Light barriers - 3 variations

Light barriers are usefull in many experiments. They are needed to measure times, to determine speeds or to count events.

This components are part of my project "Laboratory Equipment for teaching STEM in schools" . For some parts (e.g. knobs and clamps), you can see in the pictures, please look at my other things (for example https://www.thingiverse.com/thing:3433683).

### Components ###

24_lightbarrier_double_left and 24_lightbarrier_double_right: These parts guarantee that the two light barriers (I prefer small lasers) have an exact distance of 10 cm.

24_lightbarrier_single: just for one breadboard

24_lightbarrier_LED_mount_on_breadboard: This allows the phototransistor (or a LED) to be mounted very accurately on the breadboard.

24_LED_cover: This cover serves to protect the LED (or the phototransistor) from stray light.

24_reset_button_holder: Sometimes it is necessary to reset the counter or restart a program. The reset button on the Arduino is somewhat impr