As they said an IR beam, out them down a tube at each end as you want as narrow a beam as possible. Place the IR emitters on the bottom and the receivers above the track. There are piles of pinewood derby setups that use this method.
As they said an IR beam, out them down a tube at each end as you want as narrow a beam as possible. Place the IR emitters on the bottom and the receivers above the track. There are piles of pinewood derby setups that use this method.