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Thread: Capacitors for DCC stay alive

  1. #1

    Capacitors for DCC stay alive

    Lately Iíve been studying up on using capacitors as energy storage backup for DCC. This is just going to be a catch-all for info I have found. Itís an interesting topic that I canít seem to find a whole lot of information about.

    First, ts useful to understand how capacitance is measured. 1 farad is equal to 1,000,000 micro farad, or uf. So if a capacitor is rated at 0.1 uf thatís 100,000 uf.


    This is the DCCwiki article: http://www.dccwiki.com/Energy_Storage


    Next another article showing some different types: http://www.members.optusnet.com.au/mainnorth/alive.htm


    Types of capacitors include:


    Electrolytic capacitor- this is the basic type of capacitor that is included with Soundtraxx Tsunami sound decoders (220 uf). Useful for keeping sound decoders from resetting. Even in the 4700 uf range, can only supply backup voltage for a fraction of a second.


    Tantalum capacitors- these are compact capacitors, typically around 7x4x4mm. Can be wired together in parallel to form a compact package. Handy for installations where electrolytic caps are too large, but a small amount of capacitance is still desirable.


    Double layer, gold, super capacitors, etc- these capacitors have lower voltages, but much higher capacitance. These are what TCS uses for their keep alives. For example the KA1 uses 6 X 220,000 uf super capacitors at 2.5 volts each, wired in series, for a total keep alive capacitance of 36,667 uf at 15 volts.
    The KA1 provides a whopping 200,000 uf at 13.5 volts.


    So anyway, thatís what Iíve dug up, without doing any actual experimenting myself. Iíd like to hear from anyone that has some experience with stay alives, what kind, what capacitance and the results. Iíll post my own results here from time to time.

  2. #2
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    Lots of info in the below article.

    http://www.members.optusnet.com.au/mainnorth/alive.htm

    I and many others use the standard electrolytic. Some also use SMD caps.

    Rich

  3. #3
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    Stay Alive.

    Pay attention to the TCS products.
    Lost of discussion going on in some of the Yahoo DCC Groups.

    Rich

  4. #4
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    There is also the S-Cab BPS system, which can be used with standard DCC controlled locos (and their RC/DCC system).



    In this picture the battery is not shown, it plugs into the white plug on the bottom right of the Battery Power System board. Using this you eliminate studder at turnouts and dirty track. You are only limited by losing the DCC signal, which the S-Cab RC system bypasses. I am DC right now and am considering going with S-Cab when I get my layout finished.

  5. #5
    It will be interesting to see how these "super capacitors" work out for model RRing apps. I know them as MultiLayerCeramic (MLC) capacitors and they have been around since at least the early 1980s. Early on they had tremendous reliability problems which were due to handling problems and not materials wear out problems. The gold refers to the end contacts of the MLC "mini-brick" and not the interior metallurgy. Gold contacts are mil-spec devices and are more expensive than the commercial Sn contacts (tin over nickel). They are usually wired in parallel to provide filtering circuitry so that if one does fail the rest of the bricks "carry on". Wired in series means thatif one "cracks" the circuit is kaput. My feeling is that if they make it through the first few hours of operation w/o failure they will last a lifetime. Good luck to us all. By the way..these MLCs are really cheap. As more decoder mfrs. pick this technology up I would hope prices would at least stabilize if not come down a bit. You always (and should expect) new technology to bring premium prices at the gitgo...but as more mfrs. pile on I'm hoping for the best.

  6. #6
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    TCS products, Keep Alive modules are the going item for Stay Alive. Seeing this in a bunch of DCC forums.
    One issue I am seeing. Good stay alive will keep a loco going, even if you try to stop with the controller, Stop switch. The on board circuits are still getting power from what is stored in Keep Alive caps. Sometimes long enough to hit an open switch or another train.

    Rich

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