[edit: This is not a question about using capacitors with decoders. It is a different application to see if capacitors can be used in a similar way to prevent drop out between power source and circuitry running at 12VDC]
I know that many decoders and decoder applications involve installation of a capacitor to prevent current drop out in spots on track, and keep the decoder functions, sound especially, active.
In the circuitry, are these capacitors installed directly in the pickup lead "from" the track "to" the decoder and thus providing continous current flow, or are they installed between the decoder and the speaker leads to provide the continuity?
And if the direct line from track voltage to the electronic device like the decoder, what rating of capacitor could be used between 12VDC track and a 12VDC mini amplifier if at all possible? Is it the same capacitor rating as used for a typical decoder on a 12VDC powered track?
Thanks for any tips.
Cisco KidIn the circuitry, are these capacitors installed directly in the pickup lead "from" the track "to" the decoder and thus providing continous current flow, or are they installed between the decoder and the speaker leads to provide the continuity?
Cisco:
I think that this should answer your question as to where the connections are: http://www.members.optusnet.com.au/mainnorth/alive.htm .
Hope this helps.
Joe
The capacitor is installed on the decoder, not the track pickups. The two leads connect to the main filter capacitor on the decoder.
SoundTraxx use to sell a first generation, LC decoder that used a bi-polar cap between one speaker lead and the speaker.
Google all this stuff and you will find many links.
Forget a capacitor for DC. When you reverse the loco direction, the polarity reverses which would blow the capacitor.
Also, bi-polar capacitors are not for storage like standard electrolytic caps.
This question pops up here every so often.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Not sure what exactly your are planning on running, but capacitors across the power input leads will provide a varied amount of "stay alive" depending on the value of the capacitor(s). Capacitors also are polarity sensitive, so, if you are running them off of DC track power, you must feed the track power through a rectifier to ensure the item you are running does not see reverse polarity. The capacitor(s) will be mounted between the rectifier and what you are running.
The rating should be greater than the voltage supplied. If you are using 12 volts, you should use capacitors with a rating of at least 16 volts, although I would recommend 25 volts if they fit.
Something else to keep in mind, the capacitors will only function as you expect if the input voltage is a constant to what you need. If you need 12 volts for your circuit, and the input voltage varies between 0 and 12 volts, the capacitors will not charge sufficiently to really do much of anything.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Thanks, Gentlemen.
After a little reading I see where the cap is installed on a decoder is rather more complex and needs to be on one side of the bridge rectifier. And in my application this system would not work at all. I have a work around using extra pickups though, so thanks for the tips.
BTW every time I try to access this link it does not work...just get the HTML text...does it work for you all?
http://www.members.optusnet.com.au/mainnorth/alive.htm .
Cisco KidBTW every time I try to access this link it does not work...just get the HTML text...does it work for you all? http://www.members.optusnet.com.au/mainnorth/alive.htm .
I just tried it and it works for me. Try typing it in and see if it works.
greg cited this Soundtraxx diegram in another discussion we were having, but it's useful here as it shows how the capacitor is hooked up with Tsunamis.
I do essentially the same thing with installs of 12 vdc LED light strip for car lighting. There's a bridge rectifier fed by DCC power pulled off the tracks with wipers. It supplies + and - 12 vdc. The capacitor is soldered ACROSS/between the + and - leads. This eliminates flicker and also provides for brief power interruptions, if your cap is big enough.
Mike Lehman
Urbana, IL
The link worked for me.
Original stay alive by Marcus.
Diode and resistor are important. The TCS and SoundTraxx stay alive have lots of capacitance and probably the diode and resistor. Never opened one. Much more than the 250 ufd included with the decoders. Rich
Diode and resistor are important. The TCS and SoundTraxx stay alive have lots of capacitance and probably the diode and resistor. Never opened one. Much more than the 250 ufd included with the decoders.
richg1998Diode and resistor are important. The TCS and SoundTraxx stay alive have lots of capacitance and probably the diode and resistor. Never opened one. Much more than the 250 ufd included with the decoders.
True. With the Micro-Tsunami diagram, you have the LEDs taking care of the diode and I think the Blue wire already has built in resistance, as it comes set-up to use LEDs, but I always add more resistance anyway.
One thing that's nice about how this is implmented is that it's easy enough to add a bigger capacitor with the Tsunami, if you have the room. My C-25 will be getting that upgrade when its decoder returns from its time-out in Durango.
mlehman richg1998 Diode and resistor are important. The TCS and SoundTraxx stay alive have lots of capacitance and probably the diode and resistor. Never opened one. Much more than the 250 ufd included with the decoders. True. With the Micro-Tsunami diagram, you have the LEDs taking care of the diode and I think the Blue wire already has built in resistance, as it comes set-up to use LEDs, but I always add more resistance anyway. One thing that's nice about how this is implmented is that it's easy enough to add a bigger capacitor with the Tsunami, if you have the room. My C-25 will be getting that upgrade when its decoder returns from its time-out in Durango.
richg1998 Diode and resistor are important. The TCS and SoundTraxx stay alive have lots of capacitance and probably the diode and resistor. Never opened one. Much more than the 250 ufd included with the decoders.
The blue wire has no extra resistance. It is connected directly to the positive side of the main filter capacitor. That is why it is called common.
The LED's do not have anything to do with the stay alive function.
A basic stay alive consist of an added capacitor, a diode, not an LED, and a resistor.
Commercial stay alive have super caps. Lots of capacitance in a very small package.
Isn't an LED a diode? It acts like one. Part of its name is "diode." Acts like a duck, quacks like a duck. I suspect that there's some economy of engineering going on with this Tsunami circuit.
I also know there is resistance built into the the TSU-750 backup light circuit, because I just confirmed that with Soundtraxx/Blackstone last week. At least the backup light worked as intended when I plugged one of those pricey SMD LEDs into a Blackstone C-19 TSU-750 installation when I installed a couple of those last week. I know the board is different than the aftermarket-packaged decoder, but I suspect there's resistance built in. Worth checking with Durango before you smoke that fancy new light emitting diode, though, don't take my word for it.
No, the LEDs on the lighting functions do not act as the diode in the inrush supression circuit. The other end of the LED connects tot he wrong part of the circuit - a function lead, which is after the control driver for that function output. Sure, ONE end is connected to the blue + wire - and if the decoder is set up with built in resistence for LEDs, then it's also the wrong blue wire for the keep-alive.
The other problem with using an LED for this purpose, LEDs have far too much voltage drop. Over 3 volts for a white one. An ordinary diode is .7 volt. Drop over 3 volts on the discharge of the capacitor and you will see a huge change in loco speed, and it will still be jerky (but not stall) on dirty track. Kind of defeats the purpose.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Randy,
OK, I'll buy that about there being too much V drop in a LED. I was interpolating as best I could, not know what's going on in the black box...err, purple box...at the center of the circuit.
Does bring to mind, is there a better way to hookup the keep alive cap circuit to a Tsunami? I'm guessing the way Soundtraxx did it works...or does it?
The resistor and diode are only in a stay alive circuit to slow down the inrush current to the capacitor. With some DCC systems, a high inrush of current could be detected as a short to the system. The resistor limits the inrush of current and the diode bypasses the resistor when the capacitor discharges.
The green / yellow wire on the Tsunami connects to the negative side of the onboard rectifier. The small 220mf rating of the capacitor doesn't require the additional resistor / diode due to its small capacitance. Aftermarket stay alive modules have capacitance approaching 1 farad - which is a LOT more capacitance (1 farad = 1,000,000mf), and thus a sizable inrush of current.
It would take some experimenting to determine the line of capacitance between needing and not needing the diode and resistor. It would probably be determined by when you system sees that inrush as a short.
Mark,
OK, that makes sense. I have about 20 of the 470 uF caps in various passenger cars and haven't had the system puke yet on me.
Blackstone passed me an extra one of the 220 uf caps some time back so I could double up the cap on one of my units. I'm guessing just subbing the 470 should work fine in place of 2x 220 uF, as it's pretty darn close to their 440 uF total.
The way Soundtraxx hooked it up, it only serves to keep the sound on, NOT the motor. The diagram from Marcus's site is the way to hook up a Tsunami and get keep alive for both the sound and motor, though it is not going to last as long as the add-on supercapacitor keep alives. Marcus's circuit can be applied to any decoder where you cna find the proper connection points. The super capacitor keep alives like the TCS one, or the Lenz one, have enough storage energy to keep the motor going for mny seconds. If your tracka nd wheels are clean, the smaller stuff should be fine. If you have long dead spots, then you need the super cap type of keep alive.
Generally, my C-class locos tend to be light-footed. My K-28 and K-36 and the diesels do OK. I'll look into Marcus' circuit, but plain old caps should do the trick with the C-25, as there's plenty of room. The C-19s are a bit more cramped, because Blackstone spreads the Tsu-750 out on a circuit board mounted in the tender, rather than encased in shrink.
The caps on the are integral to the board, rather than being a separate component as supplied with the aftermarket -750. They appear to be those button-type caps that are used to protect memory in a lot of devices nowadays and arr mounted side by side in the middle of the board. I'm thinking leave them alone for the soound and just add capacitance off the board.for the motor. On the other hand, if its not obvious, I'll be back looking for some help.
Cisco Kid [edit: This is not a question about using capacitors with decoders. It is a different application to see if capacitors can be used in a similar way to prevent drop out between power source and circuitry running at 12VDC] Thanks for any tips.
First off, DCC track power is AC and not DC. Capacitors act like a short to AC, so you can not connect a capacitor directly to the track. If you want to use DCC track voltage, (not a good idea anyway) you must turn it into DC by rectifying it with a diode or bridge rectifier.
To store DC energy, the capacitor has to be conneced to the source, or the DC input to the device that you want to use, from plus to minus. If your source is 12VDC, the working voltage of the cap can be 12VDC, but I would recommend twice the voltage you are using. As far as the capacitance value, the highter the better.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
Mike, Were you sucessfull in your attempts to add capacitance to the Blackstone C-19?