Stay Alive Capacitors

[DEREK123]

Hi HB

 

Sorry to bother you but I now have the capacitors as recommended and I am ready to solder

                                                                 BUT!! 

The blue wire goes to which pin of the capacitor  ?  (  + or - , long or short ? ) , and the black wire to ?

I can't tell from your photo ( the one you did earlier !! ) and I can't find anything on the net to help me .

Thanks

Derek

[Howbi]

@Derek........the Blue wire joins to the long lead.......the Black wire joins to the short lead which is near the pale blue band on the cap marked with dashes......heat shrink recommended to cover bare bits...... 😀......HB

[Fishmanoz]

Chris told you in his second post on page 1.

[Howbi]

@aas..........re your question re: fitting a stay alive to a TTS decoder.......

 

@Chrissaf........Chris, can you confirm this is correct?.........HB

/media/tinymce_upload/1c591329a9a1f9e8b66ff43f1ab6a882.png

[Chrissaf]

HB, I recognise that as being my drawing, so I'm unlikely to say it is wrong 😉

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But seriously though, the copper track going to the blue (positive) wire can clearly be seen connecting to the pad marked with the red circle. And the rectifier diode layout is virtually identical to the R8249 decoder connection points reproduced below from a previous 'Stay Alive' posted thread:

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/media/tinymce_upload/515e060fd4c8cc2ba1d77ab11a4266b0.jpg

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Just for the elimination of doubt. The red and blue stay alive capacitor connections in the drawings (both of them) represent positive and negative polarity and not the colour of the stay alive wires. From other posts in this thread the the stay alive blue wire is the positive and the stay alive black wire is the negative. I used blue rather than black in the drawing because blue stood out better than black.

[DEREK123]

@ HB , Thanks ..... I fitted the heat shrink too.

@ Fishmanoz , Your memory is a lot better than mine !! ... doh !!

@ Chris , Thanks  😳

Derek

All done and working fine ... thanks again guys.

[Fishmanoz]

No worries Derek, glad you got it working.  And remember, blue is always common positive on decoders, including for stay alive.

[choralc]

Would one 4700uF be of value even at 26mm x 13mm if their is the space?

[Chrissaf]

Choralc,

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If you review the post I made at 20:35 on the 20th (Page 2 of this thread). I wrote and I quote below:

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"In terms of which one. Search for an Electrolytic capacitor. Basically the largest uF (micro-Farad) value you can get that is physically small enough to fit in the space available."

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So yes, if you can physically fit a 4,700uf capacitor instead of a 2,200uF then you will double the stay alive time.

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If your comment is regarding one larger value versus two smaller values. Then take into account that the original question raised in the post related to a commercial DCC concepts stay alive product as opposed to the final DIY solution that was implemented.

[The son of Triangman]

When you think of it, "stay alive" is only an easily found electrolytic capcitor, a resistor and a diode, it's scandalous what people pay for the so called special "stay alive" decoders that are commercially available. 

[The son of Triangman]

A good quality electrolytic 2200uf capacitor will cost around a £1 from electronic companies such as CPC and Rapid. Just shows how much of a rip off the so called stay alive decoders are. A bog standard 1 Amp diode will cost around 20p, two are usually used. A suitable resistor will cost around 1 -2 pence.

Diodes

http://cpc.farnell.com/unbranded/p600d/diode-6a-200v/dp/SC07359

 

1000uf

http://cpc.farnell.com/panasonic-electronic-components/eeufc1e102/capacitor-1000uf-25v/dp/CA05156

 

https://www.rapidonline.com/suntan-ts13dj1e102msb0b0r-1000uf-25v-low-imp-electrolytic-capacitor-11-2924

 

2000uf

http://cpc.farnell.com/panasonic-electronic-components/eeufc1e222/capacitor-2200uf-25v/dp/CA05158

 

https://www.rapidonline.com/panasonic-eca1ehg222-2200uf-20-25v-105-c-radial-aluminium-electrolytic-11-2186

[Nick_]

Thing is, most commercially available stay alives, such as those available from TCS, are a hell of lot higher capacity than 2,200 microF. Think more in the way of 500,000 microF and also use super-Capacitors rather than electrolytics Which are a lot more expensive. I have one which will keep a loco running for over 30 secs at slow speed! Now whether 30 secs running time is actually needed is another question...

[Fishmanoz]

We are talking about 2 different products here, both of which are mentioned earlier in the topic.  For convenience and to match previous discussion topics, simple electrolytic capacitor types of around 2200uF have been called stay alives. Super capacitor types such as the TCS have been called keep alives.   Stay alives will usually only get you a second or two at most, enough to get past a dirty spot or points.  Keep alives go for much longer.

 

Stay alives can can be just the simple electrolytic mounted across the outlet of the decoder’s bridge rectifier, which is where the wires come from on products like DCC Concepts. With Chris ‘s explanation above, blue is the positive connection here but sometimes you have to find the negative yourself.

 

Keep alives, although they connect to the same points on the decoder, need more complex circuitry as SoT has described to limit the very high inrush current when  they are first connected.  The resistor does this and the diodes stop any negative overshoot.  Also, super capacitors are low voltage devices and you will normally require at least 2 in series to cope with the rectified DCC voltage.

 

You will need to decide what application you are aiming for to decide which is better for you.  If the answer is keep alive, then it will be a lot more expensive and you will need some expertise to assemble one yourself. 

[96RAF]

The other problem we have in describing these devices is we are using expressions that have been registered as trade marks, a bit like a Hoover is a hoover but a vacuum may not be a Hoover.

 

I believe Stay Alive is property of DCC Concepts And Keep Alive is property of TCS.

Rob

[Howbi]

We'll have to have our own 'registered name' in that case.........how about "Run-on Caps"(copyright HB).....other suggestions welcome........ 😆..........HB

[Nick_]

Can anybody confirm how far (or how long) a 2,200 microF capacitor will give With a loco running at a slow speed, but not a crawl?

I tried the stay alive supplied with a DCC Concepts zen decoder and at bes it appeared to keep the decoder alive for a few milli-secs and a few mm in distance, certainly less than the distance over a dead frog

[96RAF]

We'll have to have our own 'registered name' in that case.........how about "Run-on Caps"(copyright HB).....other suggestions welcome........ 😆..........HB

 

Keep-ya-going or dead-frog-jumper.

[Rog RJ]

The owner of DCC Concepts, Richard Johnson, says (on another forum) that the stay alive of the zen decoder is just to get the loco over small bits of dirt on the track or wheels, not to keep it going over dead frogs.  I think he also said that a new say alive is to be made available, which I think will be for the zen decoders as well as others, which will give longer run times over poor track and dead frogs.

[rpjallan]

DCC Concepts DCD-ZNSSA-1. I have one of these but I haven't installed it in anything yet. I believe it will keep a OO loco running for up to 2 metres. Their previous stay alives were more to improve very slow speed performance, which they do. I have a couple in a Bachmann Patriot & Jubilee which do not have pickups on the tender & they have certainly improve the low speed running of those locos...

[Reded]

Hornby TTS Class 31 Stay Alive...I posted here how to (plus some other neat info on this loco)

 

http://www.rmweb.co.uk/community/index.php?/topic/124592-some-rtr-rolling-stock-for-all-saints-east/page-2#entry3052551

[Reded]

Can anybody confirm how far (or how long) a 2,200 microF capacitor will give With a loco running at a slow speed, but not a crawl?

I tried the stay alive supplied with a DCC Concepts zen decoder and at bes it appeared to keep the decoder alive for a few milli-secs and a few mm in distance, certainly less than the distance over a dead frog

This depends on ther loco, how much its pulling, size of speaker etc...but you should expect at least a second with that, possibly more, which is what you generally need to cover dead spots. I use 680 - 1000mF in most of my locos unless they only have 2 wheel pickup and then I use between 2200 and 3900mF.

 

Do you have yours connected correctly ?

[Michael_A]

Stay alive. Keep alive. Doesn't matter, it's only about the capacitance.

 

At 12v, a motor drawing 100mA will discharge a 2,200uF capacitor in about 0.25 seconds. Useless. So a 22,000uF will be fully discharged in about 2.5 seconds. And will be too big to fit.....this is why you need super capacitors.

 

The trick is 3 x 1 Farad / 5.5v super capicitors in series, giving a capacitance of 330,000uF at 16.5v. This will take 40 seconds to fully discharge, so should allow your loco to run for at least 10 seconds.

 

https://www.ebay.co.uk/itm/2X-5-5V-1-0F-1F-Super-Capacitor-V-Type-Button-Smart-CapacitanceJ-C/192435589167?hash=item2cce0e102f:g:oMkAAOSwhIFZh8q-

 

Note you need 3, so order 2.

 

Then you will need a 100 ohm resistor in series to limit the charging current, and a diode facing back to the decoder to provide the backup power. Of course the polarity of the capacitors is also important

 

 

[Chrissaf]

The Super capacitor circuit that Michael describes, is featured as a drawing in a previous post of mine. See the third reply up from the bottom on the page.

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https://www.hornby.com/uk-en/forum/post/view/topic_id/13404/?p=2

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If you use Super Capacitors, you MUST use the resistor / diode protection circuit, else the inrush current (without the resistor / diode protection) could damage the bridge rectifier on the decoder.

[Michael_A]

The Super capacitor circuit that Michael describes, is featured as a drawing in a previous post of mine. See the third reply up from the bottom on the page.

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https://www.hornby.com/uk-en/forum/post/view/topic_id/13404/?p=2

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If you use Super Capacitors, you MUST use the resistor / diode protection circuit, else the inrush current will look like a 'short circuit' to your controller. The inrush current without the resistor / diode protection could also damage the bridge rectifier on the decoder.

My apologies, I hadn't realised you had posted that. Hopefully I won't be sued for copyright, clearly not an original idea so I can't patent it either!

[Chrissaf]

No problem Michael, I just thought a diagram that re-enforced what you wrote in text, would explain it easier to a novice not familiar with the concept of series wiring capacitors and maintaining capacitor polarity.