TRACK SENSORS
Regardless if you are building your own project or purchased it already built, you will still have to prepare the track that you will be using. There may be several different styles in track design, so you will have to improvise to what works best in your situation. I can only show you the way I did mine, but there can be several methods to achieve the same results.
If your track allows it, router a 3/4" slot underneath the track finish line about half the thickness of the track. If routing a slot is not desirable, then try mounting one or two furling strips of wood underneath the track to act as a guide. This will allow room for the sensors and a place for the wires to run. Note: There are several methods that can be used to mount the phototransistors. It just depends on how much time and effort you want to apply. Just a simple hole can be drilled thru the track for the sensor and merely pushing the sensor in the hole. What ever works best for you. Drill (4) holes evenly spaced in the lane centers along the same line as the slot on the underside. The way I did mine was to drill (4) 3/8" holes and I used the 3/8" lamp 'all thread' brass tubing by cutting the same depth from the track surface to the top of the slot. Use a hammer and hit the all-thread pieces into place until flush with the track surface. Apply heat shrink to the leads of the photocells making sure to mark which is the collector and emitter leads. Also mark which lanes numbers are which. I then used a LED holder by slightly removing some of the collar bead, installed the Phototransistor and shoved that into the all thread tube. This way the sensors can be easily removed. I slipped the LED holder over a thin grinding stone and used it in a Drummel tool and ran it against some sand paper. It should look something similar to this. When done, the phototransistors should be about 1/8" below the surface of the track. Any less and it might pick up false triggers and any more might cause improper responses to the exposed light source.
Now is the time to wire the DB9-2 cable to the Photocells. You will be using 5 wires in the DB9-2 cable. Use this diagram and follow the same wiring scheme as before. Very important- pay close attention to which is the collector and emitters on the phototransistors. Normally the short lead is the collector. Be careful when using heat shrink with the heat gun because the frail insulation on the cat5 wire melts easily. Tuck the wires in the track slot carefully. Use a cable clamp to secure the cable to the track end (see in photo). You might want to cover the slotted bottom with duck tape or thin cardboard when finished.