Hack a PR3000 trail camera (camera trap) to add external trigger functionality. There are 2 options, export the trigger (as a master unit), or accept it (as a slave unit). This allows multiple cameras to be connected together and be triggered simultaneously, if one of them is a master, or by an external switch.
This project is in beta, use at your own risk.
Not all trail cameras can be modified in the same way. There needs to be enough space to add the transmitter or receiver board, and there must be space to add a connector in a weatherproof manner. Here I repurpose the external battery jack for this purpose.
It is assumed that only cameras of the same make and model can share triggers, since only then can it be guaranteed that they can understand each other. In practice, I have only ever seen triggers signals that are active high, and they stay high for about 2 or 3 seconds.
The transmitter and receiver boards translate this signal between active high/pushpull internally and active low/open drain externally.
In general, the PIR sensor outputs a signal that ultimately becomes the trigger signal that will cause the camera to capture an image. The trigger signal is active high (usually 3.3V), and stays high for a few seconds (typically 2).
We want to be able to either insert our own trigger signal into the existing signal path, or read this signal. For this, we need to trace the signal path starting at the PIR sensor’s output pin.
PIR sensors are easy to identify. They are a through-hole component, in a TO-5 metal can package, with a window. They can have 3, 4, or more pins.
The BS412 is representative of this type. Here, the output pin is usually called REL (short for relay) or VOUT. The sensor contains the relevant conditioning functionality, so the REL pin outputs the TRIGGER signal to the MCU, no further conditioning necessary.
The PIR612 works similarly, except it has 6 pins. TRIGGER signal is on pin 5, VOUT.
First identify the REL pin on the PIR. Trace this pin (using a continuity tester) to a diode which will be close by. There may be an intervening low value resistor before the diode.
If the unit is to be a master, we want to connect the output of this diode to the INT_TRIG point on the transmitter circuit. If the unit is to be a slave, connect the output of this diode to the INT_TRIG point on the receiver circuit instead.
The RE200 and D203S are representative of this type. The output pin is usually called Source or Output, and the output signal is analog, not digital. If the unit is to be a slave, connect the Source pin to the INT_TRIG point on the receiver circuit (the transmitter board is not used).
The signal must therefore pass on to another chip such as the SGM8139 or BISS0001, which conditions the signal to obtain the digital trigger signal, which is routed to the MCU.
If the unit is to be a master, identify the Output pin of the SGM8139/BISS0001 (pin 2). This will be connected to INT_TRIG of the transmitter board.
In all cases, the GND point on the transmitter and receiver boards should be connected to any convenient ground pin on the CT board, and the VCC point on the receiver board should be connected to a 3.3V pin on the CT board, such as the VDD pin on the PIR.