BirdBox infra-red camera IR filter upgrade

Now that the bird nesting season is over, it's upgrade time! The infrared (IR) cameras in this year's boxes are getting IR filters...

and some to spare...

This year's two new bird boxes have an infrared (IR) camera with visible and IR LEDs (Robin box Birch log tit box).  There is 'night mode' with IR light  that the birds cant see, and day mode with optional visible light illumination. All non IR-light sensitive cameras have an IR filter built into the camera, whereas IR-sensitive cameras don't.

Without an IR filter, IR camera images have a pinkish cast to them in visible light, giving a permanent 'Hipstamatic' look:

Un-filtered IR camera pink colour is obvious here

An IR filter (called an IR-cut) converts an IR-sensitive camera into a conventional one that can't see IR light.  This gizmo has a bit of glass in it that blocks IR light, and can move backwards and forwards over the camera lens by changing the voltage polarity applied across it.

These bird boxes use the 8MP Raspberry Pi IR camera board.  This has a similar shape and design to those found found in many commercial CCTV cameras, so IR filters designed for CCTV camera modules can be fitted to them.  Sort of...

My first attempt to do this was the top-down camera in last years's double camera bird box.  Unfortunately, I sourced an IR-cut that had an ?M12 lens mount on it, basically a dirty great chunk of plastic poking out the font that needed to be cut off before I could use it = fiddly.  You can see my v1 test for this here from a separate project:

I wanted something easy to add to this year's boxes, and found an IR cut filter without a lens mount which fits nicely over the existing screw holes in the Raspberry Pi camera module (22mm separation).

This come from AliExpress (China, so take a couple of weeks to get to the UK), and costs $3.50 so wont break the bank.  It comes with a separate lens mount holder which I haven't used.  There's the option of 20mm or 22mm screw hole separation at order - you need the 22mm one as to fit the Raspberry Pi camera board.

This shows the underside of the camera unit that is slotted in to the top of the birdbox, pre and post IR-cut upgrade. The ir-cut is attached over the camera by M2 nylon screws and nuts, and the screws just go through the 4mm ply and pass through the camera board.

IR-cut sitting flush against the 'underside' of the bird box camera insert

I had previously designed this year's Raspberry pi zero W add-on board with an IR-cut in mind.  The voltage polarity reversal to switch the IR-cut is done with a L293DNE (£2.70).  I did  a more detailed writeup of this here which also has some example code.  The design for the wiring of this my customised add-on board is detailed here.

No birds in this, but you get the idea what switching the IR-cut in natural daylight does...

...so there are alternatives to this, eg here which has integrated IR LED, camera and IR cut - does not have stellar reviews on amazon though.

WiFi Robin Nest Box

I've planned a 'hub and spoke' arrangement of bird boxes.  I previously described the 'Wireless Access point' box (aka 'WAP box'), this post details a 'spoke/satellite' box.

Robin box in the undergrowth

Robin box with Great tit...

This is a ground-level open-fronted box designed with robins in mind.  Last year, a robin family successfully raised a brood of three chicks about a meter away from this new box at ground level.  That nesting site has since disintegrated, so this is hoped to be come its successor.

The camera setup is designed to be generic so that I can remove it and swop it into other boxes designed with similar dimensions, in that way I can maximise the number of boxes, while not having to equip every one with a camera.

There is a ledge at the top that holds the camera section.  This consists of a Raspberry pi Zero-W, an 8 megapixel v2 'Pi-Noir' camera (sensitive to IR as well as visible light).  Underneath are 4x each of white and IR LEDs for illumination.  Power is via a 12v feed from the WAP-box, dropped to 5v via a recom r-78b5.0 1.5 switching regulator.  LEDs are powered form the same 5v source, and switched via a transistor array (ULN2003AN), on the R side of the picture below.  This allows low, medium and high setting on each of the IR and visible light, white LEDs.  The unoccupied left side slot is wired for a L293DNE to switch an IR-cut filter (to be added at some point later, for a how-to see this post).

The white LEDs are wired in parallel with a 50ohm resistor for each LED.  The IR ones are also in parallel, but with no extra resistors.

The circuitry is arranged on a commercial prototyping board designed with the same dimensions as the Pi zero-W.  The board layout is as follows:

Protoboard layout, same footprint as Pi Zero/W

I also added pins for a DS3231 real-time clock module, since the Pi is only able to get time from the network, and wanted to plan for occasions when it loses network connection (there's not enough headroom in the box to fit them on the actual GPIO pins).
As with most of my other boxes, video capture is via motion capture software pikrellcam with captured footage/images saved to a mounted network drive (i.e. off the box).

This clip shows the box in situ cycling through various illumination settings:

A couple of observations from the transition from 'testing to the real world...'
Pi Zero-W wifi reception once closed into a wooden box drops off somewhat.  Running the following command gives some idea of reception levels:  iwconfig wlan0 | grep -i --color quality
Output is: Link Quality=44/70  Signal level=-66 dBm

The impact of this is that I cant set PikrellCam to record video captures direct to the network drive, as it all keels over.  Handily there is an archive option, so I just need to keep an eye on it and archive to the network when need be.  I also dropped the quality of the live stream which seems to have stabilised it. 

UPDATE: A updated implementation of this kit is detailed, in 'Birch Log' nest box described here