reckon, its like broadband internet, having used it would you go back to dial up? I think not.

 

 

Please pursue your non-mechanical, non-battery, non-DCC method of keeping trains running when they lose power. I'm sure there is an answer out there, but I don't know what it is.

 

 

Kevin Martin

[Kenton]

I know of 2 ways of storing electricity (well small amounts at least), batteries or capacitors. So if there is no battery, then a capacitor is supplying the power.

It has been made perfectly clear that an onboard battery is being suggested to provide the temporary (very short duration) pulse to the motor at a fixed voltage (say 3-6v). The capacitor storage has been ruled out as stated above due to its size and the polarity requirement.

 

FWIW, I don't personally actually have a DCC system, primarily because I don't have a layout. However, I have been involved with a number of conventional DC layouts large & small and have no further ambition to wire up complex layouts the traditional way. DCC is far more flexible and as others have said, the same loco runs smoother & slower than ever thought possible.

Well I have both DC and DCC layouts and have wired and rewired several for DC in the past (though this is not a wiring debate just an operational one)

 

My experience is that DCC has much to offer on large layouts - multiple locos being the definition of "large", but has very little to offer the one/two loco layout other that a massive increase in controller cost and loco cost.

I, like many, have no interest in flashing lights on my loco or the, what I consider, the abomination of sound.

My experience with DCC is that it really simplifies about everything concerning multiple loco operation (eg a small layout TMD) but does nothing or very little to aid the loco running ability.

 

I do realise that your mind is made up Kenton, and nothing is going to convince you otherwise, but increasingly people that were against DCC (usually on cost grounds) are changing and would never go back.

So this has nothing to do with me ignoring DCC. I use it and am relatively happy with it. But I still think DC is perfectly useable and taking that step to DCC is not required on some layouts. Even though I have 2 controllers a basic Dynamis Wireless and a Prodigy Express and have a few locos chipped, these are not always useable on every layout.

 

Besides this is still not the point of the exercise, which remains firmly in a solution to the problem without imposing DCC.

... and I didn't want this to get into the never ending debate about DCC or DC - as stated in the OP.

[kevinlms]

 

 

Besides this is still not the point of the exercise, which remains firmly in a solution to the problem without imposing DCC.

... and I didn't want this to get into the never ending debate about DCC or DC - as stated in the OP.

 

True, but if you read the other thread referred to earlier, there is a sample circuit (fag packet) of what is required to design such a solution without using DCC (see around post 42 I think).

 

Now look at that and tell me that having gone to all that trouble, you may have well gone DCC and gained the other benifits.

 

Perhaps you have other ideas of where this power is coming from (battery you now state) and how would you control it? That is a valid question, as its easy to say stick a battery in to power it across the dead spot. Remember, there is a world market outside model railways for this.

 

 

Kevin Martin

[Dagworth]

Something like this ought to be possible.

The power first hits a relay coil of a latching relay which will determine polarity and therefore direction required. The main power is then rectified and charges a small capacitor. The relay contacts are arranged as a reversor so that the power hits the motor in the correct direction. In normal operation the track voltage will be higher than that allowed through the transistor from the battery so the diode above the transistor will be reverse biased and no power will flow from the battery. Cut track power and the battery/transistor is now at a higher voltage and current will flow through the motor from the battery. As the charge in the capacitor drains through the transistor the motor will slow to a stop until track power is regained and the cap recharged.

The diode in the main flow line at the top is to prevent the battery from charging the cap.

 

Andi

[bertiedog]

Kenton, I thought I had explained the way the DCC "no stall" works, the circuit charges a very large value capacitor from the chip, which takes the power from the DCC signal, Even standing still the capacitor is charged from the standing voltage.,

 

As the loco moves the DCC signal is maintaining the speed, when a break in the signal occurs the circuit senses the loss and then operates from the capacitor as a substitute for the missing power, holding the control and power at the level it failed at till it returns.

 

To stretch the very tiny amount of power, about 2volts x 500ma or about a watt, the power is applied as very short duration pluses, with no voltage, then a pulse and so on, which multiplies what power s available by about 10 to 20 times, (very variable due to various loads, type of motor and speed).

 

A voltage doubling circuit is used, like a switched power supply, to get the max voltage up to about 8 volts, at the expense of even lower current, but as the motor is already turning, these pulses will keep it moving, even at the very low current.

 

At very low speed and therefore a low load on the motor, the loco will run for several seconds at a steady speed, overcoming the dirt, insulated frogs, or even pieces of paper laid on the track.

 

This circuit is not part of DCC , it was a by product of the pulse stream control that DCC uses, and could easily be duplicated with a non DCC on board processor.

 

But after designing, programming and building the circuit, all you end up with is the Lenz chip running on DC, so the use of DCC is cheaper and available now.

 

It would be very interesting to get a DC version of the "no Stall", I am told that Lenz did make such a prototype, but never put it into production. The main problem is that the power to charge the capacitor is not there until DC is applied to get the loco to run, unlike DCC where the charging occurs as soon as the Loco is in contact with the standing voltage on the track.

 

You could get the situation with a DC version that the "no stall" is required as the loco moves off from zero, when the load on the motor is high, and taking all the available power, at this point the capacitor is still trying to charge and will not be able to maintain the motion.

 

With DCC no problem exists the "no Stall" is there right from the start,and cuts in at all speeds and loads, although there is a caveat not often mentioned with Lenz's circuit, that it does not operate well at higher speeds, where the poorer operation is covered up by the inertia of the loco.

 

It mainly works best at low speeds, and trains with light loads, no A4 with 12 coaches!!!, works fine with an 060 and a few trucks. Don't forget, most of the time you are completely unaware anything is happening, it just keeps moving under control.

 

None of this is trying to sell DCC, I do not use it much, but have some US locos that came fitted as standard, therefore got a controller to run them. All my scale locos are DC, usually with flywheels, so If I wanted "No Stall" , adding a chip is practical and the cheapest way.

There are other solutions, you could take the power with you on board, Ni-Mh cells, for instance and simply run radio control,, a total answer to bad track, or even no track!!!........RC equipment is made in micro sizes these days, and you get the same control as DC, but the batteries will need charging etc.

 

It would be feasible to charge them from,the track having a standing voltage on it, but we are coming is a circle here and the idea is beginning to sound like DCC

 

I simply do not think an analogue approach with relays etc., will work in practical terms, the relays draw extra power to work, and the complexity would be mind-boggling to get it to work at the range of zero to max speed and forward and reverse. The loco would need a higher voltage battery, and the relays would have to be sensitive reed types, and another issue occurs, they will be near each other physically and have to be magnetically shielded.

 

Also the latch to un-latched time would be a problem, the relays would not respond fast enough, the magnetic field takes time to collapse and re-establish.

.

I could envisage an O gauge demonstrator being built to show a relay based solution, it needs that sort of space to work, and get the batteries in. The motor would have to have a big flywheel to overcome the tiny glitches from the relays cutting in and out.

 

I am not un-experienced with relays, I worked for GPO Telephones on Strowger and reed relay equipment for many years, and a relay based solution would work, in a rather cruder than electronic form.

 

Again a analogue DC transistor circuit could be devised to cut in the power when needed, but that's the difficult stumbling block, WHEN,..... it needs "intelligence logic" to control the circuit as to when to work, and at what power level, it is not a simple as it seems, as the voltage is variable when the loss occurs as well as the load current.

 

A steady running loco on a circle of track, at a fixed voltage and speed, would be easy to control on the loss of power, inertia, and hysteresis would cover up any lurch or glitch, but on a real layout it simply is too complex.

Again I must repeat, I am not supporting or promoting or selling DCC, just saying the answer to stalling is already there in the DCC system, you could equip the loco at once, given the cost of course.

 

These comments are general to the issue, just overall thoughts, and are meant to point out how difficult the problem is unless DCC is used..

 

Stephen.

[Guest baldrick25]

Something like this ought to be possible.

The power first hits a relay coil of a latching relay which will determine polarity and therefore direction required. The main power is then rectified and charges a small capacitor. The relay contacts are arranged as a reversor so that the power hits the motor in the correct direction. In normal operation the track voltage will be higher than that allowed through the transistor from the battery so the diode above the transistor will be reverse biased and no power will flow from the battery. Cut track power and the battery/transistor is now at a higher voltage and current will flow through the motor from the battery. As the charge in the capacitor drains through the transistor the motor will slow to a stop until track power is regained and the cap recharged.

The diode in the main flow line at the top is to prevent the battery from charging the cap.

 

Andi

What happens to the loco when the power controller is moved to zero , as happens when stopping at signals, or stations?

My guess the loco ignores that action , switches the 9V battery into circuit and powers away with no control.

Alternatively the reversing relay coil has no voltage across it, so the contacts drop to the de-energised position, the loco , now battery powered , reverses and ramps off backwards at speed.

[Dagworth]

What happens to the loco when the power controller is moved to zero , as happens when stopping at signals, or stations?

My guess the loco ignores that action , switches the 9V battery into circuit and powers away with no control.

If the power is reduced normally then the cap will discharge as the voltage reduces so the loco will stop. I'd imagine the discharge time only needs to be a few seconds say 2 or 3. It only needs to hold charge long enough to get over dirt.

 

Andi

[bertiedog]

Something like this ought to be possible.

The power first hits a relay coil of a latching relay which will determine polarity and therefore direction required. The main power is then rectified and charges a small capacitor. The relay contacts are arranged as a reversor so that the power hits the motor in the correct direction. In normal operation the track voltage will be higher than that allowed through the transistor from the battery so the diode above the transistor will be reverse biased and no power will flow from the battery. Cut track power and the battery/transistor is now at a higher voltage and current will flow through the motor from the battery. As the charge in the capacitor drains through the transistor the motor will slow to a stop until track power is regained and the cap recharged.

The diode in the main flow line at the top is to prevent the battery from charging the cap.

 

Andi

 

This could work.......with constant load, no real operating voltage range etc, it would work fine with say a loco on a demonstration track, with a tested and known current drain, etc, but not in a real world situation with actual working conditions....and it might need an O gauge loco to get the relays etc in the space,

[Dagworth]

This could work.......with constant load, no real operating voltage range etc, it would work fine with say a loco on a demonstration track, with a tested and known current drain, etc, but not in a real world situation with actual working conditions....and it might need an O gauge loco to get the relays etc in the space,

 

Voltage range is covered by the cap charging from the track voltage, as the transistor is driven from the cap it can only allow as much voltage from the battery as is supplied by the track. The battery is a pp3, which will fit in pretty much any OO gauge mainline loco, and the relay can be a tiny device, see http://uk.rs-online.com/web/c/?sra=oss&searchTerm=latching+relay

 

I could build this to fit in any Lima mainline loco.

 

Andi

[kevinlms]

Voltage range is covered by the cap charging from the track voltage, as the transistor is driven from the cap it can only allow as much voltage from the battery as is supplied by the track. The battery is a pp3, which will fit in pretty much any OO gauge mainline loco, and the relay can be a tiny device, see http://uk.rs-online....=latching+relay

 

I could build this to fit in any Lima mainline loco.

 

Andi

 

Agreed, that such a circuit could possibly be built in an empty box such has a typical old Lima pancake motor drive model. But the OP request was for a 2 axle loco, one that according to later statements was too small for the 'complexity' of a flywheel drive. It doesn't suggest that a lot of space is available.

 

Kevin Martin

[Kenton]

Perhaps you have other ideas of where this power is coming from (battery you now state) and how would you control it?

Not just stating now but all the way back in post #1, I suggested the battery as the backup source

[bertiedog]

Trouble is the variables, 0 volts to start, the speed dependant not only on voltage but the load, as the voltage increases, yes, the motor goes faster, but on the break, which could be from a micro second to several seconds, the cap discharges and controls the power from the battery, but at what pace? It would have to be trimmed to suit the various loads, voltages and current, one capacitor discharge rate value can't cater for all situations.

 

What happens if the power is reversed when the loss occurs, the loco is proceeding forward under battery power, and then gets a reverse voltage, not impossible as the operator may seee the problem and reverse the power, it is no worse than a sudden reversal, but the speed it results in is a bit unpredictable.

 

Simply turning off the power trips it, yes for only a few moments, but again variable dependant on what level the power is cut at, and what current is being drawn due to load. All in all a lot of variables to cater for, and it's all covered with the Lenz chip.

 

Stephen.

[Kenton]

Kenton, I thought I had explained the way the DCC "no stall" works, the circuit charges a very large value capacitor from the chip, which takes the power from the DCC signal, Even standing still the capacitor is charged from the standing voltage.,

Thanks again for explaining re-explaining the operation of the DCC version.

I still do not fully understand though why a "very large value" capacitor can be used in the DCC version but is "too big" for a DC version. I do understand with DC that using a cap alone to discharge over the short duration "dead spot" is not possible due to polarity issues and the power requirement - but surely the DCC version would have the same problem. Similarly I can see the use of a cap to drive the "keep alive" circuitry (built in the DCC chip) but cannot see how the power is sourced.

[kevinlms]

Not just stating now but all the way back in post #1, I suggested the battery as the backup source

 

OK, its a confusing thread as almost all the discussion was about capacitors. However, a battery is less flexible than a capacitor, in that care has to be taken to recharge it, whereas you could use a capacitor with diode protection.

 

But as someone has suggested about your original post, what are you doing with a 4 wheel loco on insulfrog points? There are better ways of dealing with this problem in that case.

 

 

Kevin Martin

[Kenton]

Something like this ought to be possible.

Andi, thanks for the positive input.

That is more along the lines I was thinking - though more technical than I could suggest.

I was thinking that the pulse duration of the transistor switch would be determined by some simple timer triggered by the loss of voltage (cap) and the sensing done by some solid state chip/relay combination.

 

The fact that the circuit would still cut in even when the loco is desired to halt (station/stop signal) really does not matter as the duration would only be, I believe, hardly be determinable < sec.

 

My musing OP was not being specific to any precise loco just the typical example of a 0-4-0 that encounters the problem of a dead frog on an standard Peco insulfrog type point. We all know the type, little Harry's train set with Thomas the Tank, or any number of equivalents. Something along the lines of ... if there is space to fit a decoder then there may be space to fit a solid state/small circuit board. solution to the DC problem. The only real limit to space is that some of us were going off at a tangent to discuss a mechanical solution.

 

Something like this ought to be possible.

Andi, thanks for the positive input.

That is more along the lines I was thinking - though more technical than I could suggest.

I was thinking that the pulse duration of the transistor switch would be determined by some simple timer triggered by the loss of voltage (cap) and the sensing done by some solid state chip/relay combination.

 

The fact that the circuit would still cut in even when the loco is desired to halt (station/stop signal) really does not matter as the duration would only be, I believe, hardly be determinable < sec.

 

My musing OP was not being specific to any precise loco just the typical example of a 0-4-0 that encounters the problem of a dead frog on an standard Peco insulfrog type point. We all know the type, little Harry's train set with Thomas the Tank, or any number of equivalents. Something along the lines of ... if there is space to fit a decoder then there may be space to fit a solid state/small circuit board. solution to the DC problem. The only real limit to space is that some of us were going off at a tangent to discuss a mechanical solution.

[bertiedog]

The capacitor problem is dealt with in two ways, the absolutely huge value, (in several FARADS) means the device has a very low voltage rating, 1.2volts to 2.5 volts or so, dependant to brand. So although it is storing "Power", up to a couple or so watts, say,, it is in a form that will not run a motor which in the Lenz circuit, applies a max of 8 volts when the no stall cuts in. The current available is very low, only a few milliamps, but they then use a very neat trick...............

 

The tiny voltage is applied to an oscillator that converts it to high frequency AC, and then this AC voltage is raised to the higher level the motor needs, by using a circuit rather like a switched power supply., it is outputted in tiny DC bursts to stretch the available power out for a few moments.

 

They use the DCC signal in a modified form, making each digital control pulse as short as possible, just enough to make the motor turn at the specified rate the DCC signal has set. The speed remains the same, along with the direction, at the level last set before the stall condition.

 

The motor is already moving, so the string of pulses at low current will just about keep things moving till power returns, but only just,it needs the inertia of the motor to do this trick, and believe me, it is a trick!!!

 

A big powerful loco will last a few moments, a coreless light weight motor will run for up to 30 seconds on the power from the capacitor.

 

At first glance it seems a battery would be better than a capacitor, but they are much larger, need time to charge and discharge,(capacitors are near instant in this use), and batteries wear out, which the caps do not in practical terms.

 

Also suggestions of using a latching relay was made, but the cost is as much as the the DCC chip!, they are expensive devices.

 

Stephen.

[Kenton]

What happens if the power is reversed when the loss occurs, the loco is proceeding forward under battery power, and then gets a reverse voltage, not impossible as the operator may seee the problem and reverse the power, it is no worse than a sudden reversal, but the speed it results in is a bit unpredictable.

The power reversal is a good point though as I said above the speed/load is irrelevant - it does not matter if the loco travels at a lower or higher speed during this very small duration - just that it travels.

 

The power reversal could conceivably occur during this very small duration though I would guess on most standard DC controllers this would be difficult to practically achieve. But concede that there may well be a requirement to protect the switching transistor/components to protect from the short.

[Dagworth]

The power reversal is a good point though as I said above the speed/load is irrelevant - it does not matter if the loco travels at a lower or higher speed during this very small duration - just that it travels.

 

The power reversal could conceivably occur during this very small duration though I would guess on most standard DC controllers this would be difficult to practically achieve. But concede that there may well be a requirement to protect the switching transistor/components to protect from the short.

Power reversal is simply covered by my circuit. The first thing the power hits is the coil of a latching relay, which controls the polarity of power fed to the motor. Reversal of the polarity on the track will throw the relay, the power to the motor is then reversed to match the track polarity.

 

All the electronics in my circuit are after the bridge rectifier and before the relay contacts. No damage can possibly occur to the electronics from polarity reversal on the track. You could put the thing on AC and apart from the relay buzzing the loco would proceed in the last direction it was told to when it was on DC.

 

Basically what my circuit does is to put a power source and a controller inside the loco, which takes its direction instructions from the track polarity and its speed output from the track voltage. The way it is arranged means that it only actually has any effect in the short period after the track voltage is cut suddenly to zero. It IS an electronic flywheel, exactly what was asked for!

 

Andi