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Post by nebrzephyr on Nov 19, 2014 11:58:14 GMT -8
So, I'm guessing these are just a series of smaller capacitors wired together. Does anyone know what the total uf rating of these are? I ask because I assume if one had the space in the loco you could just replicate the function with a larger standalone capacitor. Or is there something unique about these devices?
Thanks. Bob
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Post by Mark R. on Nov 19, 2014 15:11:58 GMT -8
The unique aspect is their physical size. They accomplish this small size by using low voltage ratings and wiring them in series. TCS uses 3.5 volt caps. Five of them in series gives them a working max voltage of 17.5 volts. The super-caps are rated for 1 FARAD, which when wired in series gives a total capacitance of 200,000 Mfd for the five caps. A single capacitor with a rating of 200,000 Mfd at 16 volts would be a pretty large capacitor physically.
Mark.
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Post by nebrzephyr on Nov 19, 2014 16:56:42 GMT -8
Mark....thanks for the insight on these things. I guess the caps they use are not the kind we modelers would typically have access to.
Wired in "series"......guess that's a little confusing. Thought it needed to be parallel to be additive value. Oh well, should have known it wasn't as simple as substituting an "off the shelf" cap.
Bob
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Post by nebrzephyr on Nov 19, 2014 17:29:31 GMT -8
So then the next question. Could one take a "poor man's" approach and hook up a typical capacitor in the same manner as the current keepers to get a small "keep alive", admittedly much less than the commercial products. Much like the approach Soundtraxx uses on its Tsunami. Hummm...
Bob
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Post by Mark R. on Nov 19, 2014 20:23:55 GMT -8
The capacitors used in stay alive modules are called "super caps" and commonly used as storage devices in computers. They are readily available, but their voltage ratings are normally lower than what we use and their capacitance is huge in comparison. When wiring capacitors in series, you add the voltage rating of each to get the total voltage rating of the group. However, the capacitance is fractional by the number of capacitors in series. That's why they use 1 FARAD (1,000,000 Mfd) capacitors .... five in series would end up being 200,000 Mfd. (which is still a good amount of capacitance. Capacitors wired in parallel would be the total capacitance added together of each, but the voltage rating would remain constant (if both / all caps are rated the same), or the voltage rating would be the lowest rated voltage for the capacitors in the circuit (a 50V and a 20V in parallel would net a 20V working voltage max). The capacitor on the Tsunami is strictly a stay alive cap for the audio portion of the decoder. This prevents the sound from resetting every time your engine hits a speck of dirt. It is not connected through the motor control circuit. Most any 16V rated standard capacitor that would physically fit in your engine wouldn't provide even a noticeable amount of stay alive for your motor and lights. There's a reason why the manufacturer's are making them the way they are .... they work. If there was a poor man's approach that actually worked, somebody would already be making a cheaper version. Something else to keep in mind - most systems will not program a decoder with a stay-alive module attached. It has to be disconnected (either physically or through a switch) to program, then be re-connected to run. Lot more information here .... www.members.optusnet.com.au/mainnorth/alive.htmMark. |
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Post by nebrzephyr on Nov 20, 2014 6:49:42 GMT -8
Mark....oh, I was missing the "voltage" aspect when thinking series vs parallel. I had in mind capacitance.
"Something else to keep in mind - most systems will not program a decoder with a stay-alive module attached. It has to be disconnected (either physically or through a switch) to program, then be re-connected to run."
Interesting. On the 2 Soundtraxx CurrentKeepers I have installed I had no problems programming on the programming track - Digitrax + Soundtraxx "Booster".
Thanks again for the info. Bob
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Post by Mark R. on Nov 20, 2014 18:57:33 GMT -8
The only times I've been unable to read / write decoders with the TCS KA2 installed was when they had a charge to them. I found more often than not, if I fully discharged the capacitor, then went straight to the program track, they would work almost every time. If the capacitor is charged, it will be supplying power to the decoder which will cause the command station to not interpret the read-back sequence correctly.
I've only had two cases out of many, where it just plain would not work without dis-connecting it. For those two, I installed a small micro slide switch behind the front pilot to cut the stay alive module in and out of the circuit.
Mark.
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Post by nebrzephyr on Nov 21, 2014 6:16:28 GMT -8
Thanks Mark on the "charged" aspect.
Question. Do you have any idea on how to find the "negative" power point on a typical decoder? Say an Athearn RTR or Genesis light board. I know there must be a way but I don't have enough electronic experience to know how. Thanks. Bob
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Post by Mark R. on Nov 21, 2014 11:38:16 GMT -8
The very first section in the link I provided you with earlier describes where to find the negative connecting point on all decoders.
The stay alive module is not connected to the light board (won't work on DC) - it is connected to the decoder. If you are using the factory light board which has the 8-pin / 9-pin plugs, the decoder attaches to the plug and the stay alive module is soldered to the decoder itself.
Mark.
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Post by nebrzephyr on Nov 21, 2014 14:26:02 GMT -8
Thanks Mark.....on the link, I didn't scroll far enough down on the page. Bob
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Post by Mark R. on Nov 21, 2014 14:38:08 GMT -8
No scrolling required Bob, it's the first thing you see when you open the page.  Mark. |
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Post by flanker on Jan 12, 2015 3:03:32 GMT -8
you can buy super caps from Ebay, they cost like 1 doller per cap, I made my own keep alives with them costed me like 3.5 dollers per locomotive very cheap comparing to what many professional offers are out there.
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Post by gmpullman on Jan 15, 2015 8:26:00 GMT -8
you can buy super caps from Ebay, they cost like 1 doller per cap, I made my own keep alives with them costed me like 3.5 dollers per locomotive very cheap comparing to what many professional offers are out there. I bought mine here: Ebay SupercapsHope that helps... Ed |
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Post by riogrande on Jan 15, 2015 9:43:50 GMT -8
I've never heard of super capacitors before but back when I took electronics in college and built more circuits we used something called electrolytic capacitors which AFAIK worked the same way.
Is super just a re-branding or renaming of the electrolytic type or are they somehow different?
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Post by Mark R. on Jan 15, 2015 14:48:20 GMT -8
I've never heard of super capacitors before but back when I took electronics in college and built more circuits we used something called electrolytic capacitors which AFAIK worked the same way. Is super just a re-branding or renaming of the electrolytic type or are they somehow different? Two different animals in their structure. The super caps have a MUCH higher capacitance than an electrolytic capacitor of the same physical size. Much like how they are making batteries with considerably larger / longer storage capacity, capacitors as well are benefitting from new technology. They have to make those smaller / thinner electronic devices work longer with smaller and smaller devices. A 1 farad super capacitor is about the size of eight pennies stacked .... a 1 farad electrolytic capacitor is the size of a pill bottle .... Mark. |
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Post by riogrande on Jan 15, 2015 16:30:25 GMT -8
That makes sense, hence the name! I'm a bit rusty but it's starting to come back!
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Post by flanker on Jan 16, 2015 9:32:51 GMT -8
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