Traffic Lights Part I - Light Standards

By Ty’s Model Railroad - 7/07/2012 06:20:00 PM

Six completed and illuminated scratch built traffic lights with metallic silver painted light standard

The same day I was putting the final touches on my Northern Light & Power kit, my little box full of green, yellow, and red 2mm LED lights arrived in my mailbox from eBay. It was now time for my next project: traffic lights! I have two ‘T’ intersections on my layout, both of which I wanted to be controlled with traffic lights. I wasn’t satisfied with many of the commercially available light systems that are available in my area as most were unrealistic and far out of scale, not to mention expensive. The ones I did like wouldn’t fit correctly on my roads as I had built them quite narrow narrow. 

Faced with the issue of cost and adaptability, I decided to attempt my hand at building my own traffic lights. I had previously built my own track side signals so I figured traffic lights would be quite similar. My model street lights are based on a common North American style with a curved light standard which holds the traffic lights horizontally over each lane of traffic.

Six scratch built styrene traffic light face plates with visors

I started by cutting the face plate for each traffic light from thin styrene sheet. I then carefully drilled 3 – 2mm holes in each face plate, spacing each hole 1/8” apart (center to center). For the lens shades, I used a single hole punch to punch out round pieces from very thin styrene. I cut the styrene disk back 2mm from its edge, trimmed each pointy edge, and shaped each piece by gently rolling it between my fingers until it had the correct curve to fit over each LED hole in the face plate. I was able to make 2 shades from each styrene disk. I then glued 3 of these directly above each hole on the face plate.

Six scratch built styrene traffic light face plates painted black with assorted red, green and yellow 2mm LED bulbs

I masked the backside of each face plate and sprayed the front flat back as it would probably be easier to paint these prior to installing the lights. I masked the back side to prevent paint from getting on this area which would cause issues when gluing on the LED lights. I then counted out 6 LED lights in each colour (red, yellow, green) and tested each one with a resistor and power supply to ensure each one worked.

6 – 4 inch lengths of 3/36 inch copper tubing with 4 thin wire leads running through each tube

For the light standards, I used 3/32” diameter copper tubing which I cut into 4” sections. I cut the sections at 4” so I had extra length to insert into the pilot holes in my layout when it comes to installing these. I needed to thread 4 wire leads through each so the wires needed to be quite thin. I found an old computer hard drive ATA cable, which is comprised of several dozen very thin insulated wires. I then threaded 4 wires through each copper tube, one for each colour bulb (+) and a common ground (-). There were only 3 colours of wire however (red, blue, and white), so I used a second white wire that I marked with a black sharpie on both ends so I could keep track of which wire was what. 

6 – 4 inch lengths of 3/36 inch copper tubing bent to about 80 degrees to form a light standard

Once the wire leads were threaded through each copper tube, I bent the top of each tube to an almost 90 degree angle about 1” from the one end. I bent the curve over a thick marker container to keep the curve uniform and round. It’s also very important to make sure that the wire leads are preinstalled in the copper tubes, as the tube needs the internal support when bending. Without the wire leads inside, the copper tube will kink. Running the thin wire leads through the tube after it's bent is also near impossible.

6 styrene traffic light face plates painted black with red, yellow and green 2mm LED bulbs

Back side of 6 styrene traffic light face plates with red, yellow and green 2mm LED bulbs

By this time the paint on the front of the face plates had dried and it was time to install the LED lights. I first cut off the long connectors to each LED with flush cutters, leaving only a small portion protruding from the back of each LED. I then glued each LED to the back of the face plates, making sure the anode (+) connection on each LED was on the top position. You can distinguish what side is the anode connection on most LED bulbs from the curved profile on the base of the LED. The cathode (-) side is flat and squared off and the actual connection lead itself is usually shorter than the anode.

Cathode connections getting soldered together on 3 LED bulbs on the back of a traffic light face plate

Now for the fun part; soldering the connections to the LED lights. I used a small cardboard box which I cut a notch into for the front of the face plate to fit into for support. For the common (-) connection, I used one of the scrap metal LED leads I had removed prior. I spanned it across all 3 LED bulbs and soldered it to each cathode (-) connection. 

Power lead wires getting soldered to the anodes of 3 LED bulbs on the back of a traffic light face plate

For the controlled (+) connections, I carefully soldered each wire lead from the copper tube supports to the anode on each LED. I soldered the red wire to the red LED, the white wire to the yellow, and the blue one to the greed LED. The other white wire, which I previously marked with a black sharpie, was soldered to one end of the common connection i made in the previous step. When soldering the wires, I made a point of positioning each wire so it would easily exit off to one side of the traffic light. This made the back of each street light look a lot less cluttered and easy to work with.

Back side of two completed but unpainted traffic lights

Once all connections were made, I gently pulled the wire leads at the base of the copper tube supports, slowly bringing each traffic light closer to the copper post. After I had positioned each traffic light right up against the copper posts, I adjusted each light so it was positioned level to the ground when positioned upright. The wires provided enough rigidity that no glue was required to fasten the lights to the copper posts. I then painted the back side of each light, including the connections and face plate, with 3-5 coats of black enamel paint, making sure I put on enough coats that no light was visible from the back of the traffic lights when lit.

Back side of six completed traffic lights with the backs of the faceplate painted black

The final step was to paint the copper support columns an aluminum colour, for which I used Humbrol metallic aluminum enamel. With the traffic lights now complete, they only now need to be installed and connected to a traffic light controller on my layout. I am currently exploring a couple of options for controllers, including building my own. That will all however be in my Traffic Lights – Part II post, which will hopefully be up sometime this summer. For now, I will return back to my current task of building more trees. 

Six completed scratch built traffic lights with metallic silver painted light standard

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  1. I used the same technique, but used decoder wire for the three positive leads and then soldered the common lead to the 3/32" tubing and then soldered a lead at the bottom to complete the circuit. This permits using the " heavier" wire and provides a bit better support for the light head to the post.

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