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chris

Stay Alive

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Picked up a new DCC chip today. It's my first decoder from DCC Concepts and it has their Stay Alive module which is a clever little capacitor that keeps the loco moving (without stutter) when it passes over a bit of dirty track.

I've popped it into my new Cass 31 and given it a run up and down the sidings in the shed. First impressions are very good. It ran smoothly without any stutter or light flicker. I ran a DMU (with a TCS chip in it) around for a bit and and that proved that track was far from perfect!

The Stay Alive could be a very usefull bit of kit for DCC in the great outdoors.

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As long as it doesn't infect my sound decoders with dodgy music from the bee gees its a good idea.

Actually I must admit I already have some of these fitted to a couple of sound locos and they are very good.

I would go as far as saying if you want DCC sound in the garden then stay alive units are pretty much essential

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I've not gone down the sound route yet, but I have run a couple of my friends sound fitted loco's and I think you make a very good point.

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Can't say I've been impressed with the DCC Concepts Stay Alive, it doesn't appear to work :(

I've been doing some reading today about Stay Alive systems and the DCC Concepts one is not well regarded. TCS have released a Keep Alive range, but these are a bit pricy. It turns out that you can "roll your own".

A capacitor is enough, but a bit of current reduction from a resistor and a diode makes sense. They can even be added to DCC chips which aren't stay alive ready, if you're brave enough to solder directly onto the circuit board.

I'm going to have a dig around in my spares box and see if I've got any suitable capacitors hanging around and I may look at installing one.

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Digitrax uses a 330uF Capacitor on its SDH164D Sound decoder, which works very well IMO, but I think it is only for sound stay alive?

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george356 said:

Digitrax uses a 330uF Capacitor on its SDH164D Sound decoder, which works very well IMO, but I think it is only for sound stay alive?

So does the SDN144 range of sound decoders. Good decoders with excellent value, BUT they do seem very quiet when compared to other brands of sound decoder

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Does the stay alive on a sound chip keep the wheels turning or just the sound? I would asume it would be wheels and sound, but from what I've read 330uF is a bit on the low side. But seen as it works, I'm not complaining.

I'm thinking about putting a small capacitor on some of my function only decoders to keep the lights on.

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chris said:

Can't say I've been impressed with the DCC Concepts Stay Alive, it doesn't appear to work :(

I've been doing some reading today about Stay Alive systems and the DCC Concepts one is not well regarded. TCS have released a Keep Alive range, but these are a bit pricy. It turns out that you can "roll your own".

A capacitor is enough, but a bit of current reduction from a resistor and a diode makes sense. They can even be added to DCC chips which aren't stay alive ready, if you're brave enough to solder directly onto the circuit board.

I'm going to have a dig around in my spares box and see if I've got any suitable capacitors hanging around and I may look at installing one.

Chris, I am wondering what made you change your opinion between 5th January and 11th February? Your first impressions were very positive.

Two weeks ago I bought a Zimo MX644D Sound Decoder which came with a Stay Alive capacitor. Unfortunately there is not enough space in the 3F tender for the capacitor so I will be unable to use this feature. It would probably fit into most OO gauge diesels though.

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Sorry for the confusion, I've restarted this thread after a year so my opinion has been changed over a year of running. The loco with the stay alive didn't seem to perform noticeably better once out in the wild. I didnt do any proper tests (running into an isolated section) but my impression is that the stay alive isn't working.

Now I've done some reading about the subject, and I've found a 2200uF capacitor in my spares box, I'll have a go at trying my stay alive solution.

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I have a feeling, Chris, that using a 2200uF capacitor WILL give better running over suspect track, but I think it will be at the expense of moving off from a standstill (if my calculations are correct it will take a second or so to charge the capacitor, thus robbing the decoder/motor circuitry of power). I may be wrong, of course (and usually am) and I will watch this thread with interest.

BTW, what is the working voltage of the 2200uF cap.? - if it is close, but higher, than track voltage you may not notice any lag. If it is twice track voltage (normally 2200uf caps come in 10v, 16v, 25v & 35v) I think you WILL notice a lag.

I would be tempted to try a 16v 2200uf and experiment from there.

I know that ESU Locsound decoders use a 2200uF cap but I can't seem to find what working voltage they are.

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If my understanding is correct, then the charge up happens when the entire system is powered up rather than when the locos motor gets power. The capacitor needs a small current limiting resistor otherwise the current draw, across several locos, could be enough to trigger the short circuit protection.

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Ah, of course!! Doh!!

You are right, track voltage is constant therefore the cap will charge while you are assigning the loco number in your controller.

I wonder if a v large (physically) cap in a tender would allow running over a totally dead section, and for what distance?

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I read on some forum somewhere that a Lenz system, that costs the earth, can stay alive for 15 seconds on track which has been taped over. It can even change direction while on the tape, someone suggesting that it was picking up the signals electromagnetically.

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I had a go at a DIY stay alive this afternoon. It didn't work.

Too cold in the shed to have a go at troubleshooting. I'll have another try with the soldering iron sometime.

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chris said:

I had a go at a DIY stay alive this afternoon. It didn't work.

Too cold in the shed to have a go at troubleshooting. I'll have another try with the soldering iron sometime.

What did you try, Chris, to avoid others repeating your experiment (and failing too)?

If my memory of electronics is reliable (not always the case these days :lol: ), to charge up the cap from 15-18 v AC you will need to rectify the input to DC and have the capacitor as close in operating voltage as possible and be a high value ufarad, as we discussed previously.

The discharge path back to the motor is the unknown, IMO. Do you discharge through the decoder or directly to the motor? Hmm................ that is the question.

ETA - a little googling has found this

 - where the poster has found the decoder bridge rectifier and has soldered wires to the pads on the decoder board. He is able to apply 12v to these wires and drive the loco. I think that from this point he needs to use a voltage regulator feeding into a capacitor and he has cracked the problem, what do you think?

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The stay alive isn't on the AC side of DCC, it works on the rectified side of the chip.

The stay alive goes between the +DC wire (blue) and the ground. The ground doesn't usually have a wire and has to be found somewhere on the chip! I'm using DCC Concept's decoders that are Stay Alive Ready, and ready means they have two extra wires from the decoder to hook the stay alive to.

In theory a stay alive is just a capacitor. To stop a current rush into the cap at switch on a small resistor is placed on the positive feed. A diode is placed in parallel with the resistor to allow the current to by pass the resistor when it flows back.

post-6717-0-01161600-1331814552.jpg.d118b9f74670f757beeb99c5f8c9aad7.jpg

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I'd like to see the capacitor that keeps the house "alive" for 5 hours, Chris :lol:

I think you are within an ace of cracking the problem though, having the DCC Concepts decoder with the wires attached is a big plus. The probable fail point of your experiment will be the diode, probably gone open circuit, as you most certainly will have already figured out.

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I have a small battery pack (mini UPS) which is designed to give you 10 minutes of computer use when the mains goes down, enough time to save your work and shut down your PC. I have it in the shed and these days use it to power a light when I haven't switched the mains supply from the house on.

It's now in the study ready for the next outage. Broadband and wifi are plugged in to it. I can live without mains power, but not the internet :!:

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george356 said:

I think you are within an ace of cracking the problem though, having the DCC Concepts decoder with the wires attached is a big plus. The probable fail point of your experiment will be the diode, probably gone open circuit, as you most certainly will have already figured out.

Had chance to look into this today and your right, faulty diode.

I may try it with just the capacitor and see how that goes.

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