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Topic: 100m race timer (Read 1 time) previous topic - next topic

apophis13

Jun 16, 2009, 05:50 am Last Edit: Jun 16, 2009, 05:50 am by apophisadair13 Reason: 1
Hey all! ;D

I want to make a 100m race timer with a sensor to sense the start and a sensor for the finnish, i was thinking of shining a Laser into an LDR and measuring someone run through the laser that way? what do you think? and how will i send data from 100 m away? any ideas?

Thanks

Grumpy_Mike

Yes a laser sounds good. However, you might want to pulse the laser and use a photo transistor and amplifier to minimise interference from ambient light.

As to getting the signal over the distance, I assume you don't want to run a long wire so I would guess that wireless would be the best. Just a straight forward TX and RX would probably do.

apophis13

Thanks, just a another question, why pulse the laser?

AWOL

Quote
why pulse the laser?

So that you can distinguish it from constant sunlight more easily.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

apophis13

Will just shielding the sensor work...?

Grumpy_Mike

It might, being a laser you could put the sensor at the end of a tube but it is more tricky to set up and you still have some problem with stray light.

apophis13

Do you have any other suggestions for detecting a person running past a specific point?thanks for the help

Grumpy_Mike

How about a web cam running some image processing software. You only need look at a small vertical bar of the image to see if something has moved and trigger the timer.

whgibbo

I'm looking to do something similar..  I saw this on you tube, Laser Tmer version

But wasn't sure what bits of equipment I would need.  I'm new to electronics, but not to programming..  Any advice?

Thanks

apophis13

What kind of accuracy should i expect? and how long will the wireless signal take to register, approx?

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