chronos and lighting


I dug out my chrono just recently. It's been languishing in a corner of the garage because it's tricky to get the light right for it indoors, and outdoor opportunities haven't been great.

But looking at lighting kits got me thinking; why spend 50-100GBP on a set of lights, maybe some cheap leds would do...

So, having confirmed that the lighting in my garage is not adequate to make the thing work, I started fiddling with a couple of basic battery powered lamps.

Immediate results, in the sense of getting the chrono to detect the passage of a foam dart :). The first configuration I tried was uplighting the diffusers, by placing the lamps on the body of the chrono.
So break out the bow and put a dozen arrows through it...
First problem: it's reading too high. I'd estimate around 200 fps, it's saying 220. Light angle and shadows. The positioning of the lights is such that the shadow of the shaft passes ahead of it at the second detector, resulting in a mis-reading.
So, shift the lights, only; other positions produce random misreadings. I was hopeful about placing the lamps on top of the diffusers, but it produces a very small lit area, and you only get a reading if the shafts go through just right...

So my latest plan is to knock up a pair of brackets to uplight the diffusers from above the path of the arrows. Hopefully this will remove the shadow errors, without reducing the lit area too much.
I've got some sheet steel, somewhere, which may do (the lamps have magnetic bases).