And in other news…

the hedgehogs are back in our garden:

Welcome back!

Welcome back!

This is a combination of the PiNoIR camera (v.1) along with this IR motion detector (the sensor is expensive because it’s digital), and some near-IR LEDs.  Below is a picture of the older model – the newer one runs on an A+ (for size and power reasons) and has been updated to Jessie, and now the LEDs are switchable by GPIO via a mosfet to provide lighting for the camera only when needed.  The upgrade to Jessie means she boots without WiFi at night, and the next morning, I can add the WiFi dongle to connect and check the results.




#!/usr/bin/env python
# NiteLite - a python daemon process started at system boot, and stopped on shutdown
#          - the default LED pattern is twinkling but if motion is detected, one of 4
#            different patterns are chosen and these are used for 10s after motion detection
# Please see our GitHub repository for more information:

import signal
import time
import RPi.GPIO as GPIO
import os
from datetime import datetime
import subprocess

# Set up the PIR movement detection

# Final steps of setup
keep_looping = True

def Daemonize():

# Once booted, give the user a couple of minutes to place the camera
time.sleep(2 * 60.0)

    while keep_looping:
        # Block waiting for motion detection
        GPIO.wait_for_edge(GPIO_PIR, GPIO.RISING)

        # Turn on the IR LED
        GPIO.output(GPIO_IR_LED, GPIO.HIGH)

        # Take a snap
	now =
	now_string = now.strftime("%y%m%d-%H%M%S")
	camera = subprocess.Popen(["raspistill", "-rot", "180", "-o", "/home/pi/Pictures/img_" + now_string + ".jpg", "-n", "-ISO", "800", "-ex", "night", "-ifx", "none"], preexec_fn =  Daemonize)

        # Turn off the IR LED after 5s
        GPIO.output(GPIO_IR_LED, GPIO.LOW)

        # Wait 30s before checking for motion again
except KeyboardInterrupt, e:


Save it as /home/pi/ and make it executable:

chmod 775 /home/pi/

Load on boot

Raspian uses systemd for running on boot.  In /etc/systemd/system, create a new file called hogcam.service:




Save it off.  You can then enable, start and stop it thus.  It will also start on boot.

sudo systemctl enable hogcam.service
sudo systemctl start hogcam.service
sudo systemctl stop hogcam.service




Another walk up the side of the house, but then walking a square as best I could, finishing where I started, and as you can see, the camera tracked this amazingly well – I’m particularly delighted the start and end points of the square are so close.  Units are pretty accurate too.

I’m now very keen for Hermione’s parts to arrive, as I suspect this is going to work like a dream, both stabilising long term hover, and also allowing accurate traced flight plans with horizontal movement.  Very, very excited!

Shame about the trip to DisneyLand Paris next week – I’m not going to get everything done before then, which means Disney is going to be more of a frustrating, annoying waste of my time than usual!

Better macro-block tracking

With a more careful test this morning, here’s what I got.

Video macro-block tracking

Video macro-block tracking

This is at least as good as the PX4FLOW, so that’s now shelved, and testing will continue with the Raspberry Pi Camera.  I upgraded the camera to the new version for this test, as that what I’ll be installing on Hermione.

The cross of the diagonal and vertical should have happened lower so that the diagnonals to the right of the vertical overlapped – these are the exit from and reentry to the house from the garden.  There are multiple possible reasons for this, and because this is now my code, I can play to resolve the offset; something I simply couldn’t do with PX4FLOW and its offsets.

Next step is to sort out the units, including which direction the camera X and Y are facing in comparison with how Hermione’s X and Y from the accelerometer and gyro are facing.

Drone Camera first shot

I’m taking a break from PID tuning today, as I need a rest.  Instead I had a little tinker with getting RaspiCam to work.  The drone is already flashed with the latest (June 2013?) image, and the wires connected so all I needed to do was to run raspi-config to enable the camera, and then do “raspistill -o test.jpg”.

All I got error messages suggesting I checked the wires.  The wires were good, but somehow I’d managed to detach the connector between the camera and it’s board – the little gold rectangular one – I didn’t even realize it was a connector, but there it was flapping around loose.  A gentle push reattached it, and it must have worked as another try with raspistill led to this – the box the drone was sitting on:

Drone camera first shot

Drone camera’s first shot

I’m already half way through the code which can spawn off raspivid, so once I’ve got the PIDs sorted, hopefully I’d be able to record videos too!

PiCam case

I’ve bought a PiCam case to protect the delicate cable and electronics the other day.  I fiddled and faffed to get the camera in safely and securely without damaging the cable or camera itself, and then finally realized that it was really simple and elegant once you know how.

There are two things you need to know: firstly there is some flexibility in the case; be gentle but it does bend; secondly, there are two slots in the back piece which the board clips into perfectly – this is the bit I missed at first.

Don’t faff like I did trying to ensure the camera poked through the hole in the front while attaching the back – that’s completely the wrong way round.  Instead, clip the board into the slots in the back, feeding the cable under the tiny slot in the base; once the board and cable are safely secured like this, just clip the front on and Bob’s your Mo’s Bro!