Model Railway Forum banner
1 - 15 of 15 Posts

·
Premium Member
Joined
·
2,882 Posts
Discussion Starter · #1 ·
I am thinking about fitting stay-alive capacitors in some of my locos. The main reason for doing this is connected with their sound decoders. All my locos are fitted with sound. Some (but not most of them), if they experience even a momentary cut in power from the track, shut off the sound and it does not automatically come back on. The loco continues to move because its momentum has taken it past the cause of the problem but without sound.

What sort of capacitors do I need? (Many years ago I read about ordinary and electrolytic capacitors.) Also what capacitance would I need to cover only a second's break in power? Where is a good place to get them? I have looked ay DCC Concepts website but it appears that they don't sell them on their own, only attached to decoders (if I've read the site correctly).

Thank you.
 

·
Administrator
Joined
·
9,941 Posts

·
Premium Member
Joined
·
2,882 Posts
Discussion Starter · #3 ·
Thank you for the information. Actually, a stay alive that makes the loco run that length is not what I want. I store trains in a tunnel by bringing them to a stop in a dead section. I don't want a capacitor that will move one more than a few centimetres or the loco will run into the next live section. Perhaps stay-alive is not such a good idea. I'm sorry if I have wasted your time, David

Robert
 

·
Registered
Joined
·
2,536 Posts
Personally, I would be addressing what is causing the momentary power losses - dead rails, failed droppers, failed turnouts, dead frogs (should be replaced with live frogs), cleaning, track level quality, wheel trueness, pickups etc.

Most of my locos are also 'noisy' but none have stay alive.

To me, 'stay alive' is a bit of a band-aid which allows people to carry on bad practices without solving them by masking them.

Stay alive has a place, but only as a last resort. For me, I only have one such loco and that is the late model Hornby 61xx. The axles are rigid, meaning that any change in track 'twist' (my curves have proper cant and transitions) can cause loss of power. Having said that, it is currently running with a Zimo MX600R which seems to be able to cope with minor dropouts.

Most of the time, dropouts can be fixed with extra pickups.
 

·
Chief cook & bottle washer
Joined
·
2,958 Posts
Hi Robert,
You can use a small stay alive to give a very short amount of run time while keeping the sound going. Tell us what make of decoders you're using and we should be able to help you.
 

·
Premium Member
Joined
·
223 Posts
Hi Robert

I have fitted many of my small tank locos with stay alive for the same momentary blip. I have got them from youchoos, they are happy to give advice over the phone and have seceral sizes available.

Derek
 

·
In depth idiot
Joined
·
7,961 Posts
... Actually, a stay alive that makes the loco run that length is not what I want. I store trains in a tunnel by bringing them to a stop in a dead section. I don't want a capacitor that will move one more than a few centimetres or the loco will run into the next live section...
That conflict from your choice of operational method rules out any significant stay alive.

...Having said that, it is currently running with a Zimo MX600R which seems to be able to cope with minor dropouts.
There you are touching on an aspect of decoder design that I have never looked into. When starting out in DCC, I tested ever decoder readily available at retail outlets in the UK. Some were vastly superior to others. This testing was on my old (long gone) layout with a number of yard points that were Peco dead crossing type, and the sparking when a wheel bridged the rails after the crossing was quickly apparent. The superior decoders didn't miss a beat when a loco pick up wheel caused such a short, despite the disruption to current collection, and I concluded at the time that these decoders must have a small amount of power storage on board. I don't recall this ever being described in decoder specs.
 

·
Registered
Joined
·
828 Posts
I store trains in a tunnel by bringing them to a stop in a dead section. I don't want a capacitor that will move one more than a few centimetres or the loco will run into the next live section.
If you bring a loco to a stop then a stay alive will not make it move further.

You should not be using dead sections with DCC, it's totally unnecessary, complicates the wiring and defeats the whole point og the controllability that DCC gives you.
 

·
Premium Member
Joined
·
2,882 Posts
Discussion Starter · #10 ·
Let me explain why I use dead sections. Each storage track is long enough to hold two complete trains with about 10cm between them. The front train loco is sitting on a dead section which I can energise when I want to bring the train out of the tunnel onto the scenic section. When this happens an infra-red sensor 'sees' that the train has gone and automatically energises the dead section that the loco of the rear train is sitting on. It therefore moves forward into the space previously occupied and now becomes the front train and stops in the dead section which is no longer energised. This leaves the rear space available for the train on the scenic section to run into when it enters the tunnel. Of course because it's a tunnel I can't see any of this happen. I need the rear train loco to start when given power without me doing anything. I do slow fast-running trains when they enter the tunnel but leave them going to stop in the dead section which I can't see.

Perhaps my layout design is too complicated. I certainly won't use this idea if I ever start again, but I'm too far on to change it now. All I can say is that it seemed like a good idea at the time. I suppose I could eliminate the problem by only having one train on each storage track but that would severely reduce the variety of trains available.
 

·
Registered
Joined
·
1,668 Posts
I am thinking about fitting stay-alive capacitors in some of my locos. ..........

What sort of capacitors do I need? (Many years ago I read about ordinary and electrolytic capacitors.) Also what capacitance would I need to cover only a second's break in power? Where is a good place to get them? I have looked ay DCC Concepts website .....
These days, I have moved to fitting the Lais units which Digitrains retail for £15 each. They have a lot of energy for the price. For tighter spaces, the components from YouChoos will fit in smaller spaces, and extreme spaces I'll use DIY stuff with surface-mount components for charge/discharge/voltage limiter, and tantalum capacitors (best option for small space, but nothing like the energy density of super-caps).

On the horizon is a new stay-alive module with voltage doublers and small super-caps from Zimo. Not yet tried it, or checked dimensions for space, but theory looks promising.


In all cases, need to understand track voltages for choice of components. All decoders can, in principle, have a stay-alive fitted, its a matter of finding the decoder positive and negative connections. Some decoders are easier than others, some makers document things for you. Some of the newer decoder sockets (Plux, Next) are much easier as the contacts exist at the decoder socket into the loco.


Personally, I would be addressing what is causing the momentary power losses - dead rails, failed droppers, failed turnouts, dead frogs (should be replaced with live frogs), cleaning, track level quality, wheel trueness, pickups etc.

Most of my locos are also 'noisy' but none have stay alive.

To me, 'stay alive' is a bit of a band-aid which allows people to carry on bad practices without solving them by masking them.
I agree with fixing dead rails, droppers, pickups, etc. And, then having done that, with many locos I'm still fitting stay-alives. Because it makes a noticable difference in reliability and smoothness of running. The effect is more marked on tank locos with four or six wheels, and is tailing off with bogie diesels, due to their increased wheel count.

I've had the "its not needed" comment from many people. Then I've persuaded them to let me fit into one loco of theirs. I now have regular repeat orders for stay-alives from those people. Most recent fitting repeat request arrived yesterday evening.


- Nigel
 

·
Registered
Joined
·
2,536 Posts
... And, then having done that, with many locos I'm still fitting stay-alives. Because it makes a noticable difference in reliability and smoothness of running. The effect is more marked on tank locos with four or six wheels, and is tailing off with bogie diesels, due to their increased wheel count.

I've had the "its not needed" comment from many people. Then I've persuaded them to let me fit into one loco of theirs.
Thanks Nigel.

Correct me if I am wrong, but I seem to recall that you are a 2mm scale modeller ?
In that context, I would certainly agree with you that stay alive offers benefits. My dabbling with 2mm scale has been with 009 and I often found that locos were loosing continuity through motor vibration or just general lack of weight or wobbling. My main foray into 009 was back in my 'DC days' and in those days, I used to use Relcos and they certainly made a positive difference in the absence of any other solution at the time.

In 4mm scale, I don't have any 0-4-0's, but I can see that they would benefit from stay-alive. I have a number of 6-coupled locos and apart from the late model Hornby 61xx, I have never had any problems which have required stay-alive.

When it comes to laying track, I am extremely fussy about the quality of workmanship I apply. I get it drawn out on my father's CAD software which he used in his profession as a prototype track design engineer and then I mark it all out on the boards, including alignments and correctly mathematically calculated cant and transitions. As a result, my track is very level with no rises across board joints and no slacks. I use Peco code 75 and I make sure that all of my B2B's are pushed out to 14.5mm as they should (none of this gauge narrowing nonsense promoted by some people!) which means I don't get wheels dropping into common crossings. I guess this level of effort is extremely unusual, but it has meant that stay-alive really doesn't give me much benefit, plus of course, the vast majority of my locos are 4-6-0s from the proper railway or they are diesels. I guess I'm just lucky. And extremely fussy! Sadly, most layouts I have observed which use RTR track don't have it laid to comparable standards and I have often had to train others in track laying.

Happy modelling!
 

·
Premium Member
Joined
·
2,882 Posts
Discussion Starter · #14 ·
Most are ESU Loksound but one is a Zimo sound decoder.

Thank you all for the help but I now realise that stay-alive capacitors will not be suitable in my situation. It was a case of not thinking things through clearly enough.
 

·
Registered
Joined
·
1,668 Posts
Thanks Nigel.

Correct me if I am wrong, but I seem to recall that you are a 2mm scale modeller ?
In that context, I would certainly agree with you that stay alive offers benefits...........

In 4mm scale, I don't have any 0-4-0's, but I can see that they would benefit from stay-alive. I have a number of 6-coupled locos and apart from the late model Hornby 61xx, I have never had any problems which have required stay-alive.

When it comes to laying track, I am extremely fussy about the quality of workmanship I apply. ........
My background is 2mm finescale, but I'm doing more 4mm modelling these days in P4 and EM. Most of the decoder installations I do are for 4mm scale.

Yes, track needs to be correct. I think the stuff I work with is likely to be similar quality of engineering on the track and infrastructure side.


About ten days ago I delivered another 0-4-0 installation, into a Hattons Barclay tank. Loco is transformed from "annoying, because of the stopping and stuttering", to "totally reliable". This followed on from a couple of Bachmann J72's - simplest installation in any RTR loco I've yet seen, with solder pads on the loco PCB for connecting the stay-alive.


- Nigel
 
1 - 15 of 15 Posts
Top