Self Calibrating Laser Trip Wire

this is my tutorial on how to make a self calibrating laser trip wire .

WARNING lasers are super bright and will blind you. so don't use them were there are kids or in public spaces!!!

Step 1: What You Need

  • Arduino (any should work)
  • 5v buzzer (if you buy one that uses pwm you will have to change the code a little)
  • laser (i'm using one from adafruit)
  • 10k resistor
  • and a photo resistor

Step 2: Wiring

not a lot to say about the wiring, just copy the diagram

Step 3: Coding

download and run the arduino code, to program the board

Step 4: Calibration

the arduino calibrates itself at start up and when you press the reset button.

to calibrate it, align the laser beam up with the sensor like so.

then press the reset being careful not to move the laser or the board.

done, now the system should be armed. you can test it by braking the beam with you hand.

does the buzzer trigger? if so you have correctly set up the system!

Step 5: Mounting

ounce you have it working you can mount it using blu-tack .

it works best inside or in the dark. it will not work in direct sunlight because it will over power the laser beam giving false readings.

Step 6: Taking This Project Further

you can take this project further by bouncing the beam around using mirrors to make a massive laser grid.

or reprogramming it to count the number of people walking though,

or even use it for a automatic nerf gun trap!

2 People Made This Project!


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6 Discussions


3 years ago on Introduction

can some body put the code what is inside because my computer cant open it pls


3 years ago on Introduction

How would you change the code to work for a peizo sound speaker?


"it will not work in direct sunlight because it will over power the laser beam giving false readings." - Do you think it would work in direct sunlight if you used a infrared laser with a infrared filter over the photo resistor? Infrared filters block all visible light letting only infrared light pass. This approach will be harder to calibrate but it will be invisible to humans and can be setup outside for surveillance or even a wildlife camera.

1 reply

Reply 4 years ago on Introduction

you could just mount it in a shadow were the sun cant shine in on it .

but yes it would be possible to use ir although you would have to use a ir sensor