Lane Sensor Hookup

The lane sensors should be mounted below the track, recessed so that only the light from the LED directly above hits it. (Assuming you are using sensor illumination LED's. If you are not using per-lane LED's then be sure each sensor is well illuminated.) Either way, be sure that no stray light enters the sensor except from above. The sensor should be completely blocked from light when a car passes over it to insure it can detect a car instantly upon crossing the finish line. Exact mounting details are left up to the installer, due to the wide variation in track designs. Scroll down to the bottom of the pages for some photo examples of a cross-section cutaway view of a sensor installed in a wooden track.

An individual wire runs from the collector (short lead) on each individual phototransistor to one of the lane pins on connector J4.

The long lead of the phototransistors all connect together and to the ground pin on connector J4.

You probably want the wiring to the sensors extra long, as they are usually mounted beneath the track and the rest of the electronics is usually in the tower part of the finish line.

This is a really long 4-lane sensor harness:

These are a couple of track cross-section cutaway views of a recommended sensor mounting. Note that it is recessed with the inside of the hole painted flat black. Painting can be done by soaking a brush or cotton swab with flat black liquid paint and running it through the hole. A few people have also had success spraying into the hole from below with flat black spray paint. Do not use gloss paint. The flat black paint prevents stray light from bouncing off the sides of the hole into the sensor.
Sensor Track Cross Section

Make sure that no paint or glue obscures the upper area of the sensor, and that the sensor is in straight and aimed precicely at the light source. Also make sure that no light comes into the sensor from below.