Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

Hard Wiring a Decoder

879 views
21 replies
1 rating 2 rating 3 rating 4 rating 5 rating
  • Member since
    December, 2015
  • 1,907 posts
Hard Wiring a Decoder
Posted by BigDaddy on Sunday, September 10, 2017 6:27 PM

I don't spend time on any other forums. Somewhere I saw a blurb about using a circuit board tie as a soldering pad for installing a decoder.  Maybe it was here, probably it was MR or a Youtube video.  The accompaning photo was poor so I realy couldn't see much.

I have a LL GP-7 and a loksound select micro decoder with an 8 pin plug.  I had planned to cut the plug off.  I also have a circuit board that I bought a gazillion years ago that could substitute for a CB tie.

I think that heat shrink tubing, even very small tubing is inflexible and somewhat clunky to deal with.

The Question is how best to connect the wires?

1) Using a piece or two of circuit board

2) Placing the wires side by side pointed in opposite directions. I have had no luck twisting small wires together.  Helping hands help or bending a U shape into each wire helps but it's delicate work.

3) Side by side in the same direction.  I've not actually done it this way, but it would be easier to twist the wires together.

I'm newer than Gary in dealing with DCC and would appreciate the advice of those who have done it more.

 

 

 

 

Henry

COB Potomac & Northern

By the Chesapeake Bay

  • Member since
    February, 2002
  • From: Reading, PA
  • 22,657 posts
Posted by rrinker on Sunday, September 10, 2017 6:52 PM

 I just use heat shrink and a linear, Western Union-style splice. The twisted wire holds well enough to solder - the key is a clean soldering ron so you don;t have to press hard. I don't hold the wire in a helping hands or anything, just press the iron to one side of the joint and the solder to the other, in a second or so the solder flows and it's done. Don't forget to put the heat shrink on BEFORE soldering (don't ask). The small heat shrink works very well - typically you can't get small enough stuff at the big box store, you need to find it in a hobby shop or electronic shop _ think I picked up the supply of smaller sizes I have at a train show.

 Ends up like this: (and I have vision issues and not the best of fine motor skills)

 

 That's exactly a P2K GP-7. One resistor for the LED is there witht he wires, the one for the short hood light is under the decoder.

                               --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    January, 2010
  • 1,854 posts
Posted by peahrens on Sunday, September 10, 2017 6:56 PM

It was a progression for me.  I did my first conversion from DC with a motor only plug in decoder for a Kato DCC ready RS-2.  I did my first board replacement decoder for a Genesis Tsumami w/sound GP9 with a LokSound Select Direct, the version with a circuit board replacment. 

Since then, I've happily taken the advise of some others here to rip out the original circuit boards (on DC locos light boards that may include a DCC ready plug).  I cut off the 8 pin connector and cut any unneeded wires real shoty.  For me that accomplishes two things.  First, it makes things simple, as I do not need to understand the pre-existing circuti board.  Two decoder wires to the rail, two to the motor, others to lights (front, reverse, ditch). Second, it provides valuable room for decoder and speakers.  I usually add my own micro speakers (usually 2 or more) and I can optimize the space for a larger enclosure, which helps speaker performance.  I use the Select 6Aux usually (sometimes the micro), which in diesel usually rests nicely atop the motor where the old circuit board was.  I use Scotch tape to secure the decoder and wires atop it.

One caveat, is to pay attention to any pre-existing lighting.  I often take out existing bulbs and add LED lights with an appropriate resistor.  Note that some DCC direct replacement boards may include the resistor, so you need to understand that.  If re-using existing bulbs, you need to understand they are 12v, 1.5v, etc and how that relates to your decoder.  It is rather preferable to replace bulbs with LED lighting so as to preclude (depending on your life expectancy) burnout of the bulb and related maintenance.  Please don't replace a burned out bulb with a bulb. Confused

For connecting wires, I don't bother trying to twist them together, and do not see a need to use a circuit board piece for the connections.  I generally connect the wires in parallel end to end, just overlapping at the stripped wire ends.  Importantly, I tin the wires first and then just hold them together and solder them with a wet tinned tip.  Flux helps, I think.  After the solder cools, give a tug to test the connection.  I use the typical shrink wraps, keeping the various small sizes on hand for the small wires.  For the rail leads, from two trucks, I solder them to each other and the decoder lead, requiring a split in the insulation along the length to create a "wye" connection point to the truck.

 IMG_6232 by Paul Ahrens, on Flickr

Hope this helps.  After a few projects, it becomes pretty easy.

Paul

Modeling HO with a transition era UP bent

  • Member since
    January, 2009
  • 2,069 posts
Posted by RR_Mel on Sunday, September 10, 2017 7:39 PM

I went with wiring harnesses for my diesels and the 8 pin connectors for my steam.
 
Check out my blog post on my E7s.
 
 
 
I would think all decoder manufacturers sell wiring harness for their decoders.
 
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
 
  • Member since
    November, 2013
  • From: Ledyard, CT
  • 1,702 posts
Posted by BMMECNYC on Sunday, September 10, 2017 7:55 PM

rrinker

 I just use heat shrink and a linear, Western Union-style splice. The twisted wire holds well enough to solder - the key is a clean soldering ron so you don;t have to press hard. I don't hold the wire in a helping hands or anything, just press the iron to one side of the joint and the solder to the other, in a second or so the solder flows and it's done. Don't forget to put the heat shrink on BEFORE soldering (don't ask). The small heat shrink works very well - typically you can't get small enough stuff at the big box store, you need to find it in a hobby shop or electronic shop _ think I picked up the supply of smaller sizes I have at a train show.

 Ends up like this: (and I have vision issues and not the best of fine motor skills)

 

 That's exactly a P2K GP-7. One resistor for the LED is there witht he wires, the one for the short hood light is under the decoder.

                               --Randy

 

 

This is how I do my installs now (if there is no plug).

Rule 108: In case of doubt or uncertainty, the safe course must be taken.
  • Member since
    February, 2002
  • From: Reading, PA
  • 22,657 posts
Posted by rrinker on Sunday, September 10, 2017 9:11 PM

 Those things have plugs. And 3V light bulbs. Both come out.

                         --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    July, 2006
  • From: Bradford, Ontario
  • 7,481 posts
Posted by hon30critter on Sunday, September 10, 2017 10:45 PM

Paul and Randy:

Nice clean installations.Yes Excellent examples for the OP.

Dave

  • Member since
    July, 2006
  • From: Bradford, Ontario
  • 7,481 posts
Posted by hon30critter on Sunday, September 10, 2017 10:58 PM

BigDaddy
3) Side by side in the same direction.  I've not actually done it this way, but it would be easier to twist the wires together.

That works fine if you are having trouble getting the wires to stay together. I have done it many times. The wires have to be a bit longer, but in my experience having a bit of extra wire is a good thing. One advantage to using this method is that you can clip off the excess joint so the amount of heat shrink required is smaller. You only need about 1/4" of soldered connection for it to be plenty solid enough. 

BigDaddy
I think that heat shrink tubing, even very small tubing is inflexible and somewhat clunky to deal with.

I have never had a problem with heat shrink tubing not being flexible enough, but there are different varieties of tubing. I have some older stuff which is very shiney and it is rather rigid. The more recent stuff flexes easily.

BigDaddy
Using a piece or two of circuit board

I'd be interested to see how a piece of circuit board would help when connecting the leads from a decoder. I understand that it is easy to solder a wire to copper clad circuit board, but all I can see is that the circuit board will take up more room and be harder to insulate. I have used circuit board lots of times but mostly for making mounting plates for power pick up on wheels.

Dave

  • Member since
    February, 2002
  • From: Reading, PA
  • 22,657 posts
Posted by rrinker on Monday, September 11, 2017 6:35 AM

 I've never liked that whole "lay the wires next to each other and solder" thing, which they seem to do a lot of in MR videos. On low power things like decoders I suppose it doesn't make much meaningful difference but a good mechanical joint makes for a better electrical joint than just filling the space and freezing both wires in solder.

 There definitely are at least 2 kinds of heat shrink. The shiny type is indeed hard and inflexible. Works best in the larger sizes for large wires. The small diameter stuff I use for decoders is a dull rubbery color and very flexible.

 And this is where a true variable temperature soldering station comes in handy (need not be expensive -mine was $50). Turned all the way down to the coolest setting, it shrinks the heat shrink without melting it and making a mess of the soldering iron. A heat gun is just way too big for small heat shrink in the confined space of a loco, at least in HO ir smaller. Maybe for large scale use it would be ok. A hot air soldering station (used for surface mount soldering) with the heat turned down would also work, they have small pinpoint air nozzles, but these are more expensive than a basic soldering station with a traditional iron.

 There's more wire there piled up behind the decoder than it looks from the top down view - however not so much that I needed to use another piece of kapton tape to keep it in place. Keep the wires short and neat - but not SO short you can't work.

                                    --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    December, 2015
  • 1,907 posts
Posted by BigDaddy on Monday, September 11, 2017 9:46 AM

Thanks for the suggestions.  I have the soldering station Randy suggested a year or two ago.  I bought a pack of colored wire from one of the DCC retailers, I don't see it on a website now, but that stuff is tiny  32 ga I think. 

It was easy to wrap it around the heavier gauge wire in an Atlas that I did, but wrapping the Atlas wire to complete the Western Union splice ended up just pulling the smaller wire off the larger.  Maybe I was too stingy with the amount of stripped wire.

Those are certainly neat installations.  Randy you had mentioned about running long end of the cabs forward.  I want to run the short end forward.  There is only one wire and a separate contact stip on the motor.  Do you remember how you wired yours?

My idea for the circuit board was to cut off a little piece of 6 holes and solder to it and then tape it to a piece of styrene.  The Loksound decoder is not wrapped in heat shrink like the TCS board, so I was going to tape the decoder to it as well.  I don't think I should be reinventing the wheel on this though.  I go with what is known to work.

 

Henry

COB Potomac & Northern

By the Chesapeake Bay

  • Member since
    February, 2002
  • From: Reading, PA
  • 22,657 posts
Posted by rrinker on Monday, September 11, 2017 12:39 PM

Mine are wired backwards because Life Like built them backwards. If you match colors it will run short hood forward. On mine, both motor contacts come out as wires. 

Actually zooming on on my picture, I wonder if I just reversed that one with CV29, because I have the orange decoder wire connected to the orange/red motor wire (goes to the bottom brush) and the grey decoder wire to the grey/black motor wire which goes to the top. I'd have to dig out the locoa nd look. I am SURE it ran the wrong way on DC - it's a first gen in as-built paint scheme, probably 90% of which ran long hood forward, and it has the F decal on the long hood end. Plus it's a model of the prototype that I model and I KNOW they ran the GP7's long hood forward. I am also pretty sure I tested them before soldering the wires to make sure I had it going the right way WITHOUT changing CV29. 

 That's the only thing I can suggest - before soldering the motor wires, test it. If it goes the right way, solder away, otherwise flip the motor leads. Just don;t let them touch each other or the metal chassis. Worst case, you can change NDOT in CV29, but I prefer to wire them up so no change to the NDOT setting is needed.

                                    --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    December, 2015
  • 1,907 posts
Posted by BigDaddy on Monday, September 11, 2017 5:48 PM

My freelance RR likes to be different, it suits my personality. 

My circuit board is connected both to the weight and the brass/copper strip at the top of the motor with only one orange wire coming from the bottom.  I will get try to test it before soldering

Decided I might as well replace the wires that come from the trucks to clean up the appearance.  Small gauge stranded wire is unobtainable locally.  The best I could come up with is 24 ga speaker wire, which is way better than 28 ga solid wire.

 

 

Henry

COB Potomac & Northern

By the Chesapeake Bay

  • Member since
    February, 2002
  • From: Reading, PA
  • 22,657 posts
Posted by rrinker on Monday, September 11, 2017 7:36 PM

 You can order decoder wire from Modeltrainstuff, or pretty much any of the online hobby shops. I'd use the right stuff, #24 is too big.

                               --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    December, 2015
  • 1,907 posts
Posted by BigDaddy on Monday, September 11, 2017 8:25 PM

rrinker

 You can order decoder wire from Modeltrainstuff, or pretty much any of the online hobby shops. I'd use the right stuff, #24 is too big.  --Randy

I was referring to replacing the wire that comes off the truck wires.  I have decoder wire, if you think that is not too small, I can use that.  My mindset was of thinking of wire gauge and DCC and thinking that too small a gauge wouldn't conduct adequate power

 
 

Henry

COB Potomac & Northern

By the Chesapeake Bay

  • Member since
    February, 2002
  • From: Reading, PA
  • 22,657 posts
Posted by rrinker on Tuesday, September 12, 2017 6:30 AM

 The decoder wire is fine for the truck power as well. It is, literally, the same stuff that is on decoder harnesses - unlike the bus wire, it only has to deal with the power of a single loco, and the lengths are only a few inches, so any voltage drop is pretty much immeasurable. The bus needs to be bigger because you cna have your entire loco fleet at the far end of many feet of wire. 5 amps of current dozens of feet away results in a much larger voltage drop if the wire is too small. A single loco is less than .5 amps, that's 1/10 the loss right there. And the wire in the loco, compared to a 20 foot bus, is more than 100 times shorter - that's 100 times less loss - so far 1000x less voltage drop, so even if the smaller wire has 50x greater resistance per foot than the large bus wire, we're AHEAD with 20x less loss - and the bus wire is sized for a .5 volt drop or less, so with the decoder wire in the loco, we're at .025 volt loss. The pickups rubbing on the wheels probbaly cause more drop, not to mentioon the first thing the track power hits inside the decoder circuit is a full wave rectifier, causing 1.4 volts to be lost due to the diode drops.

 So - decoder wire to run new truck pickup wires is so insignificant as to not be a problem. If you REALLY want to get fancy, there is wire that small that has a lot more strands, that wire is even more flexible. It's also more expensive and, for the amount of movement there shoould be under normal operatioon, not at all necessary.

                               --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    February, 2002
  • From: Mpls/St.Paul
  • 10,006 posts
Posted by wjstix on Tuesday, September 12, 2017 8:00 AM

Just to be sure...you know you don't have to "cut off" the 8-pin connector, it connects to the decoder with a 9-pin connection. You can just remove the harness - carefully pull it out - and replace it with one that has the 9-pin connection at one end and just wires on the other.

Stix
  • Member since
    December, 2015
  • 1,907 posts
Posted by BigDaddy on Tuesday, September 12, 2017 8:30 AM

wjstix
Just to be sure...you know you don't have to "cut off" the 8-pin connector, it connects to the decoder with a 9-pin connection. You can just remove the harness - carefully pull it out - and replace it with one that has the 9-pin connection at one end and just wires on the other.

I knew it!  Electricity is witchcraft.  As soon as I learn to wiggle my nose like Elizabeth Montgomery, I'll plug it into this board

 

Henry

COB Potomac & Northern

By the Chesapeake Bay

  • Member since
    February, 2002
  • From: Reading, PA
  • 22,657 posts
Posted by rrinker on Tuesday, September 12, 2017 12:47 PM

 Your GP7 must be an older run than any of my 4, mine have a much lager board with the diodes on. All wires - both truck pickups, both motor wires, front and rear light plus the common wire for them And 8 pins - MALE pins, so no, a decoder DOESN'T just plug in, except for the Digitrax DH163/165L0 and one that NCE had for a while and there was a Soundtraxx LC series I think that was a direct plug in. The decoder harnesses are almost always 9 pin to an 8 pin MALE, which means, no go here. Since yours doesn't even have that board, there's no plug in option.

                                --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    December, 2015
  • 1,907 posts
Posted by BigDaddy on Tuesday, September 12, 2017 2:17 PM

edit There is no price tag on the A unit, the B unit was $33.95

 I've got my threads and locos confused,  but the following is correct.
 
There is a trace on the board that says cut here for DCC.  I do not remember DCC from the 90's, I probably looked at as another version of command control to be replaced by the next greatest thing.
 
 
 
 

Henry

COB Potomac & Northern

By the Chesapeake Bay

  • Member since
    February, 2002
  • From: Reading, PA
  • 22,657 posts
Posted by rrinker on Tuesday, September 12, 2017 7:16 PM

A and B? Is it an F7, not a GP-7? Though I thought P2K F units came later. Maybe an FA?

                                      --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    December, 2015
  • 1,907 posts
Posted by BigDaddy on Tuesday, September 12, 2017 7:38 PM

I am working on 2 locos and threads at once (probably a bad idea) and got confused.

This is a GP9 not a 7 and was a recent Ebay purchase.  It says so on the board.

My Stewart F3's, different thread, have a larger circuit board, much like the Atlas DC circuit boards from long time ago. 

 

 

Henry

COB Potomac & Northern

By the Chesapeake Bay

  • Member since
    November, 2016
  • 118 posts
Posted by Lonnie Utah on Wednesday, September 13, 2017 1:59 PM

rrinker
 There definitely are at least 2 kinds of heat shrink. The shiny type is indeed hard and inflexible. Works best in the larger sizes for large wires. The small diameter stuff I use for decoders is a dull rubbery color and very flexible.

I'm fortunate enough to have an electronics supplier here that has colored shrink wrap in a multitude of colors and sizes. Usually when I do a decoder install, I try to remove all the existing wires and use wires and shrink wrap that corresponds to the nmra decoder wire color. 

 

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!
Popular on ModelRailroader.com
Model Railroader Newsletter See all
Sign up for our FREE e-newsletter and get model railroad news in your inbox!
ADVERTISEMENT
ADVERTISEMENT

Search the Community

Users Online

There are no community member online
ADVERTISEMENT
Find us on Facebook