Insulating Wire-to-Resistor Joints?

[tehachapifan]

What do folks use to insulate wire ends soldered to, say, a resistor? I find shrink tubing is typically a bit too large for N scale decoder-installation applications and I often solder resistors at a 90 degree angle to the wires anyway (the only way they fit in some of my applications), necessitating something that will tolerate that kind of bend. I believe I remember someone posting that they apply a few coats of ACC to the joint but wonder how well this works or if there are other solutions.

[railnerd]

Kapton tape is your (expensive) friend…

[jdcolombo]

Slip a piece of 1mm heat shrink tubing over wire, long enough to insulate joint and stretch to resistor body.  Solder wire to resistor with resistor straight.  Slip tubing over joint all the way to the resistor body.  Shrink tubing, making sure it stays in place next to resistor body.  1mm tubing will shrink very tight around joint and should not slip after shrink.  If you need a 90-degree angle, bend with needle-nose pliers AFTER shrinking tubing.  The tubing will bend. Done.

Here is a tubing possibility:

https://www.amazon.com/uxcell%C2%AE-Black-1mm-Dia-Shrink/dp/B00843KJYC

Or

http://www.digikey.com/product-detail/en/te-connectivity-raychem-cable-protection/MT2000-1.0-X-SP/MT2000-1.0-X-SP-01-ND/4155747

Digikey also has a bunch of 3/64" tubing that probably would work, too. 

John C.

[tehachapifan]

Kapton tape is your (expensive) friend…

This is what I have been using up till now in tight installations, however I recently found that the tape had started to release in one of my earlier installs (probably because I had to trim the sandwiched pieces of taps so close due to space constraints). Looking for something a little more reliable in this application.

Slip a piece of 1mm heat shrink tubing over wire, long enough to insulate joint and stretch to resistor body.  Solder wire to resistor with resistor straight.  Slip tubing over joint all the way to the resistor body.  Shrink tubing, making sure it stays in place next to resistor body.  1mm tubing will shrink very tight around joint and should not slip after shrink.  If you need a 90-degree angle, bend with needle-nose pliers AFTER shrinking tubing.  The tubing will bend. Done.

John C.

Thanks, John! This is the technique I've used on applications where there is a little more space available and the wire and resistor are more in-line, although I may not have been using the smallest diameter tubing available. Part of my challenge with the post bending technique you describe is that I often find I have to solder everything in position to minimize extra wire, etc. For example, I could post-bend the tubing like you describe on one side of the resistor but then I would not be able to do this on the other side without ending up with extra wire or creating the need for another solder joint elsewhere....unless I'm missing something (always possible!).

[Philip H]

Unless I missed something that heat shrink is not exactly cheap either. is the Unit price per piece or pack?

[jdcolombo]

The digikey tubing I linked is for a 12" piece, I think.  The tubing from Amazon is for 1 meter.  Tiny tubing is somewhat hard to find.  3/64" works, though, and is easier to find.

John C.

[Missaberoad]

Unless I missed something that heat shrink is not exactly cheap either. is the Unit price per piece or pack?

Digikey price is for 12 inches, Amazon price is for a meter (39.37 inches).


edit: Oops @jdcolombo beat me to it

[jdcolombo]

This is what I have been using up till now in tight installations, however I recently found that the tape had started to release in one of my earlier installs. Looking for something a little more reliable.

Thanks, John! This is the technique I've used on applications where there is a little more space available and the wire and resistor are more in-line, although I may not have been using the smallest diameter tubing available. Part of my challenge with the post bending technique you describe is that I often find I have to solder everything in position to minimize extra wire, etc. For example, I could post-bend the tubing like you describe on one side of the resistor but then I would not be able to do this on the other side without ending up with extra wire or creating the need for another solder joint elsewhere....unless I'm missing something (always possible!).

Hmmm.   Guess I can't picture why post-bending would create that much extra wire, unless you're using long resistor leads.  I usually don't have a resistor lead that's more than 1/4" and if you bend that post-soldering, you don't end up with much extra wire.  Have you thought about using SMT resistors?

Another possibility, though I haven't done this, is to get some liquid electrical tape, and brush that on after you've soldered and bended.  I've used liquid tape in household applications and it works well.

John

[tehachapifan]

Hmmm.   Guess I can't picture why post-bending would create that much extra wire, unless you're using long resistor leads.  I usually don't have a resistor lead that's more than 1/4" and if you bend that post-soldering, you don't end up with much extra wire.  Have you thought about using SMT resistors?

Another possibility, though I haven't done this, is to get some liquid electrical tape, and brush that on after you've soldered and bended.  I've used liquid tape in household applications and it works well.

John

I probably wouldn't end up with a lot of extra wire, just enough to create a little loop or bend I would have to find a way to tuck with all the other wires (and their loops and bends) when finished. Keep in mind, I model the SP with all its lights (some are small switcher models). So, I typically have anywhere from 3 to 6 SMD LED's with resistors I have squeeze into the model somewhere along with all the wires. For LED's that are installed on the drive itself (not so much with LED's mounted in the shell that need extra wire anyway), the more I can keep wires in a straight run without extra loops or bends, the better chance of pulling off getting it all tucked away when done. I often find that, in many of my installs, that I usually have the most room for resistors is at the opposite end of the drive from the decoder. So, I will usually have wires run to the other end to the resistors, then back for any LED's mounted on the end with the decoder. This can end up being a lot of wires to have to deal with!

All this said, the liquid electrical tape sounds like a possibility. Might have to give that a try.

[bobthebear]

Liquid electrical tape works fine. If it's good enough for the automotive industry................

[peteski]

Resistors with leads are so 20th Century!     All kidding aside, I have been almost exclusively using SMD (Surface Mount Devices) resistors for many years now.  They are a lot smaller and there are no leads to take up space.

You can solder small gauge wires directly to the tinned terminals then use some thin-wall small-diameter heat-shrink tubing to neatly encapsulate the assembly.  Yes, there is a such thing as thin-wall tubing as opposed to regular thickness or extra heavy tubing. Digikey is where I get mine. It does seem pricey but if you consider how long few feet of the stuff will last you, it is not that bad.

Then you can take this to the next level and etch your own circuit boards to house the resistors and wiring. Then (since the bottom of the board is an insulator) there is no need to insulate the entire assembly. Just stick it to the frame or shell.  It is really easy to do simple etchings like those.



I thoroughly clean the copper cladding on a blank piece of PC Board, then draw the masks for the traces using an old technical pen (or whatever those are called) using some thinned Testors paint. Next I immerse it in small amount of Ferric Chloride etchant and 20 minutes later I have a circuit board!
E77Hdlights_01.jpg


PhotoetchingTools02.JPG

[tehachapifan]

Great stuff, Peteski! I remember seeing that before and would certainly like to give that a try at some point. That said, in some of my applications I'm not exactly sure how I would integrate your approach. I often use a hardwire decoder with a bundle of wires already coming out of one end. It seems that the easiest approach is to solder a resistor to each of the existing function wires and then extend the LED leads from there. Trying to figure out where and how a PC board would tie into all that seems to add another level of complexity.

[jeffstri]

Gallery Glass should work well for this. Out of the bottle it's a bit thicker than white glue, and when dry it's rubbery and tougher than liquid electrical tape, and it insulates well. 

It comes in a variety of colors.  Crystal clear Gallery Glass is great for encapsulating and attaching wired smd LEDs to headlight or other lenses, as well as making lenses for ditch lights, etc. I've also used it to attach smd LEDs and resistors to metal locomotive frames.

https://www.amazon.com/Plaid-Gallery-Glass-Window-crystal/dp/B007T7POGM

[tehachapifan]

Thanks, Jeffstri! I actually tried some Micro Krystal Klear in the same fashion but found it did not seem durable enough, breaking off of one of the joints that I tried it on (it's kind of rubbery when dry too).

[peteski]

Great stuff, Peteski! I remember seeing that before and would certainly like to give that a try at some point. That said, in some of my applications I'm not exactly sure how I would integrate your approach. I often use a hardwire decoder with a bundle of wires already coming out of one end. It seems that the easiest approach is to solder a resistor to each of the existing function wires and then extend the LED leads from there. Trying to figure out where and how a PC board would tie into all that seems to add another level of complexity.

Most of my installs are also hardwired decoders, but I often take the wrapper of the decoder and replace the factory wires with my own wire harness. I often find the factory-installed wires too stiff or too thick.

Yes, PC boards are taking it to the next level. I find it nice to have a convenient mounting place for a small LED and/or a resistor.  The alternative is, like I mentioned, just use the SMD resistors instead of the leaded resistors and then insulate the assembly with one of the insulating methods mentioned in this thread. Those take up less space and they fit better in tight quarters.