Stay Alive Capacitors

[Throppers]

Sorry to jump on the back of this but I'm hoping some will be able to answer my question re wiring a stay-alive to a TTS decoder.

I have a 1F stay-alive capacitor which I want to wire to a TTS decoder (yet to buy). I plan to wire the blue wire from the capacitor to the solder pad for the blue (common) for the decoder on the 8 pin plug. My question concerns the black negative wire from the capacitor. Does this have to go onto the rectifier bridge or can it go:

a) onto the black wire to the speaker

or 

b) onto the black wire solder pad on the 8 pin plug?

Many thanks. 

[Chrissaf]

Throppers,

Go back to Page 3 of this thread. The second post up from the bottom shows photograph of a TTS decoder indicating the 'stay alive' connection locations. It goes on the rectifier bridge, you will need a very fine tipped low wattage soldering iron and a steady hand.

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PS - Definitely NOT the two black wires you have indicated in your question a) & b). If you use either of these two black wires you will damage the decoder. Just because they are black, does not indicate that they are negative decoder power rail return voltage wires.

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1F (1 Farad = 1,000,000uF) is one hell of a 'stay alive' capacitor. In my view complete overkill. Great if you want to run the loco over a couple of feet of PLASTIC track. But seriously though, with a 1F capacitor value (assuming you have not purchased it as a manufactured 'stay alive' product and are making your own) you must include 'inrush' current protection in the form of a resistor / diode combination. A clickable link to a drawing is in the first reply on this this page of this thread. If you don't include the 'inrush' current protection you are likely to trip the 'short circuit' protection in the controller and at worst, burn out the rectifier bridge on the decoder, when you power up the loco from a fully discharged state.

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Did you mean 0.1F rather than 1F...........0.1F (100,000uF) would be more appropriate. Even 100,000uF (0.1F)  would be considered overkill. Some might say that even 10,000uF is overkill and use values of about 3,300uF. Anything above 10,000uF will need 'inrush' current protection fitted. More so, if 'Super Capacitors' are used. One feature of Super Caps is that they have extremely LOW internal impedance when discharged, they are in effect an electronic short circuit until they start to build up a charge.

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Also, remember that most SINGLE Super Caps have a LOW voltage rating, typically 5.5Volts. You need a 'stay alive' capacitor rated at a minimum 16 volts. Thus you have to series connect THREE Super Caps to get a 16.5 volt rating overall. Again, look at my drawing linked in the first reply on this page for details. If you put 16 volts across a 5.5 volt capacitor it will most likely swell up and go off with a bang. Capacitors have a voltage rating printed on their cases for a reason. The voltages are not advisory, they must be adhered to.

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Note: My supplementary comments in this reply are made for the information of ALL potential readers following this thread. So please don't think that I am 'teaching Grandmother to suck eggs'.

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[Chrissaf]

Throppers,

You have now used up your initial newbie 2 posts so won't be able to post again until tomorrow. The limit is there to protect the forum against auto-bot spammers flooding the forum with junk posts. The posting limit will be removed from your account in a couple of days.

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So in the meantime as a newbie, please be aware that I write long replies and the 'White Arrow in Blue Button' is not a 'Reply to this post' button. It can be distracting to keep repeating previous posters text in the yellow boxes unnecessarily. The correct 'reply' procedure is to scroll down to the bottom of the page. Write your reply in the 'Reply Text Box' and click the 'Green Reply Button' you will find there.

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....use the 66 quote tool icon in the reply box tool bar to turn it into a yellow box

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EDIT: It looks as if one of my ComMod colleagues has removed your reply due to the use of the Blue button. I assure you, I didn't remove it. I will still leave this reply in place just for your information. The removal has reduced your post count back down to 1 post. So you might be able to now post again today.

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[Throppers]

/media/tinymce_upload/dc53a25e8cba888b078216f5ce337d5a.JPGThanks Chrisaff for the advice. Will be sure to follow it re soldering the black wire to the right place. TTS decoder has been ordered so will compare it to the photos in this thread.

The stay alive is actuallly 7 x 1F 2.7V capacitors in series, which if I am working it out correctly is 142,000uf max 18.9V. I have had some issues with it in that the couple of decoders I tried with it seemed to be overcome by it and ran away even with DC running turned off in CV29. Anyway that has been sent back to the person I bought it from to check it out for me. 

Thanks for the tips re using the quite botton also!

[Throppers]

Thanks Chrisaff. The capacitor was made by someone else and bought by me. It's actually 7 1F 2.7V capacitors in series, which if my maths is right is 18.9V 149Kuf. 

My TTS decoder is on the way so hopefully using the info on this thread I'll solder the black wire to the right place!

I have had an issue with the capacitor in that when plugged into a decoder and the loco driven over an insulating tape to test it, it took off a lightening speed even with CV29 set to prevent DC running. Not sure if the issue is with the capacitor or the decoder so both have gone back to be checked/replaced. 

[Chrissaf]

The maths (capacitor values) is correct.

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It has been known for large value 'Stay Alive' capacitors (and yours are certainly large) to cause issues with decoders being programmed on the prog track. This is because very little current is available from the controller prog output. So when the decoder is being programmed (i.e reading / writing a CV) a discharged 'stay alive' capacitor is sucking all the available current, reducing the voltage on the decoder power rails and affecting its ability to correctly read and write the data.

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Therefore, it would be prudent to 'pre-charge' the 'stay alive' on the main track before using the 'prog' track. As long as the motor, lights & sound are 'off', then the capacitor should hold the charge long enough to allow programming activities to complete.

[Fishmanoz]

Can’t tell from the photos but does the unit include the essential resistor and diode or do you still have to fit them externally?

[Chrissaf]

I defy anyone to try and fit that one in a Class 08 TTS 😉

[Throppers]

"Can’t tell from the photos but does the unit include the essential resistor and diode or do you still have to fit them externally?"

Yes they are fitted but on the other side of the unit thus obscured from view. 

Chrisaff, re programming being affected by thestay-alive, I will try probraming the decoder without the SA attached and see if that makes a difference as previously I have always had the SA attached.

[david_lewsey]

I defy anyone to try and fit that one in a Class 08 TTS 😉

Funny you say that....digging the thread up from the grave here, but I have an 08 TTS which is fitted as standard I believe with a Loksound V4.....I need to fit a "stay alive" to the Loco, I don't want it to run for weeks by itself just enough to get over a dirty spot.

Is there any information for fitting SA into these chips?

[Howbi]

Either it is fitted with a Hornby TTS decoder or fitted with a Loksound, one or the other..........HB

[96RAF]

See here for how to fit a stay alive to a TTS decoder...

 

https://www.strathpefferjunction.com/adding-a-stay-alive-capacitor-to-a-hornby-tts-sound-decoder/

 

The TTS suffix means that it is fitted with Hornby’s in-house 8-pin sound decoder. Hornby first generation sound locos were suffixed XS and fitted with an ESU v3.5 or v4.0 21-pin sound decoder.

[ColinB]

What I did, was to use the instructions that RAF96 pointed you to, but instead of just adding a capacitor, I added a YouChoos "Stay alive circuit", it has a bit more protection than just a standard capacitor. I also found that you can read values in programming mode with it fitted, which you cannot with just a capacitor. It is fitted onto a Ringfield based Hornby HST 125 loco and it does make a difference. 

[Chrissaf]

The question raised by David Lewsey (bottom of Page 6 of this thread) is about fitting a 'Stay Alive' to an ESU Loksound V4 Sound Decoder, not a Hornby TTS decoder.

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David,

Go to this page and download the full ESU Manual for the Loksound V4 (download link is about 3/4 down the page).

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http://www.esu.eu/en/downloads/instruction-manuals/digital-decoders/

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Look at Manual Section 6.11 on Page 25 along with the drawings and text on Page 26.

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See also – further TIPs on how to get the best user experience from this forum.

https://www.hornby.com/uk-en/forum/tips-on-using-the-forum/

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[Rog RJ]

The information referred to by Chris

 

 

"6.11.1. LokSound H0, LokSound micro decoders 

You can connect two larger capacitors as per the circuit in the upper half of figure 14"

 

 

Figure 14 should be 24.

[Miss DCC]

So does the blue on the stay alive go to blue and the black wire go to red on the photo? Thank you

 

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.

 

[96RAF]

Miss DCC - you used the blue button to reply and your question has been lost in the repeated text from five pages previously.

As the repeated post contained a picture it was also held up all day for approval by site admin.

The answer to your question (top line of the repeated text) is clearly shown in the last paragraph of the text you quoted and is essentially NO.

I fear that if you are having trouble seeing that then the actual work of installing a stay alive may be beyond your skill set.

[Chrissaf]

So does the blue on the stay alive go to blue and the black wire go to red on the photo? Thank you

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Absolutely not. If you connect it that way the stay alive will swell up and possibly go off with a bang.

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Referring back to my photo and drawing...... I did add the last 'For the elimination of doubt' paragraph, so either that paragraph was not written with sufficient clarity on my part, or you failed to appreciate the significance off it.

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Decoders use a 'Blue' wire to denote the wire that has 'positive' potential. A poor choice of colour but that is what we are stuck with. Also, the 'Red' and 'Black' wires on a decoder are also not an indicator of voltage polarity, they are just wire colours that are standardised on a decoder and have no polarity significance.

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For the purpose of this thread, the stay alive that was being queried had 'Blue' and 'Black' wire colours. But one needs to confirm what terminal is positive and what terminal is negative on any 'stay alive' that you purchase.

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The positive of the 'stay alive' (a blue wire in this specific example) connects to the red cross on the photo. The red cross is also the same circuit location that the 'Blue' wire on the decoder is connected to. So in this instance, the 'Blue' wire on the 'Stay Alive' can be connected to the 'Blue' wire on the decoder. This probably accounts for the choice of 'Blue' wire colour on the 'stay alive' in this instance.

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Now for the 'stay alive' negative. A 'Black' wire in this specific example. The TTS decoder does not extend the negative of the decoder onto any wire. It is certainly not the 'Black' wire on the decoder. If you did connect the 'Black' wire of the 'stay alive' to the decoder 'Black' wire, damage will result.

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The negative (Black?) wire of the 'stay alive' needs to connect to the 'Blue' dash (negative symbol) in my photo. This location on the printed circuit board is the negative side of the 'bridge rectifier' that provides power for the decoder.

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Please note the TIP below: This is where your first attempt at replying went wrong. I also suggest reading TIPs 2 & 3 which explain how to extricate your reply text out of the buff quote box, which is what you did not do.

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TIP: As a newbie poster on the forum, just be aware that the 'Blue Button with the White Arrow' is not a 'Reply to this post' button. If you want to reply to any of the posts, scroll down and write your reply in the reply text box at the bottom of the page and click the Green 'Reply' button.

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See also – further TIPs on how to get the best user experience from this forum.

https://www.hornby.com/uk-en/forum/tips-on-using-the-forum/

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