Robitronic has an affordable Lap Counting System (part#RS160). The lap counting system comes with 3 transponders, 4 receivers, interface module, receiver module cable, computer interface cable, and software for the PC. The only thing needed for the system to work it a bridge needs to be constructed to hold the receivers about two feet off the ground. Most people build the bridge with either PVC pipes or 2x2 or 2x4 pieces of wood.
The transponder system uses infrared lights for the transponder and receiver to communicate with each other. The receivers can each read about a foot width of the track. The 4 receivers that come with the system can read about a track that is 5 feet wide. If you need the track to be wider, additional receivers may be purchased separately (part#RS164). The track can be as wide as 12 feet by using all 11 receiver positions on the receiver module cable. Also, if you are running more than 3 vehicles on the track, extra transponders may be purchased separately (part#RS163).
RS160 Transponder System - Street Price is Under $400.00
RS163 Transponders - MSRP $55.00
RS164 Receivers - MSRP $46.00