Thingiverse
Light barriers - 3 variations
by Thingiverse
Last crawled date: 6 years ago
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 impractical, so I have a larger reset button mounted on the holder and screwed to the universal plate.
13_universal_plate_for_electronics_new: improved version, please see https://www.thingiverse.com/thing:3469411 for more information
List of material
arduino uno
max7219 dot matrix module (4x 8x8-matrix)
breadboard (SYB-170 Prototyping Board Mini)
KY-008 Laser Pointer Sensor Transmitter Module: This module is very often offered with an already soldered angled plug. This angled plug must be removed and replaced with a straight plug (soldered on the underside). I also recommend soldering two single plugs into the (slightly too large) pin holes left and right of the laser diode. Then the module can be placed very stable in the breadboard.
Phototransistor SFH 300 3/4 + resistor 47k
LED 3mm (color doesnt matter) + resistor 330Ohm: the LED is on when the light beam is not interrupted (this is very helpful for the adjustment.)
NPN transistor (e.g. BC 337) + resistor 100k at the base of the transistor
Large Push Button Cap Board Module (if you want another reset button)
Jumper Wires
wires
Programs for three types of light barriers
Lightbarrier counter.ino
If the light beam of a light barrier is interrupted, a counter is activated.
Lightbarrier_single.ino
With only one light barrier, the duration of the passage of an object is measured. If the light beam or the laser beam is interrupted, the time measurement starts (FALLING). Timing stops when the light beam falls back onto the phototransistor (RISING).
If the size of the object (e.g. the length of the car shown in the pictures) is known, one can easily determine the speed of the object.
Lightbarrier_double.ino
With two light barriers, which are built at a distance of 10cm to each other, the duration
of the passage of an object is measured.
If the first light beam is interrupted (FALLING), the time measurement starts.
Timing stops when the second light beam is interrupted (FALLING).
From the time duration and the distance of the two light barriers (10cm), one can easily determine the speed of the object.
Of course, this program can also be used if you want to position two light barriers farther away (for example, 1m).
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 impractical, so I have a larger reset button mounted on the holder and screwed to the universal plate.
13_universal_plate_for_electronics_new: improved version, please see https://www.thingiverse.com/thing:3469411 for more information
List of material
arduino uno
max7219 dot matrix module (4x 8x8-matrix)
breadboard (SYB-170 Prototyping Board Mini)
KY-008 Laser Pointer Sensor Transmitter Module: This module is very often offered with an already soldered angled plug. This angled plug must be removed and replaced with a straight plug (soldered on the underside). I also recommend soldering two single plugs into the (slightly too large) pin holes left and right of the laser diode. Then the module can be placed very stable in the breadboard.
Phototransistor SFH 300 3/4 + resistor 47k
LED 3mm (color doesnt matter) + resistor 330Ohm: the LED is on when the light beam is not interrupted (this is very helpful for the adjustment.)
NPN transistor (e.g. BC 337) + resistor 100k at the base of the transistor
Large Push Button Cap Board Module (if you want another reset button)
Jumper Wires
wires
Programs for three types of light barriers
Lightbarrier counter.ino
If the light beam of a light barrier is interrupted, a counter is activated.
Lightbarrier_single.ino
With only one light barrier, the duration of the passage of an object is measured. If the light beam or the laser beam is interrupted, the time measurement starts (FALLING). Timing stops when the light beam falls back onto the phototransistor (RISING).
If the size of the object (e.g. the length of the car shown in the pictures) is known, one can easily determine the speed of the object.
Lightbarrier_double.ino
With two light barriers, which are built at a distance of 10cm to each other, the duration
of the passage of an object is measured.
If the first light beam is interrupted (FALLING), the time measurement starts.
Timing stops when the second light beam is interrupted (FALLING).
From the time duration and the distance of the two light barriers (10cm), one can easily determine the speed of the object.
Of course, this program can also be used if you want to position two light barriers farther away (for example, 1m).