This post is really a part of my continuing build log article on the Repair Shop, but I thought it might be of general interest. This is how I install lighting by making my own LED fixtures. The interior of the repair bay is illuminated with fifteen light fixtures, arranged in five rows of three fixtures. Each row is directly under one of the main roof trusses.

I started casting the fixture shades in acrylic resin using a silicone rubber mold last night. I will post more photos when the shades are completed. If you do not want to cast your own fixtures, a suitable substitution would be the metal casting from an Ozark Miniatures drop light kit, OM P/N 264. Each fixture will hold a single 3mm warm white 60-degree viewing angle LED. The LEDs are available from The LED Light Company, http://www.theledlight.com/, item number LED3-60DG-WWY-6.

I made the receptacles from a single 30-pin IC strip socket by cutting the socket into fifteen pieces with two pins on each piece. The strip socket is available from Jameco Electronics, http://www.jameco.com/, P/N 104054.

I bent the pins on each receptacle at a 90 degree angle away from each other. I cut pieces of 3/64” diameter brass tubing to connect the receptacles. The brass tubing has an inside diameter of 0.035 inches which makes for a nice tight fit with the 0.025” square pins on the receptacles. The 3/64” outside diameter accurately represents 1” diameter metal conduit in 1:20.3 scale. I placed miniature brass eye pins on each section of brass tubing before inserting the receptacle pins into the tubing. The eye pins are available from Micro-Mark, http://www.micromark.com/, item number 60405. The loops of the eye pins are 3/64” inside diameter so they fit tightly over the brass tubing. I clipped off the pointed end of the eye pins about ¼” above the loop. Here are the parts needed for each truss.

I flowed a small amount of solder into the ends of the brass tubes where the receptacle pins were inserted to guarantee good electrical contact between the pins and the tubing. I soldered a 2” length of brass wire into the left end of the tubing. I soldered one lead of a 120 ohm, ¼ W resistor into the right end of the tubing. I drilled small holes in the underside of the truss for the eye pins and attached assembled section to the truss. I painted the plastic portion of the receptacles and the soldered brass leads with flat black acrylic paint. Here is how the assembled conduit and receptacles fit on the undersides of the trusses.

Here is a close-up of one of the receptacles.

When the trusses are added to the structure, I will solder the end of the brass wire connected to the left ends of the tubing to the +12 volt lighting bus which runs along the top of the large center support beam. I will solder the end of the resistor connected to the right end of the tubing to the ground bus which runs along the top of the right wall.

The fifteen LEDs will be wired in a 3 x 5 series/parallel array. Each 120 ohm resistor dissipates 48 mW. Together, all resistors dissipate 240 mW. Together, the 15 LEDs dissipate 960 mW. Total power dissipated by the array is 1200 mW. The array draws 100 mA of current from the +12 volt lighting power bus.

This lighting arrangement provides excellent illumination for the interior of the repair bay. The warm color enhances the wood surfaces and brings out the interior detail. The 60 degree dispersion angle spreads the light evenly. The “plug-in” fixtures allow for convenient replacement if a LED ever burns out. The 100 mA current draw is extremely low for the amount of light produced. The required parts were readily available, easy to assemble, and relatively inexpensive.

Bob

That is interesting! Great idea…

Looks great, cant wait to see it completed.

That’s pretty neat, and I love the idea of brass tubing as “wiring”.

That’s cool. Looks like conduit.

Excellent

Very nice Bob. Excellent idea on the “conduit”.

UPDATE: Here is the silicone rubber mold I made to cast the fixtures. I used old Lego blocks to build the mold box. At the bottom are a couple of reject castings from the first pour before I cut better air vents.

I cut short 1/4" pieces of heat shrink and put them on the leads - white on positive and black on negative. This is to keep the polarity straight after I clip the leads to final length. I used a heat gun to shrink the tubing in place.

I drilled a 1/8" hole through the neck of the fixtures. I painted the inside with gloss white and the outside with satin forest green. I put a dab of silicone caulk on the heat shrink and inserted the LEDs into the fixtures. Here is how they turned out.

Tomorrow, after the silicone caulk sets up, I will clip the leads about 1/8" above the top of the fixtures and insert them into the receptacles. I’ll post some final photos after the trusses are mounted on the structure.

Bob

Oh that is such a cool application of modern electronics technology for model railroading. My only question… why not just cast the led into the shade?

Bob, cool. So when do you start full scale production? and what is the street price for them?

Great job!
One could use the plastic found inside a large tube of toothpaste, instead of casting your own.
In this case it might take some time and a lot of teeth brushing to get 15 of them

Fantastic idea and work. Thanks for sharing.