Keep-alive for DC?

[AndyID]

3 hours ago, Barclay said:

In MRJ 109 was an article called 'The Electronic Flywheel' -  He worked in 7mm, used 2 x 470 microfarad capacitors, (36 volt, non-polarised) and with RG7 motors achieved a run-on of 1/3 of a loco length. This would be plenty to prevent stalling on a grain of dust etc. and not enough to require any kind of control circuitry to prevent running away. I assume the new capacitors are much less bulky. 

 

Yes, much smaller. 12 x 8 mm. Unfortunately I have to use eight of them for 12 volts.

[AndyID]

I'm charging the banks to a maximum of 11.15 volts and the voltages on the individual caps range from a low of 2.73 volts to a high of 2.85 volts.

 

The other reason I'm messing about with this is because I have a half-baked idea about radio control with "not quite dead rail" using supercaps instead of batteries, mainly for shunting. For that I'd probably use low voltage motors then I might only need one supercap - probably something like 5 F.

[wasdavetheroad]

11 hours ago, AndyID said:

I'm charging the banks to a maximum of 11.15 volts and the voltages on the individual caps range from a low of 2.73 volts to a high of 2.85 volts.

 

The other reason I'm messing about with this is because I have a half-baked idea about radio control with "not quite dead rail" using supercaps instead of batteries, mainly for shunting. For that I'd probably use low voltage motors then I might only need one supercap - probably something like 5 F.

You might consider using a battery rather than a supercap. If you are using radio control you have the possibility of using a voltage regulator to ensure a fixed voltage to the receiver both from the track supply and the battery. The receiver than varies the pulse width modulated voltage to the motor using commands from the radio controller. Actually for shunting you might as well just use the battery, less complicated. 

 

BlueRail Trains first board, the one I bought for testing, automatically switched between track and battery and it was seamless if you had the same voltage with both.

 

Having an automatic DC/DCC/battery switching system with auto battery charging on powered track is the holy grail of power supplies. All the elements work and it just needs someone to integrate them into a small package. 

[AndyID]

14 hours ago, wasdavetheroad said:

You might consider using a battery rather than a supercap. If you are using radio control you have the possibility of using a voltage regulator to ensure a fixed voltage to the receiver both from the track supply and the battery. The receiver than varies the pulse width modulated voltage to the motor using commands from the radio controller. Actually for shunting you might as well just use the battery, less complicated. 

 

BlueRail Trains first board, the one I bought for testing, automatically switched between track and battery and it was seamless if you had the same voltage with both.

 

Having an automatic DC/DCC/battery switching system with auto battery charging on powered track is the holy grail of power supplies. All the elements work and it just needs someone to integrate them into a small package. 

 

Which battery would you recommend for a OO L&Y Pug?

[wasdavetheroad]

11 hours ago, AndyID said:

 

Which battery would you recommend for a OO L&Y Pug?

It depends on what you want the loco to do and how long you want it to do it!. Then you have to find the space for the battery and associated electronics.

 

The smallest loco I have converted is a Hornby Railroad Smokey Joe 0-4-0, just to see if I could do it. I managed to fit the receiver and a single 100mAh battery and removed the track pickups which always improves performance. Smokey Joe does not have the most advanced mechanism.

 

Testing - maximum speed running light engine with a fully charged battery was somewhat over 30mph. Pulling wagons somewhat slower. I set the receiver maximum speed to 20mph and ran an endurance test. Pulling those 4 wagons the receiver switched off the power to stop the battery over discharging at about 3V. This was after 45 minutes during which the loco had completed 27 circuits of my 5x2 metre layout. from this I calculated that the loco power requirement with 4 wagons was 135mA, in other words to run for 1 hour would need a 135mAh capacity battery. If the loco is not doing anything, just stabled for example, the onboard receiver uses about 15mA per hour. the battery voltage dropped from 4.2V to 3V over the test and the speed dropped from 20mph to 18.5mph.

 

Use per operating session - My Smokey Joes job is to move gypsum wagons to/from a off layout gypsum mine and there is a fictional steep gradient up from the mine. Full wagons are restricted to 3 which must be pushed. Typically the loco can drag 9 empties to the mine and during the rest of the session propels 3 batches of 3 back to the exchange siding. This is about equivalent to about 5 layout circuits taking about 12 minutes and using about 27mAh of battery capacity, say 30mAh. 

 

This leaves the 100mAh battery with about 70mAh spare capacity. This means the loco could sit idle for over 4.5 hours plus the 12 minutes running before the receiver cut the power to save the battery. As my operating sessions are 2-3 hours there are no problems. You could even use a smaller 70mAh battery if the loco was not switched on until needed.

 

I remove my batteries for recharging and they are E-flite types with 'UM' connectors. changing the battery for a fresh one should take less than 30 seconds!

[AndyID]

I finally got around to attaching the cap to a test "mule" (a much modified Tri-ang 3F with a small Sagami open-frame motor and a lot of reduction gearing).

 

The results are quite impressive. Running on regulated DC I can set it going at a crawl and it chugs along without a hiccup on rather dirty track. (Without the cap it tends to stall at low speed.) Control doesn't seem to be a problem either. I can slow it down to a crawl without fear of stalling and gently nudge the buffers.

 

When I've installed the caps properly I'll try to post a video.

[AndyID]

This is where I ended up.

 

At first I thought I would need eight 3 volt caps for 12 volts, but it only takes four. The combination of four 1F caps in series produces an effective capacitance of 250,000 micro-farads which will allow any locomotive to cruise through a dead frog without any hesitation. Using pure DC, crawl speed over a long distance is pretty impressive too.

 

These caps are 8mm in diameter and 12 mm long.

 

This method of connecting electrolytic capacitors back-to-back to create a non-polarized capacitor has been around for a very long time but it's usually used with AC where some amount of charge oscillates between the caps. This is a bit different and there could be some degradation of the caps over time. I have not noticed any but I have not conducted a lot of tests.

 

Oh, and Happy New Year!

 

 

 

 

 

Edited January 1, 2021 by AndyID
missing verb

[AndyID]

and here's the video

 

https://youtu.be/L1q0UomS6qQ

[hobbyhorse]

On 19/11/2020 at 14:18, Barclay said:

In MRJ 109 was an article called 'The Electronic Flywheel' -  He worked in 7mm, used 2 x 470 microfarad capacitors, (36 volt, non-polarised) and with RG7 motors achieved a run-on of 1/3 of a loco length. This would be plenty to prevent stalling on a grain of dust etc. and not enough to require any kind of control circuitry to prevent running away. I assume the new capacitors are much less bulky. 

We developed that system for it's simplicity, my friend who was an electrical engineer did the article and we fitted the rest of the locos on our exhibition layout Tewksbury with them. We never had any running problems after that.

Simon

[AndyID]

Another video featuring a much maligned Hornby tender-drive Black Five. (The motor is in the tender driving the loco's wheels.) Four 1 Farad caps in the tender. Smooth DC only. The DVM shows the track voltage. The track has not been cleaned in quite a while.

 

When both switches are OFF the loco is running on capacitor power. (I had to use two switches because I could not find one with a center OFF. I'm sure I have one somewhere )

 

The video is here:

https://youtu.be/I13EPnmBuz8

[d00m]

That is impressive. Useful for another application ?  I think you may have simplified an automatic signalling/gentle stop  problem that I have been wrestling with for a few years.

Edited January 3, 2021 by d00m

[AndyID]

20 hours ago, d00m said:

That is impressive. Useful for another application ?  I think you may have simplified an automatic signalling/gentle stop  problem that I have been wrestling with for a few years.

 

It definitely produces smooth stops and starts and it does seem to work very well for low speeds and shunting. You could use it for automation but you might have to tune each loco to get consistent behavior. You can reduce the total capacitance by adding additional pairs of capacitors and/or add resistors across the capacitor bank to increase the discharge rate when the power is cut.

[Phil Himsworth]

That is really interesting, thank you. I ordered a load of capacitors yesterday for another application but because of the batch size I have far more than I need so I'm tempted to try your idea; that video of the Black 5 is very impressive.

[AndyID]

As you can see this Bachmann split-chassis Jubilee is having some serious pickup problems. (For some unknown reason it seems to be worse in reverse.) Then I clipped on the supercaps and repeated the run.

 

Sorry about the wobbly and blurry bits

 

 

 

 

 

[DCB]

That is one very sick Jubilee.   Like most ageing split chassis locos it really needs pickups between chassis and driving wheels like I fitted to split chassis Standard 4MT Lord Nelson, B1 etc before the wheels fall off.   Stay alive should be for dirty track not keeping worn out locos going.   

[AndyID]

2 hours ago, DavidCBroad said:

That is one very sick Jubilee.   Like most ageing split chassis locos it really needs pickups between chassis and driving wheels like I fitted to split chassis Standard 4MT Lord Nelson, B1 etc before the wheels fall off.   Stay alive should be for dirty track not keeping worn out locos going.   

 

Indeed so, but (apart from you and me) how many of us are actually capable of installing decent pickups? (I'd probably add them to the tender too, but that's just me.)

 

On the other hand, stuffing a few small caps into a loco or its tender is something almost anyone with a soldering iron can do and solve both the dirty track and lousy pickup problems all in one go. What could possibly be wrong with that?

 

You could always try adding the caps to a couple of locos and see how it goes. It's not a very expensive modification and you might even like the results. (The flywheel action is really cool, but only if you happen to like that sort of thing.)

 

 

Edited January 7, 2021 by AndyID
As usual.

[kevinlms]

2 hours ago, DavidCBroad said:

That is one very sick Jubilee.   Like most ageing split chassis locos it really needs pickups between chassis and driving wheels like I fitted to split chassis Standard 4MT Lord Nelson, B1 etc before the wheels fall off.   Stay alive should be for dirty track not keeping worn out locos going.   

If it does the job, why not?

 

The only problem I see with the idea, is how many locos would have trouble hiding the capacitors? Agreed that with Andy's loco, they can go in the tender, but small tank engines?

[AndyID]

24 minutes ago, kevinlms said:

If it does the job, why not?

 

The only problem I see with the idea, is how many locos would have trouble hiding the capacitors? Agreed that with Andy's loco, they can go in the tender, but small tank engines?

 

Hi Kevin,

 

The caps really are not very big and they should fit into most 00 tank engines. I'll give that a shot in a Kitmaster/Airfix pug and see how it goes.

 

I'm really not very interested in proving anything. I'd just like everyone to appreciate a body of science rather than creating some alternative science.

 

Cheers,

Andy

[Broadway Clive]

Brilliant work Andy. You seem to have blown open the lid on a subject that others have been trying to keep shut for years now! Could you post an updated diagram with the list of components so we can source them locally and try it out please? I'm wondering if it will tolerate HF track cleaners and feedback controllers. Any ideas about those?

[AndyID]

13 hours ago, Broadway Clive said:

Brilliant work Andy. You seem to have blown open the lid on a subject that others have been trying to keep shut for years now! Could you post an updated diagram with the list of components so we can source them locally and try it out please? I'm wondering if it will tolerate HF track cleaners and feedback controllers. Any ideas about those?

 

Hi Clive,

 

So far so good but it would be good to do a bit more testing to find out if there are any snags.

 

The caps I used are available in the UK. Here is one source.

https://www.mouser.co.uk/ProductDetail/AVX/SCCR12E105PRB?qs=qSfuJ%2Bfl%2Fd7z2XKk8jG7Cg==

 

See my post December 31 for how to connect them.

 

It's important not to exceed the working voltage of the caps. Four of these 3 volt caps in series are only good for 12 volts. I'm using a variable smooth DC regulator as a controller.

 

I would not recommend using HF track cleaners with them as that might damage the capacitors. Certain types of feedback controllers will work with them but I suspect most will not. I have not tried any (actually I don't have any ) although I do have some ideas I might try.

 

Cheers,

Andy

 

 

 

Edited January 10, 2021 by AndyID
More info.

[AndyID]

I posted this video as a link previously. Here it is embedded.

 

 

[AndyID]

Another video. This time with the caps on the loco disconnected. The meter is showing the DC track voltage.

 

 

Same thing except the caps on the loco are now connected.

 

 

Nothing up my sleeves, 'onest guv. The 3F chassis collects current on all wheels. The wheels and track are not impeccable, probably pretty typical. No pulse power, no nuthin. Just smooth DC from a LM217 regulator.

 

 

Edited January 22, 2021 by AndyID
Wrong links

[AndyID]

I've been doing a bit more testing and a bit of thinking (in between a bit of skiing  - plenty of snow here at the moment and as I'm 65+ I've had my first vaccination).

 

The testing continues. It's not exactly an industrial strength test program but so far I've not observed any degradation in the "electronic flywheel". Actually, I'm pretty surprised at how very consistent it is. Shunting is a breeze, particularly with Kadee delayed action couplers.

 

The thinking part is more to do with why it actually works. Traditional electrolytic capacitors are very polarity sensitive. They do not like to be reverse biased at all.

 

The odd thing about these caps is they are supposed to be polarized but they seem to be quite happy to store charge of either polarity. When two of them are connected back-to-back they divide the applied voltage and they both discharge stored energy into the load at the same rate. Further testing reveals that they really don't care which terminal is positive or negative as long as I allow time for the cap to discharge before I reverse the polarity.

 

I did a bit of digging and it seems that with these particular caps the structure is likely symmetrical and the polarity designation somewhat arbitrary. If that's true it should not matter how I connect them in series. I'm going to try that next and see what happens.

[Phil Himsworth]

I got around to having a quick play; after a false start involving some capacitors with a very high ESR, which maintained the voltage but put out about 300mA maximum so were hardly going to be much use here, I made a 30 year old Smokey Joe run the best he has ever done!

 

What puzzled me the most is how it makes starting more reliable; I assume the difference is that when the loco is stopped it's because the capacitor has run out, not because the loco has reached a spot with poorer power pickup while moving very slowly and gets stuck.

 

The biggest problem with Smokey Joe is that, unloaded at least, 4 1F capacitors is far too much - if you accidentally give him a burst of high power he will travel well over a metre. Or rather he would, but he will probably crash into something before getting that far. It is quite a challenge to drive! I might try some smaller caps to see if that will achieve the positives without being quite so overkill.

 

This "caps plonked in a wagon" approach may be replaced with something resembling a shunter's wagon if I get round to it.

 

 

 

Edited September 2, 2022 by Phil Himsworth
Fixed image

[AndyID]

1 hour ago, Phil Himsworth said:

I got around to having a quick play; after a false start involving some capacitors with a very high ESR, which maintained the voltage but put out about 300mA maximum so were hardly going to be much use here, I made a 30 year old Smokey Joe run the best he has ever done!

 

What puzzled me the most is how it makes starting more reliable; I assume the difference is that when the loco is stopped it's because the capacitor has run out, not because the loco has reached a spot with poorer power pickup while moving very slowly and gets stuck.

 

The biggest problem with Smokey Joe is that, unloaded at least, 4 1F capacitors is far too much - if you accidentally give him a burst of high power he will travel well over a metre. Or rather he would, but he will probably crash into something before getting that far. It is quite a challenge to drive! I might try some smaller caps to see if that will achieve the positives without being quite so overkill.

 

This "caps plonked in a wagon" approach may be replaced with something resembling a shunter's wagon if I get round to it.

 

 

 

 

Way to go Phil!

 

I don't think you'll be able to find smaller caps but you can reduce the capacitance by putting more of them in series although that will only help a bit.

 

It's quite possible to build a controller that has a push-pull output so that it discharges the capacitors when you want to slow a train down. You can get some of that effect by simply hanging a power resistor across the output of your controller, but an active pull-down transistor will be better. BTW, what type of controller are you using?

 

Like me you noticed the dramatic improvement at slow speeds. I think that's because the motor voltage is essentially constant. It's very difficult to achieve that with typical rail/wheel and wheel/pickup contact. There's always a certain amount of variability in the resistance while a loco is moving and it doesn't take much to cause stalling. The caps eliminate that almost entirely.

 

The other trick I've been using is to set the controller at a crawl speed and feed it through an on-off-on reversing switch. It's great for shunting and the amount of inertia is highly realistic.

 

Now to do some more experiments. I'm thinking five caps might be better as it will provide a bit more voltage margin at twelve volts.

 

Cheers,

Andy