How to sens a laser with No error?

[Shahriar]

Hi

I want to build a chornometer in an Outdoor place that when someone passes the start line the chornometer begines time measuring. the start Line width is variable between 5-10 meters. Someone told me to do the job with a laser. but the problem is the sensor for the laser. what is the best way to sens a laser with no error. In case of an error the chornometer STARTS.

ThanX in advance
Shahriar

[EdwardM]

Hi Shahriar

one way to do what you need is to have two or more beams separated by some distance so that, for example, a bird flying through one beam wont trigger the other(s).

Some other non-laser ways to achieve the same thing: It just depends how much technology you want to include...

Pressure pad which must be stepped on (or stepped off) to initiate timing.

Sound level switch, if a loud noise initiates start.

Someone looking at start line, press chronometer start button.

etc

Best of Luck

Ed

[MP]

Shahriar, What usually causes false triggers in a laser sensing circuit is the outside light such as reflections from other sources, etc. This, of course, is dependent upon what you are using for a sensor. By recessing the sensor in a tube and insuring perfect alignment of the laser, you will have more success.

MP