DCC Stay Alive Capacitators

Rhobat Bryn

DCC Stay Alive Capacitators

Postby Rhobat Bryn » Thu Mar 28, 2013 8:52 pm

Although the two locos I have so far are still a way off from being completed, I'm now considering having stay alive capacitators fitted come the day. I am also intending to adopt the Lenz DCC system.

I have seen reference to "DCC stay alive decoders".

I therefore would be grateful if anyone can shine any light on this clouded area of my modelling knowledge.

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Mike Garwood
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Re: DCC Stay Alive Capacitators

Postby Mike Garwood » Thu Mar 28, 2013 9:21 pm


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barhamd
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Re: DCC Stay Alive Capacitators

Postby barhamd » Fri Mar 29, 2013 12:07 am

I use the Lenz Power-1 options on the Lenz Gold chips on my 4-wheel industrial diesels (ok so it is 16m Narrow gauge not P4). I demonstrated this to the folks around here by running the locos on a yard of track with 6 inches of masking tape stuck over one rail. The loco just goes straight over it. Stopping the loco on the tape and reversing it off elicited the response 'that's not natural'.

Suffice to say i couldn't operate the my locos in the sand covered environment of Fen End Pit without them.

David Barham

Rhobat Bryn

Re: DCC Stay Alive Capacitators

Postby Rhobat Bryn » Fri Mar 29, 2013 11:11 am

Many thanks for the reference, Mike; an extremely informative discussion. It would appear that the way forward is the Lenz USP.

Also very useful to know that these things work in practice as well. I wonder if anyone has any P4 experience of stay alive capacitators.

Armchair Modeller

Re: DCC Stay Alive Capacitators

Postby Armchair Modeller » Fri Mar 29, 2013 11:43 am

There are other stay alive options, including DCC Concepts and TCS. There does seem to be some differentiation in the market between large capacitors, which can keep a loco running for a significant distance and those which simply iron out very tiny issues, like a spot of dirt on the track.

I bought a DCC-concepts decoer wth stay-alive already fitted. This was for a 4 wheel Sentinel shunter, where such a device is most likely to be useful. I have only tried it very briefly, as I want to leave the loco in DC mode whilst I am testing the track. Performance was impeccable with the stay-alive decoder, whereas with an ordinary decoder it was not quite as good.

This is part of the instructions for a DCC Concepts version.

The DCCconcepts “Stay-Alive”!

This simple device & its easy application to DCCconcepts decoders sets us apart from other brands.
Stay-Alive is a simple device. In basic terms, it stores power ready for the moment that the locomotive fails to make perfect contact with the track and
so loses “pickup”, starving the decoder and motor of the energy they need to keep operating properly.
Structurally, it is formed of several components all neatly arranged on a tiny PCB so that it takes up very little space and
so there is always somewhere you can find to install it in all but the tiniest of locomotives.

Stay-Alive Wiring is very easy:
There are two wires which exit the decoder at the opposite end to the main harness.
These are colour coded to match the Blue and Black wires of the Stay-Alive, so there is no doubt about how they should
be connected to each other (don’t forget to insulate the join between stay alive and decoder!).
Because Stay-Alive only deals with low current power it can be installed anywhere -not just close to the decoder.

What can you expect from the Stay-Alive?

Stay-Alive isn’t something that will keep loco’s moving over long dead sections of track and it is NOT a “Magic bullet” that will fix loco’s with bad pickups or filthy wheels of course - you still need to tune your locos so they run well before installation. It has been designed as an economical and effective way to compensate for short dead spots, to help locomotives with less than perfectly clean wheels or perfectly adjusted pickups and most importantly, it will help loco’s to stay silky smooth at very slow speeds.

What if you want MORE reserve power?

Actually if you have done a good job of adjusting pickups and cleaning
wheels you shouldn’t need it... But if you do want more energy storage than a single Stay alive will give, you can safely
parallel two onto a single decoder.

More than two is also possible, however you will probably find that because adding more than two in parallel will in-
crease charging loads and decrease current limiting resistor values, with more than two in parallel, your loco may no
longer read reliably on the programming track



Here is a link to a test done by Nigel Burkin https://www.model-railways-live.co.uk/R ... C_Decoders

and here, comments about TCS ones http://www.tcsdcc.com/public_html/Custo ... timonials/

nigelcliffe
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Re: DCC Stay Alive Capacitators

Postby nigelcliffe » Fri Mar 29, 2013 12:38 pm

Armchair Modeller wrote:There are other stay alive options, including DCC Concepts and TCS. There does seem to be some differentiation in the market between large capacitors, which can keep a loco running for a significant distance and those which simply iron out very tiny issues, like a spot of dirt on the track.


Very broadly, the difference in storage time is between Electrolytic Capacitors (typically give a fraction of a second of stay-alive) and "SuperCaps" (anything up to a minute of running).


The Electrolytics will transform a loco which appears to have tiny "stutterings". I have a High Level 0-4-0 battery loco which can be seen to just stutter without capacitors. With 1400uF of Electrolytics the stutter disappears; the effect is quite striking. Electrolytics are cheap (pence for a capacitor), and can be fitted to various decoders (some makers offer solder pads and advice on how to do this, or the internet will show up where to tack wires onto those without advice). Electrolytics can also remove small noises from sound decoders due to momentary drops in the pickup, and some sound decoder makers include a small electrolytic for that reason.
There are also 16v Tantalum capacitors which are slightly smaller per unit energy stored than Electrolytics. They are on my list for some more experiments.


SuperCaps move things into a different level of energy storage. They can run a loco for up to a minute, though 5-20 seconds is more typical. Before thinking "Fantastic, pickup problems fixed", have a think about how much damage a loco running off the track for 30 seconds can do to itself (you can only stop it if you can send a DCC "stop" instruction to the loco), particularly if a bit of valve gear has jammed as well ! I find SuperCaps to be a mixed bag because of the risks involved. I'd aim for 1-2 seconds maximum if using them.


As well as numerous Electrolytic fitted locos, I've used two sorts of SuperCap; the TCS KA2 (which I took apart to find out what's inside it, and its not a bad price compared to buying the parts yourself), and the Lenz Power-1 module (somewhat expensive in my view). The KA2 keeps my test loco (its a Scale-7 0-4-0 with a small Mashima motor) running for 20-30 seconds, well over a yard of track. The Power-1 module will run my 4mm scale Railbus (Airfix kit with Branchlines chassis) for just under a foot without power.
The Lenz decoder has some very smart electronics inside it which can detect whether the loco is on (or almost on) the track. It does this from the capacitance between decoder and rail. The net result is that the Power-1 module can power a loco over dirty track (or with paper masking the track), but if the loco is removed from the track (derails) the power is cut inside the decoder - very smart, but Lenz decoder only. The Power-1 is a Lenz-only device (unless you start taking it apart...).


If heading towards "DIY" circuits, then you need a diode and resistor (or two) in addition to the capacitor. The first resistor is fitted to limit the current into the capacitor when charging up (if not limited, then DCC system experiences infinite current demand and goes "overload" and shuts down). The diode is to by-pass the resistor during discharge of capacitor (give the chip/motor as much current as possible). The second resistor is to discharge the capacitor slowly, necessary for larger capacitance values (otherwise, you dismantle loco the next day, capacitor still charged, and you get a big electric shock and a bang when accidentally shorting something!).

With any form of capacitor, there is a trade-off between energy stored, rated voltage and physical size. Typically capacitors come rated at 16v, 25v and 35v. But, to store the same amount of energy, a 25v Capacitor is larger than a 16v one. Which to choose depends on the DCC system. If certain that track voltage is below 17v, then 16v capacitors are fine. If not certain, go for 25v (or even 35v if ultra cautious). If over-volted, a capacitor can explode rather violently. Some DCC systems have rather high track voltages, culprits I've met include Bachmann E-Z, Roco Multimaus. The usual "proper" makers of DCC systems such as Digitrax, NCE, Lenz, Gaugemaster, ESU, usually have track voltages below 16v.



My usual decoder of choice in 4mm scale is Zimo. There are solder pads on Zimo for adding capacitor circuits, and advice in the Zimo manuals on how to do it. Some Zimo decoders include the charging circuit for the capacitor. Zimo chips include some smart logic to avoid the loco stopping on a bit of dirty track - if the chip detects loss of pickup when coming to a stop, it will try to drive the motor a fraction further using the capacitor storage so it has stopped in clean track.
ESU have also recently provided instructions for adding capacitors, and sell a high-energy storage unit (like the Lenz Power-1) for their own decoders.


The TCS KA2 (and I guess the TCS KA1) include the charging circuit in their units. But no discharge. I added a resistor over the KA2 wires to ensure discharge within 25 minutes of removal from the track. TCS KA units are fitted with 16v rated capacitors, so only use on layouts with track voltage below 17v.





- Nigel

Rhobat Bryn

Re: DCC Stay Alive Capacitators

Postby Rhobat Bryn » Sat Mar 30, 2013 5:38 pm

Thank you Armchair and Nigel for those insights. I think I will be going for the Lenz Power-1 module when the time comes complete with the Lenz gold mini decoder; but it's very helpful to understand the technology involved as well as the wider picture.

As an afterthought, does this stay alive technology help with locos that stall when required to start off from standing, say at a station?


Rhobat

martin goodall
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Re: DCC Stay Alive Capacitators

Postby martin goodall » Sat Mar 30, 2013 7:04 pm

This question will reveal my total ignorance of matters electrical and electronic, but is this technology available (or can it be adapted) for non-DCC use, i.e. for locos running on 0 - 12 volts Direct Current, using orthodox (non-DCC) control systems?

If so, can somebody point me to the relevant literature / product details, etc?

nigelcliffe
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Re: DCC Stay Alive Capacitators

Postby nigelcliffe » Sat Mar 30, 2013 7:08 pm

I regard the Gold Mini as very overpriced for the quality it delivers. If fitting the Power-1, then many locos will have space for the standard sized Gold (rather than the Mini). Perhaps one Gold plus Power-1 as its a simple tested one-maker solution. But look elsewhere/wider once you have one under your belt.


Stay Alive's won't fix a loco which develops resistance (due to thin film of dirt) when standing. But, in other respects, yes it does help with starting as well as running.


- Nigel

nigelcliffe
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Re: DCC Stay Alive Capacitators

Postby nigelcliffe » Sat Mar 30, 2013 7:15 pm

martin goodall wrote:This question will reveal my total ignorance of matters electrical and electronic, but is this technology available (or can it be adapted) for non-DCC use, i.e. for locos running on 0 - 12 volts Direct Current, using orthodox (non-DCC) control systems?

If so, can somebody point me to the relevant literature / product details, etc?


In theory, it is possible - I've seen someone lash a test example up, but it pretty much filled a Lima Bogie diesel loco, and created some interesting control side-effects. But, by the time you've added a load of electronics, control circuits, etc.. then you might as well fit a smaller (due to mass miniaturisation in manufacture) DCC decoder and use a DCC controller.

The alternative, which takes things well away from DCC and DC control, is to use battery radio control. This removes the need for any track pickup. There are some very compact solutions around (using lithium polymer batteries), some very cheap simple and compact (eg. inside a Minitrix N gauge small tank engine), others costing a bit more but offering the potential for very sophisticated control. And there is the rather less compact 9V PP3 solution featured in a recent MRJ. But all of these do involve putting a control circuit, plus battery, inside the loco.


- Nigel

Rhobat Bryn

Re: DCC Stay Alive Capacitators

Postby Rhobat Bryn » Sat Mar 30, 2013 8:08 pm

nigelcliffe wrote:I regard the Gold Mini as very overpriced for the quality it delivers. If fitting the Power-1, then many locos will have space for the standard sized Gold (rather than the Mini). Perhaps one Gold plus Power-1 as its a simple tested one-maker solution. But look elsewhere/wider once you have one under your belt.


Stay Alive's won't fix a loco which develops resistance (due to thin film of dirt) when standing. But, in other respects, yes it does help with starting as well as running.


- Nigel


I'm interested in your comment about the quality of the Gold Mini+. My reason for choosing the Mini is that the majority of my locos will be tank engines and I assume that space is at a premium in these models expecially if room also has to be found for a USP module. But would I be right in assuming that the Gold Mini+ is somewhat inferior in quality of the standard-sized Gold decoder in your experience?

Rhobat

nigelcliffe
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Re: DCC Stay Alive Capacitators

Postby nigelcliffe » Sat Mar 30, 2013 8:53 pm

Rhobat Bryn wrote:I'm interested in your comment about the quality of the Gold Mini+. My reason for choosing the Mini is that the majority of my locos will be tank engines and I assume that space is at a premium in these models expecially if room also has to be found for a USP module. But would I be right in assuming that the Gold Mini+ is somewhat inferior in quality of the standard-sized Gold decoder in your experience?

Rhobat


I find Lenz decoders to offer inferior motor control (and notably inferior ability to fine tune the control) when compared to some other makers, notably Zimo(*). So, with the Mini-Gold costing around £42 the smaller Zimos such as the MX621/MX622 at £30-33, the Mini-Gold is poor value in my opinion.

The Power-1 module is quite big. If you have room for that, I'd expect there is space for a "normal" sized decoder, though obviously there will be cases where Power-1 plus Mini is all that will fit.

The standard Lenz Gold is (or at least "was the last time I looked") a lot cheaper than the Mini.


In terms of finding space, then "rolling your own" with descrete capacitors placed around the model will probably be easier in small locos. You can link capacitors in parallel to add the storage together. But, if staying with the simpler electrolytics, the power storage is "anti stutter", not "perform tricks over paper covering track". Anti-stutter is enough if your locos and track are basically sound to begin with.


(* if really stuck for space, such as 2mm scale, I would use CT Elektronik. Motor control superb, and smaller than anything else on sale by a considerable margin. But, they are a bit fragile, documentation terrible, adding storage capacitors involves micro-soldering onto tiny chips (very scary!) so Zimo is a safer bet if there is space. )


- Nigel

Rhobat Bryn

Re: DCC Stay Alive Capacitators

Postby Rhobat Bryn » Sun Mar 31, 2013 4:37 pm

nigelcliffe wrote:
I find Lenz decoders to offer inferior motor control (and notably inferior ability to fine tune the control) when compared to some other makers, notably Zimo(*). So, with the Mini-Gold costing around £42 the smaller Zimos such as the MX621/MX622 at £30-33, the Mini-Gold is poor value in my opinion.

- Nigel


Accepting your point about the Zimo decoders, have you noticed a difference in performance between the standard Lenz Gold decoder and the Gold Mini+?

Rhobat

nigelcliffe
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Re: DCC Stay Alive Capacitators

Postby nigelcliffe » Sun Mar 31, 2013 5:19 pm

Rhobat Bryn wrote:
Accepting your point about the Zimo decoders, have you noticed a difference in performance between the standard Lenz Gold decoder and the Gold Mini+?

Rhobat


I have not done enough testing to reach a conclusion on that question.
In general, manufactures use the same firmware inside all their decoders. The smaller models are just the smaller footprint version of the same microprocessor (a standard device which lots of makers would use) and lower power and smaller components for the motor and function final drive. It is those lower powered final output components which mean the smaller decoders tend to have lower power ratings.

- Nigel

nigelcliffe
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Re: DCC Stay Alive Capacitators

Postby nigelcliffe » Sun Jul 21, 2013 3:56 pm

nigelcliffe wrote:.....


In terms of finding space, then "rolling your own" with descrete capacitors placed around the model will probably be easier in small locos. You can link capacitors in parallel to add the storage together. But, if staying with the simpler electrolytics, the power storage is "anti stutter", not "perform tricks over paper covering track". Anti-stutter is enough if your locos and track are basically sound to begin with.


(* if really stuck for space, such as 2mm scale, I would use CT Elektronik. Motor control superb, and smaller than anything else on sale by a considerable margin. But, they are a bit fragile, documentation terrible, adding storage capacitors involves micro-soldering onto tiny chips (very scary!) so Zimo is a safer bet if there is space. )




Further experiments with stay alive are on my blog. If its possible to get effective stay-alive into a 2mm scale 0-4-0 shunter, then there won't be much in 4mm scale which is "impossible", just the determination to make it work.

http://nigelcliffe.blogspot.com

- Nigel

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Andy W
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Re: DCC Stay Alive Capacitators

Postby Andy W » Sun Jul 21, 2013 8:19 pm

These "Stay alive capacitors" could I have a couple fitted to me?
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Armchair Modeller

Re: DCC Stay Alive Capacitators

Postby Armchair Modeller » Sun Jul 21, 2013 8:43 pm

Why two? Are you leading a double life? ;)

Nigel - that 2mm implementation really does impressive. I recently fitted a stay alive with decoder to my 4mm Sentinel and am very pleased with its performance improvement - not that it was ever really bad. I am now looking to fit these to all my future locos. I don't feel up to making my own, but in 4mm scale, I doubt if I would need custom versions.


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