A lower energy more expandable Pigcam network

Is covering a 12-acre farm with WiFi a reasonable idea? If so, I could run multiple cameras, say have one on the cows and one on the pigs, all connected to a central location, On the upside, the farm is roughly square and with a mild slope to the ridge at the top. Everything is pretty much line of sight. On the downside, there’s no good central location, which would be the obvious way to service the farm with 2.4GHz WiFi. Distances are long – the field is about 250m wide/long, and I could easily pick up a 300m path length feeding from the edge.

the MiFi node and power management
the MiFi node and power management

Earlier experiments showed that I could in theory use native WiFi, using a router to receive BTFon from a broadband connection in the town over a high-gain antenna and redistributing it from a WiFi AP. The trouble is I am desperately short of power – every extra piece of kit means more frequent battery changing. In the end I went with a more powerful MiFi access point – one that supported an external WiFi aerial. I used a 9dB TP-Link patch antenna

This feed the farm from one edge, as it happens the antenna is furthest away from the most likely camera sites but slightly higher than the target sites. The signal pattern fans out quite well, serving the likely points of interest. I was chuffed with the performance of the aerial – it gives the right balance of directionality, as I don’t need to bother to serve the field behind me, but it gives very useful gain in the wanted direction – I can just about get a wifi connection with the internal antenna of my iPod touch from the opposite corner of the field. As the forest garden and some of the windbreak trees grow I may experience problems, but that is for another day. By then perhaps we have a site with mains power 🙂

For the MiFi unit I used a TP-Link MR3220 – it’s surprisingly hard to find a MiFi box with an external WiFi aerial socket, because not unreasonably they anticipate you using this sort of thing as a personal cloud. I had to live with the 9V powering and used a Chinese Ebay 12V to 9V converter switchmode converter to efficiently turn the 12V battery power to 9VDC

The other part of improving range is to upgrade the camera end with a WiFi card with an external rather than internal antenna; since the Pice case has been withdrawn I need another solution for that. The PICE case also still exposes the Raspberry Pi camera lens to the elements which is Not a Good Thing leading to the lens haziness problem.

It doesn’t really matter how big the camera is, so I took the opportunity of using a much larger box – a  Hammond case 1599 to fit it all in.

If you’re going to put something outside then the fewer holes you can drill the better, hence the use of sticky pads and cable ties as mounts, and the single 2.1mm power socket on the base, so water could drain out that way if necessary, and could be standing 0.5cm without affecting the electronics.

The case has several mounting lugs in the lid, but in the end I will have to drill a hole for the camera. I placed an O ring on the case and a microscope slide pressed down by foam and the camera to make a watertight seal but keep the elements out of the lens; that way hopefully I get to either clean or replace the microscope slide after a season is out rather than the camera.

camera mounted in the lid
camera mounted in the lid. Reed switch is top left wit the yellow wires, the 1p glued to the case holds the magnet there because they are made of steel these days not copper.

The 12V to 5V converter is mounted in the case; that way any cable losses aren’t too bad and the current in the supply cable is reduced, it is about 200mA max.

Setting it up in the field

Pig Camera in service
Pig Camera in service

The paving slab is there because the first version of the tripod ended up flat on its back in the morning. At least the construction can survive a fall of 2m. Perhaps the neoprene sunshade and the extra area at the top of the pole presents too much wind loading.

Camera close-up
Camera close-up

Controlling the Pi

I postulated all sorts of complex feedback when first considering this, letting the Pi tell the microcontroller to turn the Pi off with a GPIO pin, but it’s been massively simplified. A microcontroller powers up the Pi, and pulls the power after 5 minutes. Then it waits 10 minutes and does it again, provided that the 12V supply is enough (>11.5V) and it is daylight.

I use similar Python code to the first cut, but this time I start running the takepic.py camera code on startup. I look for a switch closed on the GPIO, and if so, abort uploading the picture because the Pi is in service mode1. This switch is a reed switch mounted on the inside of the case and activated by sticking a magnet to it, this saves a hole. It lets me get onto the Pi and configure it. Normally the switch is open, in which case the Pi tells the system to do a shutdown in 4 minutes, which is enough to connect, get Wifi network DHCP and SFTP the picture to the website. 5 minutes after powerup, the microcontroller managing power pulls the power from the Pi.

The shutdown command on the Pi minimizes the chance of corrupting the SD card, and the picture is written to the /run/shm/ ramdisk prior to uploading, since there is no point using up SD card write cycles with ephemeral data like that.

#$Id: takepic.py 58 2014-11-06 20:54:02Z ermine $
import time
import picamera
import paramiko
import os
import socket
import datetime
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BOARD) # USE Pi BOARD pins, not the BCM ver
GPIO.setup(7, GPIO.IN, pull_up_down=GPIO.PUD_UP) # 7 is next to gnd on pin 9, so set pull up

# defs
remotename='WEBSITE.COM' # assuming this is reachable by ssh and www
try :
    with picamera.PiCamera() as camera:
        #camera.resolution = (2592, 1944)
        # The following is equivalent
        #camera.resolution = camera.MAX_IMAGE_RESOLUTION
        # run half res to test out connectivity etc and save money
        #camera.led = False
        camera.resolution = camera.MAX_IMAGE_RESOLUTION
        #camera.resolution = (1296, 972) # do half real to eliminate Bayer softness and save TX bandwidth
        camera.capture(DIR+imagename, resize=(1296,972), format='jpeg', quality=20)
except picamera.PiCameraError,e :
    print e
finally :
time.sleep(10) # hopefully nw is up by now 
if(GPIO.input(7) ==1):
    #print "will shutdown"
    os.system("/usr/bin/sudo /sbin/shutdown -h +4 &")

    if not(camerafail) :


        while (not timedout) and not connected :
            try :
                s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
            except socket.error,e :
                counter += 1
                print counter
            if counter >= 5:
                print 'Failed to connect to ',remotename,' ',datetime.datetime.now().strftime("%y/%m/%d %H:%M")

        if not timedout: 
            print 'ftp image starting ',datetime.datetime.now().strftime("%y/%m/%d %H:%M")
            try :
                ssh = paramiko.SSHClient()
                ssh.connect(remotename, port=2222, username='USERNAME', password='PASSWORD')
                sftp = ssh.open_sftp();
                sftp.put(DIR+imagename, '/home/DIR/'+imagename)
                print "closed SFTP"
            except paramiko.AuthenticationException,e :
                print e
            except socket.error,e :
                print e
else :
    print "manually aborted by jumper 7 to 9"

Power savings

This has massively reduced the power drain of the camera – it is < 200mA for a third of the time, with an outage during the night of about 1/3 of the time, so about 1/3 × 2/3 × 200mA average, ie ~50mA. The original power drain was about 300mA 24×7.This power drain is much less than an electric fence which is usually about 150mA, so it could be used from the fence battery, which would then let us monitor the fence battery voltage as a bonus.

It also suits solar panel charging well, as the power drain is proportional to day length. The WiFi node draws more (a sustained 200mA during the day) but at least it is just one place where the battery needs changing more often – about once every two weeks. That’s livable with, but if I’d used a WiFi long-distance connect and a WiFi high power AP that would be shortened too much, particularly as logging into BT Fon would require another Pi to keep the connection open. GiffGaff run about £7.50 per Gb PAYG which isn’t bad.

Got pigs

Got pigs
Got pigs, end of the day picture in lowish light, 4:30 pm November

So far so good. The new pigcam

  • works all over the likely sites on the farm
  • concentrates the data through one GiffGaff SIM[ref]data service gets cheaper with volume, so this is much better than each camera having a SIM[/ref]
  • reduces power at camera sites to minimal
  • lets me add more than one camera to the system

which is a success compared to the single site version which had a very high power drain because it wasn’t being power-managed.

Pigs, photo taken with a regular camera earlier in the day

  1. In service mode I get to ssh into the Pi to configure it, and issue the shutdown command manually – I bypass the microcontroller shutdown for that 

a Raspberry Pi camera after a season outdoors in the British weather

The old pig camera is due for a rebuild. I went with the Pice outdoor case for the new one, but  it’s interesting to see how the old one stood up to the weather. It was still operating when I decommissioned it because I needed to scavenge some of the network parts for the new one. In particular I now use a central WiFi/Mobile node to cover the whole farm, and use Wifi to upload the pictures for each camera via that node.

The original one ran the Mifi node and the Pi all the time, which was hard on battery power. Hence the rebuild, but if the case held up over a season I may as well use it rather than splash out for a new Pice…. The original case was larger than it needed to be, but I can now use this space to put the light sensor and 12V to 5V DC-DC converter inside it.

So how did it stand up to the ravages of the elements. When it was new it looked like this

best not let the IEE see that else they'll revoke C.Eng for disgraceful and outrageous bodgery of the first order ;)

and the innards looked like this

the Pi gets big fast when you hang enough onto it to make it useful
the Pi gets big fast when you hang enough onto it to make it useful

So from the outside it now looks like this

Raspberry Pi camera after a year in the open
Raspberry Pi camera after a season in the open. The messy carving of the rain-shield started out that way

Which isn’t bad. It vindicates one of the things i did, which was to use plastic screws for mounting. Unfortunately the camera needed M2 screws which were steel, and these rusted. The sun bleached the tape, but the box itself stood up to the light well.

The cheap Chinese DIN socket is starting to rust


I had fitted this on the underneath of the case. There are two philosophies when it comes to trying to run electronics outside. One is to go IP65 all the way and keep water out, which means waterproof enclosures, Dri-Plugs for power etc – you’re looking at about £20 to get the power through the case and maybe another £20 for the case itself. Farm hacks don’t really need that sort of ruggedness, which brings me ot the other philosophy

Accept water is going to get in. Mount all connectors on the bottom so it can drain out. I actually picked this up from the PICE guys – they mount the raspberry Pi on the lid of the case, so water could be standing on the bottom half and it would be okay.

No evidence of water, no creepy-crawlies - great
No evidence of water, no creepy-crawlies – great

As it was no water seems to have penetrated, no creepy-crawlies seem to have got in. The latter are a pain with electronics outside- they seem to be attracted to the heat, or maybe the power itself. It certainly helps to lift the device into the air, or simply put it on a stick a metre or so high, compared with ground mounting. But this looks clean, there’s a little bit of evidence ingress on the seam, and the PVC tape degraded in the UV so this may be worth some thought.  I will re-use this box, mounting the microcontroller timer and the light sensor on a board set into the rails, so I don’t have to drill the box for mounting.

However, one thing has been impaired, and that is the lens of the camera, which gives a hazy effect – it was clear and not foggy when this picture was taken

Flare on the camera lens after a year in the open
Flare on the camera lens after a season in the open

Normally a CCTV camera is behind a piece of glass to keep the elements out and now i know why. Cleaning the lens with IPA didn’t help. I am tempted to glue a piece of microscope coverslide over the tiny lens in future this would have the optical quality and would be cleanable/replaceable. Continue reading “a Raspberry Pi camera after a season outdoors in the British weather”

PICE case and WiFi upgrade for the remote farm camera

The issues with the Raspberry Pi farm camera were of waterproofing and of iffy Wi-Fi range. Both of these are addressed in the new version. The PICE waterproof case from the guys at EdVenture marshals this motley collection of bits

Pre-PICE prototype
Pre-PICE prototype

into something a bit more organised. There’s no getting away from it, the PICE is quite expensive at about the same as the Pi itself, but it does solve a lot of the mechanical problems of trying to run a Pi outside with a camera. The landscape version is the one i needed, since the case is only water-resistant with the top horizontal – the Pi is mounted on that and even if water does get in it falls to the bottom away from the Pi. The previous version of the PICE took the picture in portrait mode with the case oriented for best water resistance, which isn’t so useful for our aims.

This is a good interim solution – it gets the cameras into a tighter configuration, and should let me pull back the main MiFi box back to a more central location to serve the rest of the cameras. As a result each camera will draw less power which is good. The Edimax EW7711 USB WiFi unit has a better performance than the USB nano-dongle – the reason is obvious when you look at the size of the aerial of the nano

size really does matter in some applications, and and aerial much less than 1/4 wavelength is going to struggle to get the signal out
size really does matter in some applications, and and aerial much less than 1/4 wavelength is going to struggle to get the signal out

although it’s 2.4GHz the wavelength is still 13cm; you still need to get enough metal in the sky to get the 300m path length to work, unless you can mesh. Continue reading “PICE case and WiFi upgrade for the remote farm camera”

Remote Farm camera – experimenting with WiFi

Clive from the Raspberry Pi Foundation very kindly let us have a Pi Model A and camera, so it’s time to take this project forward a stage. At the moment the alpha test version is in service keeping an eye on our new piglets. Although the original purpose was to keep an eye on our newly arrived cattle pigs are more enterprising, so it’s good to know where they are

Our camera on the pigs
Our camera on the pigs

Development was stalled however since it’s not easy to work on a piece of kit in service.  Ideally one MiFi box could serve a number of cameras. This would reduce the camera power drain and consolidate.

The trouble is that the site is on the edge of town, a couple of hundred metres from the nearest houses, and I want to use BT Wi-Fi

Yagi wifi antenna
Yagi wifi antenna

I acquired one of these from ebay I didn’t have much hope for the integrity of the device, and to gain height I needed to go 250m further way from any likely source of WiFi. But it worked a treat, as a WISP client, I’m amazed. I was able to see 18 access points, five of which were BT WiFi , 3 of which were 5dB or above. The TP-Link gives a decent link at more than 5 and nothing at 2. I streamed a video to confirm the stability of the link.

TP Link signal strength with yagi
TP Link signal strength with yagi

I use it with a TP-Link TL-WA5110G which has the advantage of having a sma antenna socket and a native power supply of 12V. Although the adaptor is specced at 1A I measured the power drain at about 210 mA (~2.5W @12V). Which isn’t great but not terrible

A WISP client is not a  repeater

The trouble with using the tP link as a WISP client is the signal is presented as Ethernet, and I’d then want to re-radiate the signal on a different Wi-Fi network.  I could set it as a repeater, but then every Raspberry Pi would have the hurt of logging into BT WiFi. Whereas if I use a Raspberry Pi connected via ethernet to the TP-link and a WiPi dongle to connect to the farm I can collect pictures from the cameras on the farm network and perhaps power-manage the TP Link to only update every so often.

So an unexpected win, and I can look at using a Model B as a concentrator