Derby Talk

Maximum Velocity had a good article, in their Pinewood Derby Times, on accurately determining the finish order using a timing system with photo sensors. It's a good thing to review in terms of your timing system, track and car design.

http://www.maximum-velocity.com/pinewoo ... imes-v7i2/

Interesting article.

But it failed to mention some very simple electronics to make sure all your sensors react at the same point.

Refer to: http://www.atariarchives.org/ecp/chapter_7.php

A straight edge can then be put across the track and all sensors adjusted to trigger simultaneously.

Also, while the bushing (or burying the sensor deep in the track) may help, another fix is to use a low acceptance angle sensor in the first place. For example, the following search gives sensors with 10 degree acceptance angles.

http://www.mouser.com/search/Refine.asp ... transistor*

There's even one with 8.
http://www.mouser.com/catalog/631/120.pdf

SlartyBartFast wrote:But it failed to mention some very simple electronics to make sure all your sensors react at the same point.

I think his article was targeted more towards the the lay user of a timing system as opposed to a Do-It-Yourself timer builder.

SlartyBartFast wrote:Refer to: http://www.atariarchives.org/ecp/chapter_7.php

A straight edge can then be put across the track and all sensors adjusted to trigger simultaneously.

There's a parallel port sensor system on the Internet that is essentially the same circut as that one. It also uses a potentiometer to individually adjust each lane sensor.

I don't know of a commercial timer that allows for any type of lane sensor adjustment. That's probably for good reason, as someone is likely to misadjust them and then think it is a timer issue if results don't prove accurate.

Of course, a DIYer can build such a circuit. You would then have to worry about whoever the timer gets turned over to after the DIYer moves on.