Working with magnet wire in signal installations

[GaryHinshaw]

I'm starting to plan my signal installation on Tehachapi BC and I'm looking for tips on the mechanical aspects of the installation.  I'm using RRCirKits Signalman boards and Showcase Miniatures searchlight signals.  For lighting, RRCirKits has some nice 3-color LEDs that are pre-wired with four 36 ga magnet wire leads, so each signal will have 4 or 8 leads (1 or 2 signal heads) to terminate at the board.  The leads are 24" long, but in many cases the board will be more than 24" from the signals it controls, so I'll need some intermediate run of wire to connect the signals to the boards.

I'm looking for general advice on how to terminate the fine wire and connect it to the electronics.  I'm open to all ideas, from plugs in the base of the signal to direct connections to the board.   The boards themselves have 3 connector options: compression connectors, pin connectors, and screw terminals.  They also have a break-out board which converts from pin connectors to screw terminals.  Before I buy a full lot of boards, I need to settle the connector question.

I have a test installation with one board and signal and I have verified that these screw terminals accept 36 ga wire just fine, so I have one approach available, but I'm looking for better ideas (and product suggestions) for connecting 36 ga wire to the "outside world" and I'm sure this group has some good suggestions. 

Thanks,
Gary

[RBrodzinsky]

I have found that the only long term reliable method for connecting/extending magnet wire is soldering. I use small PCB boards, or PCB ties, and attach the leads accordingly. This also lets me gap the board and add SMD resistors, and to gang the common wires of the install.  After the board, use either fine solid or stranded insulated wires for the rest of your run.

[bbussey]

Ditto. With my dwarf signals, I soldered the magnet wire to small PCBs and then soldered larger gauge wire to the board as well tobrun to the power.

[C855B]

Of the zillions of projects I have in the queue, designing and executing a plug base system in Shapeways is one of them. I have knocked over the one working "test" signal bridge countless times since it's in the middle of my work area on the layout, thankful each time that the wires are dangling off the heads and not affixed to the bridge yet. It's a BLMA bridge just pressed into the foam at the moment. IOW, I feel it is important to have something that yields to misdirected fingers and elbows, and the corollary, ease of replacement.

The plan is to use 2-row 1mm/.050" header strips cut to size, press-fit into the holder bits. I'll need 12 leads in some cases for masts with three heads, so the base will have to accommodate a 2x6 mm plug and socket. Theoretically I might need 24 for each side of a double-track signal bridge if populated fore and aft with three-headed masts, although I'm not recalling having anything that intense on the plan.

Between the receiver and the logic board are #28. I've been using scrap decoder wire in the tests, but have real reels of this size on-hand. #24 would be a push with 1mm headers.

Alvin @Wutter produced PC-board bases a while back to fit the Showcase masts, similar to what Bryan did but for 8 leads. I have 10 on the bench at the studio, so I'll snap a pic when we get over there later today.

[peteski]

Actially the PV Board Bryan used for that dwarf signal looks like a board I etched for him (for another project).  He seems to have re-purposed it for the signal base.

I agree that best  (and easiest IMO) way to transition from magnet wire to  a more substantial standard insulated wire is by using a PC board.  While custom made etched board is the best, a one which has the copper cladding pads made by scoring or grinding the copper away will also work.

There are many  sources for PC board material.  I usually get mine from surplus electronic dealers like All Electronics or Electronic Goldmne.

The PC board itself can then be easily attached (gluesd or screwed) just abuyt anywhere.  And its size can be anything you want or feel comfortable dealing with.

Stripping insulation from magnet wire is a breeze if one has an adjustable temp. soldering iron. Just crank the tip temperature to about 800-85 degrees, put a ball of solder on the tip and stick the end of the magnet wire in the solder. That strips the insulation, and tins the wire, all in one operation. I usually dip the end of the wire in paste flux before stripping for a clean stripping/tinning.

[Lemosteam]

Why not use PC ties for this?  Cut as many grooves as you need for the number pf pads you need, tin the tie pads, lay both wires on the each pad in opposite directions and solder the wires to the tie in one touch. add a short section of 3/4" shrink wrap for protection and done.  use the excess shrink wrap to screw the assembly to the benchwork.

[DKS]

I'm of the mind that signals are best made removable from a layout, especially those that span the track--just the act of cleaning track can put signals (and similar items) at risk. To that end, I've made my signals unpluggable. I attach the signal mast to a piece of PC board that I've made into a plug using brass wire for pins, which are spaced to match sockets in micro-connectors I've scrounged from old VCRs and other tech. I embed the socket permanently in the scenery, which leaves only sturdy stranded wire on the underside of the layout to connect to the electronics.

PC board plug:



Socket:



Mast attached to PC board plug:



Plugged in:



Some weeds hide the plug:

[bbussey]

Actially the PV Board Bryan used for that dwarf signal looks like a board I etched for him (for another project).  He seems to have re-purposed it for the signal base...

Nope, I designed and etched them myself, but I followed your recommendations regarding the materials and design.

[GaryHinshaw]

Thanks for the great feedback guys, lots of good food for thought.  I really like the idea of pluggable (though not really necessary for dwarf signals like Bryan's nice setup.  David's example is exactly the kind of installation I was imagining for mast signals, but I've also toyed with the idea of magnets and enough slack on the leads that they would easily yield when knocked by a stray arm or piece rolling stock.

For sockets, I don't especially relish the idea of scrounging 40 or so surplus connectors from VCRs... Anyone have a recommended source for sockets like this?

Mike, I'd love to see a photo of Alex's board if you get a chance.

-gfh

[C855B]

@Wutter 's signal base, bottom and top. Notice the pads for resistors. My 1mm/.050" two-row male and female connector strips are in the back:



EDIT: Here's a 1-row version of a connector pair used for a shell disconnect:

[Wutter]

This is what the signals look like after they are built on top of the PCB I have. I actually have two versions of the board now, one that allows for both 1.6mm (1/16th) and 0.8mm (1/32) tubing and one that is only the smaller size. My signals as well as Showcase use the more accurate size of 0.8mm. Press fit frames shown are printed from Shapeways FDM.



Like Mike showed, the bottom of the board allows for ten 0603 resistor locations and allows for the transfer from magnet wire to 22 gauge wire.

I take one of these 4 position cables and solder one of the ends in and use the plug end to drive the signals.
 

[peteski]

Nope, I designed and etched them myself, but I followed your recommendations regarding the materials and design.

On a second look, it is a bit different (but looks quit similar).   

[peteski]

For sockets, I don't especially relish the idea of scrounging 40 or so surplus connectors from VCRs... Anyone have a recommended source for sockets like this?

Mike, I'd love to see a photo of Alex's board if you get a chance.

-gfh

Digikey and Mouser have more flavors and sizes of connectors than you can shake a stick at. They actually have so many that the selection is mind-boggling.  Then there is eBay.   You'll have to figure out exactly what you want to narrow tour search for a connector ideal for your needs.  If you want the crimp-type terminals on the insulated-wire side you will likely need ot buy a crimping tool for fast and reliable assembly.

Why not use PC ties for this? 

Sure, it is a strip of fiberglass/epoxy PC Board after all. Perfectly reasonable solution.

[GaryHinshaw]

Those base boards look great Alvin (@Wutter).  Are they still available for purchase?

Thanks again to all for the feedback.

[GaryHinshaw]

A quick follow-up for you Mike (@C855B): are you planning to use the plug stock as a mechanical connector, or just the termination of a short pigtail from the base?   I gather Alvin's 2-part base is intended to provide adequate mechanical support on its own.

-gfh