Sunday 27 January 2019

LED backlights for birdbox illumination

All my birdboxes have Infrared (IR) and white light illumination, using 5mm LEDs.  The IR ones that I use give nice diffuse lighting, however the  white light ones tend to give a 'spotlight' effect.  I spotted these LED backlights recently from Pimoroni and once installed, they give a nice diffuse 'daylight' effect:

Underside of roof camera insert.  The circular black thing is an IR-cut module.

This year's new small bird boxes are equipped with two each.  They are wired in parallel to 5V with a 50 ohm resistor for each one, as well as another 50/100/200 ohm resistors between the ground and the uln2003 i/c transistor that is used to switch them for low/med/and blinding light levels.  Default is medium.

This picture shows the underside of the roof 'insert' for this small birdbox.  To the top and bottom are 5 IR LEDs in total.  These are wired in parallel, the only resistors are between the ground and the uln2003 (same arrangement as above there).  100 ohm seems the sweet spot.

The IR LED setting is still a bit spotty for my liking.. but I haven't found an IR led panel.... 
Last year's version of this used 4 IR LEDs, on in each corner, leaving a dim bit in the middle... which is exactly where all the action is... I fixed this this time by adding a fifth LED that points a the middle specifically.  The camera is rotated by 90 degrees to include the entrance hole in the image as well.  A 3mm green led indicator is added via one of the GPIOs (+10k ohm resistor) so that if I cant connect to it, it's obvious from the ground that there is/isn't power.

The diffuse white LED is an improvement on a previous version of this that uses 5mm white LEDs:

Nasty spotlighting in a previous version of the 2019 build, will be re-made with LED panel...

This is the business side of things:

Apart form the modifications described above, it's exactly the same setup as last season's box: Raspberry pi ZeroW (wifi), 8 MPixel v2 IR camera, IR-cut module. 5mm IR LEDs and White led panel (updated).  Illumination has high, medium and low (mood lighting) options.  Power is via 12v to 5v step-down. 

Video capture uses pikrellcam.  Video / image captures are stored locally, and can be archived off to a separate PC via wifi.  Local video storage overwrites if space drops under 20%.  This version uses the 'Lite' version of Raspian, so there is 13Gb available on the 16Gb micro SD card.  Based on last year's nesting activity that is good for approx 1 day of before a review is needed.  The prototyping board sitting on top of the Raspberry pi zero W is wired as described in this post (minus the rat-nest of wires for the LEDs...)

I wanted to add a microphone this year, but had real trouble getting a USB microphone adaptor working without noise interference.  The semicircular thing poking out the micro USB socket is a microphone, but its a fairly poor one.  I will probably not turn it on in practice... ironically a usb webcam I had spare gave flawless audio, but there was no way to fit it in and it seemed a bit silly to use an additional webcam as a microphone anyway...