Disconnecting capacitors for the purpose of programming.

[craigolio1]

I was reading Tim’s RS3 thread and he mentioned the capacitance of 440uf being high enough that it can affect programming and that it might have to be disconnected. I’ve heard of this before.

Several of my locos have complicated wiring inside for lighting and I wonder if it would be useful  to be able to disconnect the caps with out taking the shells off.

First I thought of running one cap wire under the fuel tank so I could access it and disconnect. But then I thought could a decoder be used for this?

Could one function be used to activate an NPN transistor that would then allow the pos blue wire feed of the cap to pass through? There for allowing the capacitance to be disengaged electronically?

Craig.

[RBrodzinsky]

I don’t see how, but may be wrong. The issue is programming with the LokProgrammer. So, you don’t have active DCC signal to control the output on the decoder (or secondary one).  With HO and larger, some folks have added a micro switch. I’ve never thought about routing the wire (personally I would do the decoder ground) down to the fuel tank and milling out space there for a micro switch

[carlso]

I do not have an answer, but I will throw out a question for the "teachers". Wouldn't it be easier to add one of the small chokes into the caps wiring harness ?

[peteski]

No need to get that fancy Craig (plus, since the current flows both into and out of those caps) a transistor would not work.

Much simpler solution is one I mentioned in https://www.therailwire.net/forum/index.php?topic=45273.msg586258#msg586258. ZIMO decoder manual shows some sample diagrams.  A coil resists change in electric current. It blocks the short programming current pulses from reaching the caps.

In some instances a resistor and diode also work: https://www.therailwire.net/forum/index.php?topic=43101

ZIMO decoder manual can be downloaded at http://www.zimo.at/web2010/documents/MX-KleineDecoder_E.pdf.  The sample keep alive hookups are towards the back of the manual (around page 60).

[Steveruger45]

I’ve installed choke (inductor) to fix this on ESU 73800 and it works.
See https://www.therailwire.net/forum/index.php?topic=45354.msg587453#msg587453
Just wire the choke in series with either positive or negative wire going to the caps.  I tend to favor the positive by preference but it doesn’t matter which side in a series circuit.

[craigolio1]

The inductor definitely sounds less complicated

 Craig

[nstars]

For the lazy people there is the Zimo SACC16 which has the necessary electronic on a PCB.

Marc