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Controlling uncouplers via DCC


Nick Ostrosky
 

I have a couple spots on my layout where I'd like to use remote uncouplers and didn't see what I was looking for in past posts here.  I've seen references about activating these through a DCC throttle rather than using an SPST toggle (e.g., accessory decoder like NCE SwitchKat) but unlike a turnout I thought I would need to leave the power on until I could separate the cars, so at least a few seconds.  The NCE manual I downloaded references changing the “ON TIME” of the decoder outputs but doesn't indicate any type of "maximum" setting.  Does anyone have experience setting this up and recommendations for appropriate settings?  Is there a downside to operating this through DCC (i.e., having it on for 10-15 seconds draining power from other operations)?  Thanks!


Paul O
 

Nick, the SwitchKat manual says that a CV can be set to a maximum of 255 (in milliseconds) which would give you about a quarter of a second of on-time max.
A momentary pushbutton switch wired to a separate power supply may be the best way to go. I believe those uncouplers have a pretty high current draw.

A DIY option would be a manual decoder, 555 timer, relay.

Paul  O


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wirefordcc
 

Hi Nick,

CVs in decoders have a maximum value of 255.  Of course, software for a particular CV may be lower.  You can experiment or contact Ed at NCE Tech support.  He's helpful and prompt.

Your remote uncouplers MIGHT draw more current than the decoder you choose to use.  I wasn't clear if you intend to use an accessory decoder or a loco decoder.  If you tried to use a loco decoder, you would have to select it first.  That wouldn't be convenient. Whatever you do, make sure your uncoupler doesn't stay on too long or it may overheat.  If it gets too hot, starts to melt, or emits smoke, you will know you went too far!

Allan Gartner
Wiring for DCC


whmvd
 

Maybe you could look at modifying the uncouplers to use servos instead? Much friendlier on current with so little load as an uncoupler causes, and no maximum duration. They only draw noticeably when something's actively working against them.

Wouter


On Thu, 8 Oct 2020 at 20:22, Nick Ostrosky <nick79ostr@...> wrote:
I have a couple spots on my layout where I'd like to use remote uncouplers and didn't see what I was looking for in past posts here.  I've seen references about activating these through a DCC throttle rather than using an SPST toggle (e.g., accessory decoder like NCE SwitchKat) but unlike a turnout I thought I would need to leave the power on until I could separate the cars, so at least a few seconds.  The NCE manual I downloaded references changing the “ON TIME” of the decoder outputs but doesn't indicate any type of "maximum" setting.  Does anyone have experience setting this up and recommendations for appropriate settings?  Is there a downside to operating this through DCC (i.e., having it on for 10-15 seconds draining power from other operations)?  Thanks!


Nick Ostrosky
 

Thank you all for your responses, it definitely sounds like this is better done with 12v DC.


Dale Gloer
 

Maybe I missed it but what type of remote uncoupler are you using?  At our club I have installed a number of KD Electromagnetic uncouplers.  We wanted to be able to push a button and have the uncouplers active for about 8 seconds.  These uncouplers draw a lot of current and leaving them on for too long will cause them to incinerate the coils.  I built a timing circuit using an LM555 for timing and a power Darlington transistor to switch the uncoupler power.  Note that these uncouplers require about 24 volts at 2 or 3 amps to operate successfully. The circuit worked but suffered frequent failures due to electronic noise cause by switching the power on and off.  I found a circuit that employed a relay and better design than my attempt on eBay for a few dollars each.  These work well and although we just use a pushbutton in the panel, they could be controlled by a DCC accessory decoder with a  couple of parts to interface them together.

Dale Gloer
Layout Supervisor at SAMRC


Nick Ostrosky
 

I was actually considering the Rapido Trains Railcrew uncoupler.  I've watched a couple install videos and these seem to be the better/easier option for retrofit in my situation.


Dale Gloer
 

Nick,

I have installed 3 of the Rapido Trains Railcrew uncouplers on my layout.  I was able to retrofit them into my existing benchwork and ballasted track following their instructions without having to remove the track.  They work very well although I found a little quirk.  If I have the uncoupler enabled and run a locomotives over the uncoupler it will no longer function.  I have to re enable the uncoupler.  Mostly this happens with some older Athearn locos.  It is caused by magnetic interaction with the loco and is due to the way the mechanism works.  Not a big deal, I just wait to enable the uncoupler until a loco has passed it.  The only downside to what you originally wrote is that they are not easily controlled by DCC without some wiring modifications.  If  you do modify the wring then I believe an DCC Accessory decoder that will operate Kato switch machines will operate the uncoupler (I haven't tried it).

Dale Gloer


Nick Ostrosky
 

Interesting.  I don't have any Athearn locos at the moment (Bowser/Stewart, a couple Overland, and a lone Bachman).  I would be interested if anyone else ran into similar problems with other brands, and will keep this in mind as I get into the install.  Thanks!


Swanny
 

Nick and Group, I've installed several dozen of these on the Cresson Branch, and find that overall they work well.  There are some quirks that they bring to the railroad, however.  Rolling stock with steel wheels and/or axles will cause the magnets to chatter as they pass over them.  This, of course, is most evident where the "pucks," as I like to call them, are installed on the main or through tracks.  Many locomotives will cause the rotational mechanism to release, as has been reported, but I don't find that an issue as my technique is to activate the device as the target couplers approach, and if it does release, a quick activation of the momentary-on-center-off toggle reactivates it.  Note that some steam locomotives which use a drawbar and pin coupling with the tender will uncouple if the drawbar is ferrous.  Although this will usually only happen going in reverse, it's unacceptable never the less.  My remedy is a small glob of DAP 235 caulk (anything similar will do) on the end of the pin, holding the draw bar in place but allowing for an easy disconnect if desired.  This fix has been working successfully through many operating sessions.
On the plus side, they are excellent at uncoupling cars only when desired, assisting in the successful uncoupling by providing a "spotting" LED, staying nearly entirely unseen, and only requiring normal 12 to 15 volt DC power with negligible current draw.  I had considered the idea of controlling a couple devices via DCC, but the need wasn't critical enough to push me into it.  I did have a brief chat with Mr. Dick Bronson of RR-Cirkits a few years ago, and although we agreed that we could probably use a MotorMan or other RR-Cirkits device, I never followed through.  I suspect that nearly any stationary decoder would easily handle the chore, due to their activation and deactivation with a momentary pulse, and requiring minimal current draw during the cycle and none once the magnets have rotated into or out of position.
I'd be happy to more fully share my experiences with these devices off line, or here within the group.
Stay safe.

John Swanson