Hello!
Does anyone know the farads and voltage rating of Train Control System's KA2?
Thanks!
Dan.
Why not ask TCS? I don't think there will be any deep, dark secret about it.
Yes, the only thing proprietary about it is their label on the shrink wrap, the circuit is commonly published. Typical supercaps are about 5V, or 3.3V. I'd guess 3 in series for a 15V rating. Maybe 5 of the 3.3V ones for a 16.5V rating. Either plenty good enough for the typical HO track voltage of most DCC systems. Definitely not for O/Large Scale where the voltage is 20V or higher.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
A few sentences are nice but look at the below link and store the link in Favorites.
http://www.members.optusnet.com.au/mainnorth/alive.htm
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.
And scroll down, he takes them apart to look inside. Tha KA2 has 5x 2.7V 1F caps, which nets 200,000uF at 13.5V.
rrinker And scroll down, he takes them apart to look inside. Tha KA2 has 5x 2.7V 1F caps, which nets 200,000uF at 13.5V. --Randy
TCS's site indicates these are good to a maximum voltage of 16V. How do they compensate for the addional 2.5 volts over and above the total voltage rating of the five caps at 13.5 volts ?
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
That's a good question, capacitors do not like overvoltage, and supercapacitors are no different.
Mark R. TCS's site indicates these are good to a maximum voltage of 16V. How do they compensate for the addional 2.5 volts over and above the total voltage rating of the five caps at 13.5 volts ? Mark.
I could hazard a guess there's at least 1 diode dropping it to 15.3VDC...(Likely two dropping it to 14.6VDC)Then a voltage divider resistor series to keep the KA2s from sucking too many track amps.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
Well, they connect after the rectifier on the decoder, so there's 2 diode drops from track voltage, plus there is a single diode in the KA< along with a resistor, to limit inrush, so the caps can only charge up via the resistor, when they discharge to supply power, the decoder gets cap voltage minus one diode drop - on the Streamline Backshop web site he has a video demonstrating a keepalive connected to a Loksound decoder, not a commercial KA but the same type of circuit - the volume does drop when he disconnects the track power, but it keeps on making noise - at the very end it makes that typical dying electronics sound as the power from the cap drops below the level needed to keep the processor working.
Still, a 16 volt rating seems rather marginal. Not that long ago, I fabricated my own stay alive module using a 16 volt cap with the diode and resistor. It was attached to an old LokPilot decoder whose motor control was shot, but I just wanted it to control lights in a head-end car .... which it did. However, after about five minutes, that capacitor exploded, covering the interior of the car with yellow schmutz. Took me an hour to clean it up.
Replaced the capacitor with a 25 volt variety and has been working fine since. And for what it's worth, my track voltage measures 14.5 volts - and it still blew the 16 volt rated cap. Still scratching my head as to why ....
Thanks for the link! It is exactly what I was looking for, but could not find.
Aluminum electrlytic paste based caps alter chemistry and dry out over time. The don't hold the same charge as they age. I think the rough estimate is 10% loss over 5 years. There was a problem about 10 years back about exploding caps on motherboards because of this very reason.
http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx
When they rate power supplies for computers, you always notice how the warranties expire after 5 years. (Because they drop below total capacity and will likely click off if you push them to their rating.)
This was in most everything at tha time, not just computer motherboards - the manufacturers thought they were using top grade cpas but instead what they were getting were cheap counterfeits, lesser quality components marked as a high quality brand. Lots of electronics from that time have had failures that can be traced to either outright failure of the capacitor, or the cap not actually being the marked value and causing other circuit issues.
In quality gear, solid electronlytic capacitors have replaced the trastitional cans, up to certain values and/or in higher stress parts of the circuit. The better computer review sites, for example, will tear open a power supply and look at the quality of construction, including the components used. Little-known brands will get a black markBetter brands, and ones rater for higher than usual temperatures, for the traditional can type, get a bonus. The better power supplies do carry a full 5 year warranty, and when operated at a lesser load easily last twice that. There used to be, probably still is, a power supply calculation site for computer builders, one of the factors you could adjust for was capacitor lifespan. Want them to last longer? Use a slightly larger power supply so the max load is kept under 75%. Of course now we have 1200 and 1500 watt power supplies - which no one needs unless they are installing 3-4 video cards, but try telling some people that.