Self Timing Systems: Build Notes

I've written previously about my intention to mount a stopwatch onto the deck of my board in order to give me an idea of timings at next Saturdays downhill competition.

Far from being hard to do, I still managed to cock-up a few bits and thought that a few pictures might demonstrate just how easy it should be (in principle) and from this, just what possibilities are, erm, possible.

I started by mounting a push switch onto the end of the brake handle as shown below.  As the brake lever won't be required for either the start or finish, I should be able to start and stop the clock without having to do too much all at once.  If there is a starting gate to pull out of, this may be a little tricky, but I won't know until the day.  

Wires run from the switch, through the brake handle and out through a side hole that also has the hydraulic hose running through it.  This is then secured in place with a cable tie with plenty of wire (about double the length of the handle) inside the handle in case I need to pull out the switch or the cable snags.

The wire then runs down the hydraulic hose, secured together with alternating cable ties and electrical tape before running onto the deck and into the stopwatch.  Again, excess cable is looped together at the bottom of the hose for possible modification later.  If nothing else, a connector to remove the stopwatch from the deck may be useful in future.

The sides of my stopwatch are removable and are large enough that a 2mm hole can be drilled allowing access for the cable push through.  From inside, lots of black wires can be seen linking the front-side pushbuttons to the main circuit board.  I've stuck to the back of the LCD screen a couple of low profile junction connectors that in theory allow me to snip the start/stop wires and reconnect allowing for hijacking with my new push button.

I say in theory, because this is where I made my cock-up by a) making a huge presumption on which wires to intercept, and b) accidentally chopping through one of the wires making it too short to reach.  I now have a stopwatch that can only be started via the brake handle and can only be reset by the front panel.  Hey ho.  No biggie and I could have simplified all of this by just soldering a couple of points.  All very well, but every time I solder, it looks as though I did it wearing boxing gloves - blobs of solder everywhere.

What I have been looking out for are either a slimline version of these cable hijackers (as shown below) that connect one wire onto an existing wire simply by clamping the top shut, or something similar.  Any suggestions much appreciated as these are far too fat for this application.

On the back of the stopwatch, I removed the clip/magnet and chopped off a couple of raised sections in order that the back of the unit was relatively flat.  From here, the stopwatch can be easily mounted to the deck using my favourite bodging solution - industrial Velcro.

Next up, testing!