By: Michael Dempsey
While we have been waiting for circuit boards for our Tiny Railroad Crossing Controller to arrive, we have been hard at work developing our next product; the Tiny Traffic Light. The Tiny Traffic light is an operational scale model traffic light head for use on model railroads and dioramas. This product is designed to work seamlessly with our Tiny Traffic Light Controller! We have developed traffic light heads for HO scale (1:87) and for N scale (1:160).
The first step in the development of these lights was to design the circuit boards. These are extremely simple boards, with the pads to mount the LEDs on one side, and pads for soldering the wires on the other. Once these circuit boards had been made at a PCB fab house, we used a reflow oven and solder paste to solder the red, yellow, and green LEDs in place.
Once the LEDs have been soldered to the boards, we prepared the foot-long wires for each traffic light head. Each light has four wires; red, yellow, green, and black for the common ground. Once the wires were soldered and the lights tested, the traffic light heads were ready to be cast in resin.
While we were designing and assembling the circuit boards for the traffic lights, we simultaneously prepared to cast these lights. We started by machining a 3/4″ thick block of plastic into the positive shape, from which we would create a mold. This positive features 12 HO scale traffic lights and 12 N scale traffic lights. Each light is a solid rectangle with shallow dimples where the individual lights would be positioned. We left out the hoods over the lights to make the lights easier to see once the traffic light was installed on a model railroad.
From this positive, we cast a silicone negative mold. This process went extremely well, even without a vacuum chamber. There are only a few minor defects in the mold, none of which make the mold un-useable. With this mold in hand, we could then cast the resin traffic lights. We used a simple resin, tinted yellow. After dispensing the resin into each mold, we inserted an assembled circuit board into each one. This way, the circuit board is encased in resin, making the traffic light one finished assembly! The resin also acts as a strain relief for the power wires, reducing the risk of accidental damage.
It was extremely refreshing to try something new with these Tiny Traffic Lights. While we have had experience with casting, electronic assembly, and CNC routing, this was the first time we combined these separate skills to produce a finished product! We are extremely proud of our Tiny Traffic Lights, and look forward to listing them for sale on our website very soon!
Fellow model railroaders, be prepared for four additional new products from D5 DEM. We are in the design and prototyping phase for several different products which will being new levels of realism to the model railroading hobby. Stay tuned!