It's been many a year since I've messed with electronics -- back when a nice color television used maybe a dozen 6GH8A vacuum tubes. (Good riddance!)
Anyhow, what I have in mind is a low-cost timing setup, used to measure the time between two events -- both of which would be the interruption of a light beam. Extreme accuracy isn't necessary -- 0.01 seconds would be fine, so no high-speed industrial stuff needed.
I want to measure the amount of time a motorcycle rider uses (without touching a foot to the ground) to cover a fixed distance, riding as slowly as possible, for perhaps 20 feet. In other words, a 'slow race'. You'll see these at various biker events, and it's a whole lot tougher than it looks. Here's the best I've seen in a long time:
I'm thinking of two pair of tripods, one for the start line and one for the end, with each pair holding an opto-electric device and a reflector.
The cheapest opto-electric devices I can think of are the safety units that automatically reverse a garage door opener. I have a pair (from an old dead opener), and they're pretty cheap on eBay. The problem with these is, I can't find any source of information about how these operate. Perhaps it's deliberately arcane knowledge, so that it's difficult to defeat their purpose.
Does anyone have a link or source of info on how I could use these critters to my purpose? Or, for that matter, a simpler, cheaper way to do the job accurately? I've seen timing kits specially made for racing, but they're asking about $600 and up. I'm thinking of a small fraction of that.
I also found these, after about an hour of web searching:
... but it's hard to tell how much useful information they'd come with.
I haven't decided on what to use for the actual timer & output, but that might be the simplest part.
(One guy suggested pneumatic switches. Old-timers like me can remember when gas stations had hoses draped across the pump lanes which, when run over by a car tire, would ring a bell inside the station. They had these antiquities called 'attendants' who would come out and put gas in your car. Honest. Then they'd clean your windows. Nobody believes me, but it was very common back when 6GH8A's were about $3.50 a copy...)