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Adding Lights to a BLI Trackmobile

Recently, a friend from the PSMRRC club asked me if I wanted to add some lights to his BLI Trackmobile. I enjoy doing unusual installations (relative to the standard locomotive headlight/ditchlight install) so I took him up on the project. Granted, this wasn’t as much a departure from the norm as some of my other builds, but I thought it might be interesting to do a short photo documentation to show the process. I also just wanted to test out a new macro lens – I apologize in advance as some of the shots might not be as clear as they should be. Now, without further ado, let’s begin!

First I disassembled the model. It is very well made and comes apart easily. Everything is screwed on and has locating pins to keep the number of screws low. After everything was apart, I drilled holes for the LED wires. The plan was to have two amber strobes on the roof, and 4 white lights – two up front and two in the back.

There are certainly more lights on the prototype, but if you look at videos on youtube, the 6 lights I was installing were the prominent ones. I think sometimes we fall victim to the notion that we should be reproducing all of the details we see on the real thing, and in the end, the model starts resembling a christmas tree and the overall “feel” that we are trying to emulate is lost.

When soldering LEDs, I like to test them to make sure they actually work, and to refresh my memory as to which side is positive and negative. Every now and then I have gotten a defective LED from Chinese sellers, but the price per LED is still worth it in my opinion. 

My testing setup is pretty simple. I reconfigured a set of tweezers (read: sawed in half) and attached leads with banana plugs on the ends. I made sure both sides of the stainless steel tweezers were isolated, and added a piece of black heat shrink tubing to help me identify which side was negative. Then I plugged them into my trusty Lambda power supply – I highly recommend one, and they can be picked up for cheap on ebay or in surplus stores. It’s important to keep in mind the forward voltage of the LEDs when testing them (or you can also run the power supply in current limiting mode)

Soldering the enameled wire to the LED can be tricky at first, but with practice it isn’t difficult to get good results. I might have used a tad too much rosin flux on this one, but it’s a good joint nevertheless. If I don’t have my go-to setup of a “third hand” clamp with self locking tweezers, I use blue tape to stick hold the led in place while I solder the leads to the chip. 

A quick test reveals that the leads are properly attached and the LED lights up. Then I installed them on the roof of the trackmobile with a dab of CA, making sure the exposed leads weren’t shorting out on the bare metal body of the roof. The loose wires were routed along the outside of the window glass and secured it with more CA. This strain relief is important when the model is being assembled and disassembled for maintenance.

The white headlights proved to be a bit more of a task to install. They were just a fraction of a millimeter too long, so the tabs had to be carefully filed down for the LED to fit into its recess. There is no good way of doing this – I held the LED down on the blue tape with my fingernail and carefully brushed it with a miniature file. Going too far would sever the connection between the top and bottom of the pad and render the LED useless.

Having finished all 4 LEDs, I breathed a sigh of relief and went back to the easy (sort of) part of installing them in the frame.

After installing them, I tested the lights one more time – it’s easy to break the soldering joints, or the magnet wire when installing them into tight spaces. 

All finished, looking promising if I may say so myself. Each of the lead wires was glued to the frame next to where the LED was mounted to keep them from breaking.

Every LED needs a resistor to limit the current it can draw from the decoder. I like to make “resistor boards” to keep all of the components in a single, central location. This makes it a lot easier to troubleshoot any issues that may crop up, and keeps a lot of small components attached to a sturdy PCB. I like to use the scraps from the PC ties I use for my handlaid track. I used two large 2.2K resistors for the amber LEDs and four 1K resistors for the white lights. 

Making the PC board is fairly simple – I use a dremel with a ceramic cutoff wheel to cut slots to isolate the resistors from each other. One side is a continuous strip, where I will later solder on the blue common positive wire from the decoder. The other side is where I solder the leads for the LEDs.

First I tin the pads with solder, then add in the resistors between the two sides and make sure the solder bridges the gap. Notice how tiny the 1K resistors are – If I were to do this again, I would probably use one size larger, just for the ease of soldering.

Next I installed the resistor board to the underside of the trackmobile frame, and wired in all of the positive leads from the LEDs. Once again, CA was used to fix the wires in place in certain locations.

With that, the LED work was nearly finished and it was time to work on the decoder replacement. The stock model didn’t have any lighting options (I stand corrected, apparently there are a few pads for headlights, but not strobes), so I had to replace it with a Digitrax DZ143. The installation was a direct drop in.

I reassembled the vehicle, routing the lighting wires outside the lower chassis and to the underside of the frame. Then I soldered the connections – headlights to one wire, rear lights to another, and the strobes to their own separate wires. I coated the bare soldering joints with some nail polish – that stuff works very well to insulate the joints and dries quickly. Plus, it’s cheaper than liquid electrical tape.

With everything assembled, I programmed the decoder using JMRI Decoder Pro 3 and set the two amber LEDs on the roof to be alternating single strobes. They can be toggled on and off using function 1. With that ended my lighting installation, and I enjoyed running the little guy on my test track. I’m pretty happy with the installation and I think the lighting effects make it a more dynamic model.

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