DIY Simple PIR DSLR Camera Trap

DIY Simple PIR DSLR Camera Trap

I posted this to and entered it into their sensors contest a couple of years ago.  It came in second place to a high-school student who sent an Arduino up into space attached to a balloon, collected some data, and returned some incredible video.  I did not mind coming in second place to that type of ingenuity.  I learned a lot from building and writing this Instructable, mostly it gave me an understanding a how camera trap works.  I also learned that it was cheaper to purchase a commercially available product as my need for functionality quickly outgrew my hardware development skills.

This post is for informational purposes only.  I found that a lot of the optocouplers and PIR sensors had high failure rates and I was able to switch them out until I found one that was working.  Not everybody will have that luxery and the build could lead to frustration.  If anything, building my own camera trap gave me a greater appreciation for the remote and camera trap sensor vendors who provide quality products at marginally more money than this build provides.

I offer no support for this Instructable, but hope to give ideas and inspiration to those who understand the technology.

Red Squirrel.jpg

How a Camera Trap Works

The Simple PIR Sensor DSLR Camera Trap uses an industry standard PIR sensor to send a signal to a DSLR camera to fire the trigger when it detects motion. I have access to Canon cameras so this Instructable is specific to Canon DSLRs with an N3 connector or stereo connector, but this will work with all DSLR cameras that have a shutter input port. A PIR sensor is what is commonly used in home security motion detectors. Instead to tripping an alarm, we are going to use the PIR sensor to fire a camera.

Bluebird Selfie.jpg

This Eastern Bluebird was fairly predictable on where he would land, only if the yard was free of people. By placing the Simple PIR Sensor DSLR Camera Trap aimed at his perch, I could set up the sensor, set focus, exposure, shutter speed, and ISO on the camera, and walk away. This image was captured at distance of 10′ allowing for greater detail and a pleasing background blur.

Getting to Know the PIR Sensor

If you have an alarm system or outdoor lights, then you have used a PIR sensor.  They are in everyday household items and are easy to work with, inexpensive, and easily found on the Internet.


 All objects above absolute zero emit heat energy in the form of radiation. Though this radiation is not visible to human sight, it is visible to the PIR motion sensor. So the Passive Infrared Sensor uses infrared radiation to sense movement of people, animals and objects.


When movement is detected, the motion sensor’s output pin goes HIGH. This signal is transmitted through the opto-isolator (or optocoupler) to trigger the shutter button of the camera and capture the moment.


A built-in variable resistor in the PIR sensor enables you to set the duration during which the output pin remains high after retriggering. In case you want to trigger video filming with this circuit, you will definitely be able to start the video but it will only stop filming the next time motion is detected.  

This common PIR sensor does an excellent job at detecting motion and has a some features for adjusting sensitivity and timing.  Unfortunately, the pins are not labeled.

PIR pinout.jpg

Getting to Know the Optocoupler

There are many optocouplers available on the Internet.  Ebay and Amazon are great resources to purchase an optocoupler.


Pin Numbers

Locate the circular notch on the Optocoupler, this is is the Pin 1 indicator. Use the Optocoupler diagram to reference the pin numbers.


What does the Optocoupler do?

The PIR module OUT pin is connected through a resistor to an Optocoupler 4N26 that closes the circuit of the camera when motion is detected. An Optocoupler is a digital switch that uses LED emitters paired with a photo detector transistor. This means that you can use them to isolate the battery and PIR sensor from the camera connection without having any electrical contact between the two circuits.  There are many optocouplers available, these are the three that I use, all work the same.


4 Pin DIP Mounting Optocoupler PC817

Fairchild Semiconductor 4N35 Optocoupler

Do not connect the PIR and battery directly to your camera.

Building the Simple PIR DSLR Camera Trap

Simple DSLR Trigger_bb.jpg


Follow these steps to complete the Simple PIR DSLR Camera Trap. Use the fritzing diagram as a reference.

Note the the PIR sensor’s specs require 3-5VDC power. Whichever battery pack you use, make sure the volts are between 3-5VDC.

  1. Connect the positive (+) pin on the PIR sensor to the power wire on the battery pack
  2. Connect the negative (-) pin on the PIR sensor to the ground wire on the battery pack and then to Pin 2 on of the Optocoupler.
  3. Connect the signal or OUT pin on the PIR sensor to a 220 resistor and then to Pin 1 of the Optocoupler
  4. Connect the ground wire of your shutter cable to Pin 4 of the Optocoupler
  5. Connect the positive (+) wire of your shutter cable to Pin 5 of the Optocoupler.


Testing and Using the Simple PIR DSLR Camera Trap


Consider where you want to place your PIR camera Trap and determine the best settings for your location and lighting.

Rabbit and sensor.jpg

  1. Position the sensor where you want to capture an image.
  2. Use something that you can pre-focus the camera and then set lens to manual focus.
  3. Make ISO, TV, and AV adjustments
  4. Connect PIR camera trap to the camera
  5. Test that it is working BEFORE leaving.



Get down on the ground and stick your face where you think the animal will be and take a sample picture to test your camera trap. Then go check the camera and confirm that focus is sharp, camera settings are correct, and that everything works. So many things can go wrong with a camera trap: low batteries, loose connections, out of focus subjects, bad lighting, and the list goes on and on. I’ve lost more great images than I’ve captured. Also check the weather, if your camera trap is not weatherproof, make it weatherproof or bring it inside.

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