How I made my cheap ass track timer

[GoGreenLongboarding]

the most getto slalom track timer ever built is complete. I tested it with the tape switch inputs and the emergency start/stop button. (no more yelling "HEY! hit the tape!" to the bottom of the hill). It's accurate to 0.01, and didn't malfunction at all during our practice session today. The time keeper has to press a button to reset the tape switch circuit before and during your run, not a huge deal, I figure they can do that while/after seeing their time.

The idea was to wire tape strips to a stopwatch, problem being all the stopwatches I could find had start/stop on the same button, or stop/reset on the same button. I needed a way for the stopwatch to ignore the second press of the rear wheels. I read up and found a relay that could trip the timer for me, and that has to be reset before being able to trip the stopwatch again.

I built the thing for under 40 bucks, not counting random suppiles like wire/solder etc. It consists of three pushbuttons (any momentary pushbuttons will do, $6ish), a double coil latching relay ($6), batteries (2 cases for 4 AA's, 1.99ea), an LED ($2), a stopwatch ($15), and rca inputs ($4?) for tape switches, which are easily individually replaced. I had a lucky source of those, but i know there are DIY tape switches. DVD player cables can be hacked up for making connections for extra sensors, and any speaker or telephone type wire is fine for making long lines to the tape switches from the timing unit.

I made use of the second relay activated circuit by wiring in an LED that indicates the timer is reset and ready for start or finish. this light also ensures that all sensors hooked up are short free, as the timer will not release for activation if a bad sensor is hooked up. since the inputs for the tapes are RCA jacks, it would only take a minute to isolate and replace a bad sensor.

the diagram for techies:


demonstration:




Now that I've tested everything I'll make a nice enclosure. I admit the duct taped proto is pretty ugly, but who cares, I designed and built it in one day, and I've got a track timer!

P.S. you've got to be pretty good at soldering to build one of these. It's not a first timers electronics project by any means, but if you've got the skills and time it's dirt cheap. This one is single lane, but obviously an identical one could be built in the same box for a second lane if need be. also, if/when i land a stopwatch with a seperate start/stop button, i can seperate the tape strips and relay each one, to eliminate the need for the button press during the run.

[Cantee]

Thats a pretty ingenious contraption u got there! props!