Hopefully you already know the two ways of triggering: active IR (light barrier) and passive IR (motion detector). From both systems you will find different products on the market, and I tested some of them.
1. eltima jokie
The man behind eltima is a german electronics engineer and he built a great light barrier for ultra high speed photography. That means bullets, wasps, flying birds and so on. It is a light barrier with sender and receiver in one tiny little housing and on the opposite side there is reflector reflecting the IR beam.
The main problem is: battery life! With 4 AA you will get 7 days of a working system. You could place a car battery in the forest. But then you have a tiny little light barrier and a ultraheavy battery for using it like for 8 weeks or so. Doesn't make sense.
As I already mentioned, the system is based on reflecting the beam by a triple mirror from up to 10m distance. That works fine. For tiny little things. Insects, rain and birds will trigger it. Snow, rain or bees will drive you crazy with this system and the high sensitivity. Your memory card will be full or the flash batteries will be empty.
When you add a 4 D-cell battery pack you get up to 4 weeks battery life. One thin you have to do, is hack your camera cord to the sensor to remove the wakeup mode that will wake the camera from standby every 5 minutes. If you need ultra short trigger times, you found your system. Bats, birds, mice and insects are the target species of that. For my work, this is simply not the right gear. But it's small and tiny and for a overnight setup it might be great.
Price tag: around 150 €.
2. Trailmaster TM1550-PS
Famous Trailmaster has been used by famous photographers like Steve Winter for long term cameratraps. Snow leopard, bears, tigers and so on have been photographed with this system. The high price of 390 USD + customs and shipping is worth it. You will not mange to destroy it! My systems have been under the snow for weeks, felt in the water, got cold and hot and worked all the time. An amazing tool!
Its an active infrared light barried with two black boxes: a sender and a receiver. At the receiver you get the opportunity to set beam interval, number of photos per trigger or two blocking intervals to stop the system working at a specific day of time. You will need 2x4 baby cells and they will last up to 6 months. Quite a fun to work with! Mount the boxes on two opposite trees or posts and let them do their work. What I really love about light barriers is that you get the photo of the animal exactly in place where you need it.
The trailmaster is the most reliable system but also the most expensive on. It's really sad that the company doesn't make them a bit smaller. With actual PCB printing techniques that would be easily possible.
3. Snapshotsniper 2
Americans are famous for their DIY culture and so they do with trailcameras. Why should you spend a lot of money for a cameratrap of you can build it on your own from old cheap digital cameras and some walmart plastic boxes? This is why the Snapshotsniper 2 was invented. Gary, who invented it, is hunter and placed a very interesting system on the marked. Its a tiny little PIR sensor based on a Picaxe micro controller. You can buy it with preinstalled software or you just get away with your own code in the picaxe editing software. Easy! Do whatever you want with your own code!
There is a switch to decide between two programs, like one with many pictures per event and one with only one picture per event.
The only problem: there is no box on the market for the Snapshotsniper 2 and you have to build it on your own. It might be difficutl to get it waterproof. And there is a potentiometer on the board which get corrosion problems very easily. One drop of water could disturb the whole system.
I really like to have the opportunity to place the sensor directly in the camerabox. It's easier for quick setups!
Batteries are 3.3V lithium batteries and last for minimum 12 months. IF you have a box for it, then its just amazing and almost as reliable as the Trailmaster. The sensor doesn't care about sunlight or movement of plants. Even insects will be ignored.
And now: the price! It's just 50USD per unit and that's why it is my favorite for camera trap sensors.
4. Camtraptions Trigger
Will Burrard-Lucas decided to invent his own Camtraptions trigger. It's a ready to use PIR sensor developed for the work with DSLR cameratraps. It has a lot of programs and with combinations of dipswitches you get everything you need. But to have many choices makes you think what will take some time on location. My experiences: quite good until now!
You need 6AA Batteries and they will last for up to 3 months. The housing is very strong, but the sensor is very sensitive for everything. I get a lot of false triggers. Rain, mice, insects. Humidity will not be a problem. I love the different program options. The best thing is the bulb option to trigger the camera for some minutes, what is great for star skys or similar low light sceneries.