# Capacitors



## bcer960 (Dec 27, 2007)

This goes out to all the DCC guru's. I am thinking about building a very small car with the wheel base about 3 scale feet. I am planing to run it on a DG123. What I am concerned about is as this car goes over a switch or dirt it will lose contact and stall. Has anyone used the capacitor/resister to carry current until it can establish contact. I know this works in DC, how about DCC??
Thanks

Ray


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## Greg Elmassian (Jan 3, 2008)

Yes, common practice in DCC, especially in the smaller scales. I prefer a decoder with special provisions for the capacitor. Normally you will have to provide an on off switch to take the capacitor out of circuit to use the programming track, kind of a pain. 

But, I recently used a new Zimo 642 HO decoder in 2 locos, a "Walt Disney Casey Jr" and a Berlyn rail truck, and the decoder is smart enough (I guess) disconnect the capacitor when programming... very nice. (It is a 1 amp HO decoder that handles a peak of 2 amps and is very small)... It's motor and sound... not just a motor decoder. 

They also have a "galloping goose" sound file that is really fun and has the putt-putt sound and gear shifting of 4 speeds... You can see this on my site under Zimo, and also under the Berlyn Rail Truck under "motive power"... 

Regards, Greg


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## steam5 (Jun 22, 2008)

The lenz gold decoder has this feature. You need to purchase the decoder and the power module. This system will also allow you to control the loco over the dead spots, not just get it over it.


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## Trains West (Oct 4, 2008)

I have used the gold decoder and it works very well you can use the power three with the HO decoder if it is low draw on the motor


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## bcer960 (Dec 27, 2007)

Thanks guys, 

I will look inti the lenz decoder.

Ray


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## Cougar Rock Rail (Jan 2, 2008)

You can also use any of the Massoth decoders...they also sell capacitor units that plug into their boards. The decoder monitors the charging and allows you to program as well. 

Keith


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## George Schreyer (Jan 16, 2009)

I've done this with a DG580L some time ago. It worked, but the newer decoders work well enough on the same cruddy track in the same loco WITHOUT the capacitor. 

Try it first, then cut into it if you have to. 

http://www.girr.org/girr/tips/tips5/dcc_tips.html#dirt


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## Dan Pierce (Jan 2, 2008)

Zimo decoders have a provision for a capacitor on the sound circuit that does not other the programming, but a capacitor on the track DC needs a disconnect switch (esp the MX69 series).


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## Greg Elmassian (Jan 3, 2008)

Dan, by "track DC" you mean after the full wave bridge has rectified the DCC track signal? 

If so, every decoder with a capacitor so connected needs a disconnect switch for use on the programming track. 

I think the Zimo capacitor is on the microprocessor power bus... but that's my guess... 

Greg


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## Tom Bray (Jan 20, 2009)

I think you need the disconnect if you want to rewrite the sound file but programming is not an issue. I know Axel told me to put the switch in. I put the capacitor bank across the 22V line. It is also possible to put it across the section just related to the sound so that they keep running after the power interrupts it. 

Tom


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## Dan Pierce (Jan 2, 2008)

Greg, the Zimo sound decoder has a capacitor (4700uf 25WVDC minimum) only for the sound on the speaker side pin 9 (5 volt audio), it is installed without other components. 


For all series MX69, on the positive supply, you need to add a capacitor, diode, charging resistor choke and a bleeder resistor.


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## bcer960 (Dec 27, 2007)

Just wanted you guys to know that I am still here, just sitting back and listening. I am somewhat new to DCC, only been using it for a couple of years, and have all Digitrax. So all info about other brands is very interesting. 
Whatever the best decision is, I plan on using it for 2 "cars" First is a speeder that I want to model this winter after my MT-19, the wheel base will be less than 1 1/2". The second in a die cast car. Wheel base about 5". But both of these are only 2 axels, so I am anticipating problems at switch frogs. 

George , I have been to your site many times over the years and found the DCC speeder page very interesting. 

Thanks to all 

Ray


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## Greg Elmassian (Jan 3, 2008)

Dan I run 24v DCC, so 35v is what should be used in my case (that's typically the next voltage increment available). I have a Zimo 642, and the manual, and used a 1000 mfd on that one... but of course that is a different decoder... it's pretty clear in this case the capacitor is running on rectified track voltage, but I would guess there is the diode/resistor combination somewhere. 

Which decoder are you talking about in your last post, I'm a bit confused: 
"Greg, the Zimo sound decoder has a capacitor (4700uf 25WVDC minimum) only for the sound on the speaker side pin 9 (5 volt audio), it is installed without other components. " 

Does that sentence mean some decoder OTHER THAN the MX69x series? A 25 volt cap on a 5 volt line? Wow. 

I understand this sentence: 
"For all series MX69, on the positive supply, you need to add a capacitor, diode, charging resistor choke and a bleeder resistor." 
Yes, as I stated, this is true for ANY decoder if you are trying to fit one after the FW bridge. 

Regards, Greg


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## StanleyAmes (Jan 3, 2008)

Ray 

For your application I would really recommend using a Lenz Gold decoder with a supercap power module. The reason for this recomendation is that there is a big difference between adding a capasitor to a decoder and having a decoder designed with a power module. The Lenz decoder will have nearly 100% packet reception even when you are on a plastic fron or on dirty track. 

I wish more manufacturers would impolement something similar because of the big difference in operation such a hybrid approach provides. 

Stan Ames 
http://www.tttrains.com/largescale/


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## Dan Pierce (Jan 2, 2008)

We buy capacitors in quantity and are currently only trying to stock 35 volt units so no one would put an under rated cap in any track related power circuit. 

It never hurts to have a higher voltage rated capacitor in any circuit and smaller voltages just give a smaller physical unit. 

I large scale, you usually are not concerned with the differences in capacitor physical sizes, but voltage ratings are important, so we are using 35 volts as the standard for all filter capacitors. 

PS, we used 10,000 mfd on the MX640 units.


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## Greg Elmassian (Jan 3, 2008)

Sounds like a very smart plan. I had to use a 1,000 Mfd on the 642 Zimo because I am using it in 2 very small pieces of rolling stock, a Berlyn rail truck, and an Accucraft "Casey Jr" whimsical locomotive. (That's why I had a HO decoder in the first place). 

Regards, Greg


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