The biggest problem I have capturing images of wildlife is not getting close enough to the subject. I never have enough time to sit and wait for them to come to me or they are easily spooked, and fly away at the first sign of movement. Using an simple, widely-available PIR motion sensor, I can leave my DSLR in the yard to capture images while I run errands, cut the grass, or even leave it out overnight.

Step 1: What Is a Camera Trap?

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 of tripping an alarm, we are going to use the PIR sensor to fire a camera.

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.

Step 2: Materials and Tools

To make this project, you will need the following items.

(1) PIR sensor from Radioshack or Adafruit.
(1) 220 resistor
(1) RN3 cable - I used this one: Canon RS-80N3 Shutter Release Remote Switch
A quick check of Amazon lists this Canon RS-80N3 Remote Shutter cable for quicker shipping, although I haven't tested this one.
(1) breadboard
(1) Philmore (3) AA Cell Battery Holder, standard snap terminals
(1) Optocoupler 4N26
Wires to make connections
(1) box to house PIR sensor, and battery pack

Tools

soldering iron
glue
multimeter
drill

Step 3: Canon N3 Shutter Cable

Canon uses a propitiatory cable to its high-end DSLRs for remote triggering. Ebay and Amazon are full of remote shutter release cables that you can modify for this project.

Remove the screws on the shutter release cable plastic case
Remove the screws holding the motherboard in the case
Remove the motherboard form the case.
Desolder, cut, or otherwise detach the cables from the motherboard
On this cable, we are interested in the Red (Photo) and Yellow (Ground) cables, as shorting these cable, or touching them together, will trigger the camera. Other shutter release cables from different manufactures use different colors. Most boards are labeled.

The shutter release is basically a couple of contact switches. Connecting the focus pin to ground and the camera will focus, while connecting the shutter pin to ground and the camera takes a picture. For our camera trap. we will create a switch to connect the ground pin to the shutter pin to take a picture when motion is detected. We could do this directly to the camera, but if something goes wrong, you can damage your camera, so make sure we use an Optocoupler described in the next step.

Step 4: Getting to Know the Optocoupler 4N26

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 it 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.

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

Step 5: Building the Simple PIR Camera Trap

Assembly

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.

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

Step 6: Using the Simple PIR Camera Trap

Installation

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

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

Testing

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.

Step 7: Finishing Touches

You will want to enclose your electronics in a weather-proof enclosure if you are using it outside. I'm constantly modding my cases, but Radio Shack project cases and Harbor Freight ammo cases are great starting points. Pelican cases and even Tupperware cases are great for Simple PIR DSLR Camera Trap photography.

I usually place my sensor on paths, trails, or logs where I pre-focus the camera. I don't want movement from outside the path to trigger the sensor, so I added a tube to the end of the sensor so it picks up movement directly in front of the sensor. I started using toilet paper holders, then found some plastic tubing that is weatherproof and keeps the sensor out of the way.

Nighttime images require the use of off-camera flashes or strobes that are beyond the scope of this Instructable.

Step 8: Sample Images

The Simple PIR DSLR Camera Trap allows me to capture images that otherwise would be impossible for me to capture. These images are captured in the early morning hours where I'm sleeping and the critter is comfortable enough to cross through my sensor. If I was physically there waiting for these images to happen, I'd still be waiting.