Conductive Paint

[Guest Closed Account 1]

Many of you know how sensitive modular track is to soldering. Easy to mess up.

 

I found a Conductive paint that has a thick viscosity to bond wires to plastic modular track.

 

Another version is used to replace low voltage wires. To hide them from sight. Inside buildings, cars, automobiles, etc. Use like copper tape.

 

Instead of soldering feeder wires to the Kato Unitram trolley track I will be using Solder5 from trainaids.com.  So far, initial test have revealed only 1 ohm resistance after drying overnight.

 

Below is my test piece on Unitrack with Solder5. I filled up the hole under the sleeper.

 

Easy to work with once thorough mixing is complete. Just dab a little on the rail and the exposed wire. Secure wire overnight. Do not disturb while drying.

[cteno4]

not sure how long the bond will hold, i think ardesh said it was pretty strong stuff, but i might worry it would end up breaking loose from the rail in the really long run. any voltage drop across the joint? also wonder what the amperage you can get through this stuff, its basically silver particles in glue.

 

ive found it really easy to just cut a slit below the rail with a small burr cutter in the roto tool the solder a lead to it. i pretin the wire and put a dab of flux on the rail, put the wire on top of the rail and the iron down touching the rail with the tip and the side on the pretined wire and it bonds super quick. i basically did all my ttrak modules with soldered leads like this so i could put leads where ever i wanted. i dremeled and soldered like 40 pieces of track in maybe 1.5 hrs. and a lot of that time was cutting wire, splitting, and stripping the wires.

 

i have a bottle of the liquid solder i have been meaning to try on some tiny, tiny smd leds i have, but i worry the heat in the long run might loosen the joint, so want to see how it will hold up in some tests.

 

cheers

 

jeff

[Guest Closed Account 1]

I barely put any heat on the Unitram rail and the thin plastic nearby was affected.  Not risking those plates $$$$.  I have to go other options like the cold solder.

 

My only other option is $5 Unitram feeder connectors and change the wire colors.

 

Using the colder solder products one can drop some CA over the solder when cured and then it'll never jiggle off.

[cteno4]

trick is to pretin and also have some flux on it. ive done flat unitrak and also the concrete plate rail in the double viaduct this way. thing would be to dremel out a bit of the plastic under the rail for like a half inch. ill ask ardesh next time i see him about the conductive paint, i remember him telling me what it was good for and not good for and its limitations.

 

jeff

[Guest Closed Account 1]

Expose the rail flush with the underside?

 

I did try the pretin and use flux. Even scuffed the underside of the rail and used a 1/8 tip.

 

What distorts are the thin keepers where the sleepers would be.

 

I have to put the feeders under the track, not at the joiners, for the automation blocks.

[cteno4]

hugh, thats pretty much what ive done with unitrak and viaduct unitrak with the cut slots. never opened up the bottom of the unitram to see the nice slots in there! wish they would do that on unitrak instead of just the tiny squares.

 

for this i use a chisel tip so i have a long flat tip surface on the track and a nice flat side surface on the pretinned wire. bonds fast w/o melting much at all. might try tinning the track and see if maybe the flux you are using just does not do well between the solder and the rail nickelsilver.

 

i guess you could conductive glue to the track in the middle of a slot here then fill in the slot all around the joint and track with a glob of epoxy after its set up.

 

do check for voltage drop though and i would also test a couple of sections with your block detection circuit to make sure that the conductive joint does not effect it.

 

cheers

 

jeff

[Guest Closed Account 1]

Jeff:

 

That's the underside of Unitram as is.

 

I'll try again tomorrow. Thanks.

[The_Ghan]

I've had similar problems soldering to Tomix track.  I've been practicing on a piece of S140 that I'm prepared to throw away.  I'm still melting bits of plastic.  Soldering to Peco is much easier.  I think I need a couple of heat sinks on the rail I'm soldering to.  I've tried a couple of small metal clamps, but to no avail.

 

I'd love to see a video of someone doing this right.

 

Skip, thanks for the heads-up on the Solder5.  I might just get me some!!!

 

Cheers

 

The_Ghan

[Guest Closed Account 1]

  I think I need a couple of heat sinks on the rail I'm soldering to.  I've tried a couple of small metal clamps, but to no avail.

 

Try multiple mini alligator clips or small binder clips? It's all metal. Anything to radiate heat. Even aluminum foil and alligator clips. Been there done that at an RC track.

[KenS]

not sure how long the bond will hold, i think ardesh said it was pretty strong stuff, but i might worry it would end up breaking loose from the rail in the really long run. any voltage drop across the joint? also wonder what the amperage you can get through this stuff, its basically silver particles in glue.

 

There are two basic formulations for conductive glue that I've found, silver-based (I found this in epoxy form) and carbon-based, which is usually made in a water-soluable form.  I don't have any experience with the epoxy, but I'm very impressed with the water-based carbon powder stuff.

 

I glued a wire to a strip of copper tape on a sheet of plastic using water-soluble "wire glue" (which appears to be a carbon-powder form; it dries overnight to a black solid) for a test in July.  It worked well, so I put it on my workbench on top of some junk and forgot about it. It got bumped, moved around, buried under other junk, and two months later the end of the copper tape had peeled up from the styrene, but the wire was still glued to the copper tape. In fact it's sitting on a shelf in the basement, where it's been for the last several months, and six months on a quick check shows the wire still so firmly attached to the copper tape that tugging gently on it doesn't separate them.

 

I can't say all conductive glues work the same. But this one seems quite durable. And if anything, I'd expect an epoxy to be better. One tip I've read for making them more durable, is to coat the wire glue (after it's fully dried) with a layer of superglue to seal it to the surrounding material. I didn't test that, as my main application is inside buildings, where super-glue is ruled out due to its fogging effect on windows. But that wouldn't be an issue in a track feeder.

 

As for resistance, I haven't used it except after making the two bits of metal touch, to surround and bond them, so I've never directly measured the resistance of the glue, just a metal-on-metal-with-glue bond.  In that approach, I couldn't measure the resistance of the joint (meaning it was under 0.1 ohms), and after running 1.2 amps at 12V through it for 5 minutes I detected no heating (using an IR thermometer).

 

It's not going to be as good as a soldered joint. And I can't say it will still be a solid joint ten years from now the way solder would. But for a track feeder that's not under any kind of mechanical stress, I think a glued joint would work pretty well.

 

Edit: I just noticed the original note said "conductive paint".  I've read one comment somewhere that conductive paint has a higher resistance, so that's a potential issue.

[Guest Closed Account 1]

***Health Hazard***

 

Do not apply heat to Superglue, aka CA or Cynoacrylate.

 

The Cyanide in the glue will separate and become airborne.

 

So that puff of smoke may be your last.

 

You can always remove epoxy from plastic, CA is forever.

[Martijn Meerts]

Skip, it doesn't instantly kill, but it smells pretty foul ;)

[Guest Closed Account 1]

Ken:

 

Which of the two conductives do you recommend?

 

Is it TrainAidsa?

[cteno4]

im pretty sure the trainaids is the silver with epoxy base. ill check with ardesh.

 

jeff

[KenS]

Which of the two conductives do you recommend?

 

Is it TrainAidsa?

 

The only one I've used is the "Wire Glue", which I got from Amazon:

 

http://www.amazon.com/American-Science-Surplus-WIRE-GLUE/dp/B000Z9H7ZW

[cteno4]

i talked to ardesh at trainaids yesterday, the conductive paint and the solder5 glue are basically the same stuff, its jus the solder5 is much more viscous and makes a better bond joint than the thinner paint will. its primarily nickel nanospheres with some silver to help the conductivity.

 

im going to try the solder5, i only had the other conductive paint. maybe the viscous stuff will work better for my tiny smd leds that are literally about the size of a grain of sand...

 

jeff

[inobu]

In one of my decoder installs I tried to use a "liquid" material to replace soldering and my findings is its not something you can rely on.

 

The products are some what a marketing gimmick.

 

There is a difference in electrical conductivity and electrical conduction.

 

We are keying on electrical conduction to operate a smooth railroad. The most efficient means to move electrically charged particles from one rail to another is the goal.

This flow is energy occurs at a molecular level. The reason that soldering is the most effective/efficient means is the metals are heated to a point that a molecular bond is created by way of the solder. This process supports the "conduction".

 

These liquid products are sold under the banner of conductivity. These products have electrical conductive properties but their "electrical conduction" is another story.

 

Solder bonds the metals at a molecular level where as these liquids only provide surface bonding. Surface bonding with conductive particles in the mix is not enough to support the conduction requirements we want/need.

 

I would continue to look for a better solution.

 

Inobu

 

I'm trying to think of one..............

 

 

 

 

[cteno4]

My concern as well for the power feeds as well as block detection.

 

Jeff

[CaptOblivious]

I've used a conductive glue in one install. Having eletrical reliability issues, as per Inobu's warning, although the bond is quite good.

 

I worry about the 1ohm number cited earlier in the dicsussion. While that might not sound like much, its WAY more than  an equivalent solder bond, and could be prone to heating up! A stalled motor...rare, but it could happen...drawing 1A across 1Ohm will generate 1W of heat, quite a lot for a little dab of paint to handle!

[Guest Closed Account 1]

So who has successfully soldered to unitram plates without melting plastic? How did you do it?

[cteno4]

ill try and open up a unitram plate to look at it, but i cant think its much different than the cutting the slot under untrak roadbed track or viaduct slab track. really no bad melting has occurred there for me. usually hard to just cut the slot straight in the plastic, ive always just used a burr bit, but a small saw blade might work better.

 

might think about just taking a burr bit and cutting the edge of the slots back at a 45 angle on one side to have room to get your iron tip in there. again i have a chisel tip for this and have the flat end of the tip down on the rail and the pretinned wire right next to that. only melting i get is if the other side of the tip hits the edge of the plastic slot i cut. with the jrm layout viaduct (we did like 9 viaduct double track power drops) and my ttrak ive probably done at least a hundred of these joints and no real melting issues at all. i dont use a heat sink on the rails. flux helps, but ive even done it with just pretinned wires with rosin core solder.

 

even if you melt the plastic unitram base a bit, isnt all that covered up by the roadway piece on top of it?

 

i think i have a few loose ttrak feeders in the basement somewhere ill see if i can find them and take some picts of them.

 

jeff

[KenS]

I've used a conductive glue in one install. Having eletrical reliability issues, as per Inobu's warning, although the bond is quite good.

 

I worry about the 1ohm number cited earlier in the dicsussion. While that might not sound like much, its WAY more than  an equivalent solder bond, and could be prone to heating up! A stalled motor...rare, but it could happen...drawing 1A across 1Ohm will generate 1W of heat, quite a lot for a little dab of paint to handle!

 

I wouldn't want to use conductive glue alone as a wire, but as a way to join two wires it does seem to work.  This may depend on the specific type of glue used and I haven't tested others. And it's going to depend on a good metal to metal attachment so the glue itself is doing a minimum of the conduction (i.e., as with wood to wood gluing, properly clamping the pieces to be glued is important).

 

But in my test, resistance was below what my meter could read reliably (around 0.1 ohms) and I detected negligible heating with 1.2 Amps over a five-minute period. I didn't test anything more, as my intended use is lighting and 1.2 Amps is close to my worst case (I'm using a 1.5Amp fused supply). But that's still more than you're going to get out of a typical N-scale power pack and much more than a modern train draws.  DCC is another matter, but even there one feeder shouldn't be feeding more than one train, which is a fraction of an amp unless you get a short.

 

Solder is definitely better. But if someone doesn't have the skill or confidence to solder in close proximity to something like a Unitram plate a good metal to metal bond held in place with conductive glue looks to me like it would provide an alternative.

[Guest Closed Account 1]

I did it!

 

Bought the widest tip for my soldering station. 4.8mm.

 

Granted I wish the screwdriver tips were longer so the heat won't melt the edges.

 

The rails are lying directly on a metal surface to sink the heat.

 

I was able to heat up the rail for 5 seconds and then set the tinned wire. Max 10 seconds total.

 

600 degrees tip temp. Applied flux with flux pen onto the track.

 

Ugly Soldering:

First pics show too much heat and what can happen if you hold the tip there too long. No heat sinking and...Cracked! Test car had plenty of clearance in the webbing. No warped rails due to the melted plastic holding the feet. Little bit of browning on the head. So glad the sacrificial track can be used. $$

 

Last pics still shows too much coffee. Concentrate and keep the tip on the rails and not touch the plastic.

 

Actually my first attempts were perfect, I just got overzealous and used the wrong color wire and had to redo the first piece of track.

 

Throughout the Tram automated scene Yellow will be the common. The other 3 colors ( Orange, Purple, Green, Blue) control power to the outer rails and make the wiring underneath look like sherbet. No mistake that this color combination will not be confused with the main tracks.

 

This method can be used for Unitrack. You must open the access to the rails with a drill bit or other so as to only heat the rails.

[cteno4]

Hey congrats! good job.

 

soldering like this is one of those things thats just like getting to carnegie hall, practice, practice, practice!

 

i was going to suggest you sacrifice a couple of hunks of regular unitrak to practice on but, by george, i think you have.

 

one think on your wire, once you strip it give it a few even twists (in the twist direction) between your finger tips to tighten up the wire braid twist nice and tight before pretinning. you will find the wire braid will hold together much better when you remelt it onto the track. helps to keep the wire from fraying.

 

now if you want to make sure it will stay there well you could put a dab of thick epoxy glue over it to lock it all in there so any wire stress does not go to the solder joint, but i think you will find its pretty tough. i yanked hard on a bunch of mine but could never bust one.

 

perseverance pays off! tally ho!

 

cheers

 

jeff

[inobu]

Skipper,

 

Glad you got it done but I'm going to push you to do better.

 

Here is the problem..too much heat. You have to balance everything. You need low temp solder. The thinner the strand the lower the melting point. This reduces the time you have to heat up the rail which reduces the chance of melting the plastic.

 

Your soldering process should be no more than 5 seconds total but you should have 3 steps.

 

1.  tin the wire.

2.  tin the rail.

3.  Solder the two together becasue they are tinned then it should require 3 seconds or so.

 

You should have a needle tip solder and thread thin solder. [smg id=806]

 

 

The idea is the iron tip heats the metal area, you dab the solder right in front of the tip. The metal melts the solder and it flows into the pores of the metal. When it cools the solders bonds.  

 

This image shows the solder in the traces similar to the rail. Soldering is a breeze now as the tip can melt the solder fast and you just have introduce a tinned wire and you are done. 5 seconds at the max.

 

[smg id=986]

 

As Jeff stated practice but remember you are heating the rail and dabbing the solder to the rail not putting the solder on the tip and globbing the solder to hold the wire.  

 

Inobu