Phototransistor digital read

Other Hardware Sensors
1

Sup guys

I’m currently working on a ping pong cannon that uses a red laser and photo transistor to measure the speed of the projectile. I used analogRead to and micros to measure the time where the brightness dips since I cannot block out the light hitting the PT 100%. Also the analog can only measure in ~100micro seconds where i need <40 micro seconds.

Digitalread measures fast enough but then I get a 1 or 0. How can I make the dip in brightness show up as a 0 since the PT gives a 1 when the laser shines on it? Ive used 10K and 100K resistors to increase the sensitivity but to no avail

2

Modulate an IR signal and use a TSOP type sensor to read it. Digital output, very fast and reliable, not affected by ambient light unless in really bright sunlight or so..

Or even easier: get a simple break beam sensor. Those are meant to do just this.

3

Thank you very much. I will go look for theese things