Light barriers - 3 variations

thingiverse

Light barriers are essential tools in many experiments. They enable precise measurement of times, accurate determination of speeds, and reliable counting of events. This component is part of my project "Laboratory Equipment for teaching STEM in schools". For some parts (e.g. knobs and clamps), please refer to my other things on Thingiverse (https://www.thingiverse.com/thing:3433683). ### Components ### 24_lightbarrier_double_left and 24_lightbarrier_double_right ensure that the two light barriers have an exact distance of 10 cm. 24_lightbarrier_single is designed for a single breadboard. 24_lightbarrier_LED_mount_on_breadboard allows accurate mounting of phototransistors or LEDs on breadboards. 24_LED_cover protects LEDs or phototransistors from stray light. 24_reset_button_holder provides an easy-to-use reset button for Arduino, screwed to the universal plate. 13_universal_plate_for_electronics_new is an improved version; please see https://www.thingiverse.com/thing:3469411 for more information. ### List of Materials ### - arduino uno - max7219 dot matrix module (4x 8x8-matrix) - breadboard (SYB-170 Prototyping Board Mini) - KY-008 Laser Pointer Sensor Transmitter Module: Remove the angled plug and replace it with a straight one. Solder two single plugs to the pin holes left and right of the laser diode for stable placement in the breadboard. - Phototransistor SFH 300 3/4 + resistor 47k - LED 3mm (color doesn't matter) + resistor 330Ohm: The LED lights up when the light beam is not interrupted, helping with adjustments. - NPN transistor (e.g. BC 337) + resistor 100k at the base of the transistor - Large Push Button Cap Board Module (for an additional reset button) - Jumper Wires - wires ### Programs for Three Types of Light Barriers ### #### Lightbarrier Counter.ino #### If a light barrier's light beam is interrupted, a counter activates. #### Lightbarrier_single.ino #### With one light barrier, the duration of an object's passage is measured. Timing starts when the light beam or laser beam is interrupted (FALLING). It stops when the light beam falls back onto the phototransistor (RISING). Knowing an object's size makes it easy to determine its speed. #### Lightbarrier_double.ino #### With two light barriers 10cm apart, the duration of an object's passage is measured. Timing starts when the first light beam is interrupted (FALLING) and stops when the second light beam is interrupted (FALLING). From time duration and distance between light barriers (10cm), one can easily determine the speed of the object. This program can also be used for two light barriers farther apart (e.g., 1m).