Openthing 2 - RepTrap

Openthing 2 RepTrap is a detection device and camera trigger for capturing images of relatively small animals, including lizards, frogs etc.

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The Rep Trap idea is a hardware system designed to overcome the limitations and challenges of conventional trapping methods. Inspired by PIR sensors commonly used in wildlife cameras, the hardware system features a gate-like sensor arrangement, specifically designed for animals to pass through. Positioned with its sensor element facing downwards, the system incorporates a distance measurement unit within the sensor. This unit continuously measures the height below the sensor, detecting any changes in height.

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In the field of animal research, the traditional method of capturing small animals often relies on traditional pitfall traps. These traps typically consist of a container such as a bucket that serves to capture the animal and long tarps attached to each side to create a funnel-shaped structure to guide the animal into the trap.

However, this approach poses significant challenges and potential risks to the captured animals. One major concern is that the captured animal remains trapped inside the trap once captured, making it vulnerable to attacks by other animals in the vicinity. In addition, adverse weather conditions such as heavy rain can flood the trap and increase the risk of drowning for the captured animal if it cannot be checked in time.

Another disadvantage of this trapping method is that it relies on animals voluntarily entering the container, which not every animal is tempted to do. This poses a significant challenge for researchers, as some animals may not fall for the trap and may fail to enter the intended container, resulting in missed opportunities to study and monitor these shy creatures.

The Openthing 2 RepTrap is intended to address this problem and provide an alternative to traditional methods.


Conventional motion sensors rely on temperature difference detection using infrared sensors. The environment is divided into small segments, and the temperature difference from one segment to another is detected when a warm object moves through the sensor's field of view. Due to the segmentation and the requirement for a distinct temperature difference from the surroundings, these objects need to have a certain size and temperature contrast to be detected. Reptiles such as frogs, lizards, or snakes usually have minimal temperature differences compared to their surroundings and are not large enough to trigger the sensor's segments.

Our approach does not focus on motion but rather on the height of an animal, regardless of whether it is warm or cold-blooded. The RepTrap monitors the distance in front of the device using infrared laser sensors. When the height under the sensor changes, the sensor detects it and sends a signal to activate the camera. Installation only requires setting up a gate-like structure that the sensor can monitor, eliminating the need for holes and buckets.

This installation can remain unattended at a location for several days without putting animals at risk. The animals are not confined, reducing exposure to risks such as rainwater or other predators. With this solution, this type of trap can also be set up in remote locations where daily trap checks may not be feasible.

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  • 1 × RP2040 Raspberry Pi Microcontroller
  • 1 × W25Q128JVS 16MB Flash (holy moly)

  • RepTrap ESP32-S3 Variant

    Mirko02/12/2024 at 10:57 4 comments

    I decided that I do not like the RP2040 anymore and exchanged it for the ESP32-S3. With the ESP32 I get BLE for this device, which can make it into a remote trigger as well but mainly it will be possible to set configurations for the sensors sensitivity!

    The power consumption of the ESP is also lower in deep-sleep where I was not able to get the RP2040 into a very nice deep-sleep tho. Another benefit is the OTA functionallity I am getting which makes the device updateble very easy. 

    I also added a USB Detect to see if a USB is connected or not, that way I can handle the code differently for examply only start BLE advertising if USB is connected or checking for a specific WiFi to download firmware updates.

    I also fixed all issues I found with the first Version, moved all connectors to one side to make it easier to be added into an enclosure, I added mounting holes to secure the PCB and I even left some space to add another output to be triggered which could trigger two different cameras at the same time. The connectors are now also on the horizontal sides of the board to free the short side of the device for mounting options like holes on the enclosure etc.

    Another very experimental change was a Hall effect sensor DRV5032FB as a switch for the device! I want to achieve a IP68 waterproofnes with this device (I also exchanged the USB and the other connector to be IP68). The idea is instead of a classic switch or push-button which needs a hole in the enclosure I add a hall sensors and put a mechanical switch from the outside including a magnet. It hopefully will feel like a real switch but has no contact to the PCB - that way this switch will be 100% waterproof! and the only gaps I have are for the USB and klinken connector. Lets see how that idea works out. 

    The device also got a RGB LED to show its different states it can be in or show errors. The USB Port is also connected to the ESP32 USB which can be benefitial later.

    If you read this please comment +1 

  • Looking for support

    Mirko10/12/2023 at 07:14 0 comments

    Hello there!

    I'm conducting research to gauge the level of interest in this project. To achieve this, I'm in the process of gathering email addresses to compile a list. This list will help me maintain an overview of individuals who are interested and whom I can also directly update on project status.

    If you'd like to support the project and stay informed, please consider adding your email address to the list by visiting this link:

    Thank you for your interest and support!

  • Field Test

    Mirko10/08/2023 at 07:58 0 comments

    Last week I printed a smaller case for the RepTrap and tried to set it up how it should be setup. Unluckily I did not catch any animals with it. I tried to set it up to catch some birds because they are more likely to appear, but had no luck. I witnessed some birds approaching the bait but I think they have been just scared due to the camera and the sensor. They have been close and one should have been inside the field of view but was to quick. It actually needs some time for the sensor to detect an object, the settings are 80ms measurment and 100ms sleep (which is already pretty fast and not very battery friendly) my initial setting was 100ms measurment and 300ms sleep. It is getting cold already outside and so there are not many animals to be photographed. 

    But here are some images of the setups

    Watch that hole
    The sensor can be setup to monitor the entrance to a home
    Also bird watching can be managed with it but this little guys are super fast!
    LOOK! A LIZARD... yea okay.. it is a fake one. One day my friend! one day!

  • Prototype Adventure

    Mirko08/15/2023 at 14:39 0 comments

    I received all components including the 0402 parts (which I never soldered before) and on Monday I also received the PCB (made by Aisler).. so it was time to test my soldering skills and eyesight.

    Spoiler: both are crap! But I made it! After a couple of houres I got the first prototype of my RepTrap in my hands. I will let the images and video talk for themself. Second spoiler: it was working on the FIRST try! (almost)


    and it is PUNCHING FAST!

    Mistakes I made (of course there are some)

    1. forgot to add pull-down for the LDO enable pin
    2. connected the status LED to BATT+ instead of VBUS (which made them glimming even if the edvice was off)
    3. the optocouple was not working with the 220R I added to prevent to much current to flow. But somehow even 100R did not trigger the camera... I removed them and then it fully opened the coupler. Not sure if that is the right way.
    4. the 18650 Battery Holder was made for the extended version of an 18650 incl. protection circuit but I don't have such a battery and also realised that they are super expensive.

    Everything was fixable! and now it already works super nicely! But now I have to do some more coding.. but I am very proud of that thing. I hope I can test it soon in the real world to see if it really does what it is supposed to do! Stay tuned

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