sounds, sensors, stones
Compost isn’t something I’d even given much thought to, I got it in bags from B&Q and job done.
A long time ago I never bothered and used garden soil, perhaps an instinctive predilection towards natural farming – as exemplified in shumei.
At school I learned that soil has micro-orgnaisms that somehow worked symbiotically with the plants, but pretty much everything in the decades that passed seemed to run counter to that – perhaps my schoolbooks were from an earlier era.
In the UK air temperature is normally measured in a passively cooled Stevenson screen. The louvred design of the screen allows air to flow around the thermometer. The trouble with a polytunnel is there is no wind at all, as a result the sun heats the sensor up and without airflow you don’t know by how much.
By running a computer fan driven off a solar panel I can move enough air past the sensor to exchange the heated air from the sun shining on the sensor. For the sensor I use the standard Chinese supplied DS18B20 encapsulated in a stainless steel tube
The sensor is housed in a 6cm piece of white plastic waste pipe
The fan is mounted at the top of the pipe, designed to pull in air from below; this way the sensor is not heated by air passing the fan motor, and the airflow works with the natural tendency of warm air to rise. I’ve tried to keep the airflow as unimpeded as possible.
Looking at the results there is a difference of a few degrees
between the aspirated sensor and another sensor mounted on the outside of the plastic tube. They track at low temperatures but not when the sun is shining – the difference here is about 6 degrees, even in March, before the vernal equinox. It is remarkable just how much the air temperature swings – 27 degrees on a couple of days which still have hazy sun.
Weatherproofing the sensor is easier in a polytunnel because as well as the wind not blowing, it also doesn’t rain. I can use a cheaper indoor solar panel, the one I used is a 12V 1.5W unit, Maplin L58BF bought on sale for about £6, not the £20 they seem to be charging for it. even £6 is a little dear! I extracted the flashing blue LED and series diode to maximise the power available to the motor. This also charges the battery of the temperature sensor dual unit, which reports back to the collecting station using Ciseco’s XRF every 10 minutes.
The computer fan was a 12V brushless unit but I run it at about 7V, we’re not after blowing a gale through the tube. It will start at 5V. The Zener is there to limit overcharging of the 4.8V NiMH battery pack in the electronics to about 4mA. It only reports every 10mins so this is enough. The 1N4148 diode stops the battery discharging back through the fan and solar panel in the night. I should really measure what the leakage current of that Zener is 😉
I used a PIC 16F628A driving a Ciseco XRF to send the temperature data from two sensors back. Nowadays I would use the Ciseco RFu which includes an Arduino and low-power standby mods to make this cheaper.
This is a nice weatherproof design – I can’t work out if I missed a trick with using just one plastic tube rather than a coaxial design. Lots more ideas here.
This rig works reasonably well; if power were available I’d run the fan all the time in daylight for a more rigorous result on summer cloudy days. The biggest problem in a polytunnel is that they are shockingly dusty places, and you have to sponge the dust of off the solar panel every month or so.
Nowhere in the datasheet does Texas tell you “hey use this fixed regulator as an adjustable”. However, I’m used to being being able to do that with the venerable 78XX series – indeed Texas tell you that you can do that with the 78L05 datasheet in Fig 14.
Given that there’s an adjustable variant of the LP2950 that appears on the same datasheet (the LP2951) I laid out a PCB and being the lazy sort I am I assumed that since I was using a load of these parts in their 3.3V KY5033 variant, where I wanted an 8V stabilised voltage for an audio mic amp sourced off a 12V supply I can simply do the LM317 trick, drop in a couple of resistors from the output to ground and the ground pin to real ground, job done.
For this I made R1 6k8 and R2 10k.I expected an output voltage of 3.3+3.3/6800*10,000=8.2V or near enough. I screwed up labelling the o/p 10V, mistakes happen…
What does that look like then?
Oy vey, about 4V of massive oscillation (I’m using 10x probes). At least it’s centred on the right value-ish. Let’s take that output capacitor out
Looking good, only 1V of oscillation, now at 370kHz or thereabouts.
So if you come here from Google wanting to know why the LP2950 doesn’t work as an adjustable reg, now you know. There is a tiny clue in the datasheet in the ground current variation
which varies by two orders of magnitude with a load current variation of 1000. This will be impressed upon R2, varying the target voltage – as more current charges the capacitor the target voltage will rise, then ease off as it is charged, making a handy relaxation oscillator.
There’s another clue that the output cap can give interesting results in this line
which actually specifies a ESR range, rather than less is better
No criticism of Texas’ product implied – these are great little fixed voltage regs with a low quiescent current and are my goto device for running 3.3V devices off a 5V rail because of that superb dropout voltage of 600mV max, across the entire range of load current and -40 to 125°C which is easily in spec off a 4.75V min 78L05. It’s just one less thing to worry about. Im future I won’t be a doofus and try and use one where a LM317L is called for 😉
I love curlews – they may be common as muck round these parts but the beautiful plumage, strange down curved bill and haunting bubbling call make them special.
The little nature reserve at Melton has a free car park and you can get a view of the riverside mudflats near Wilford Bridge
It’s a pleasant walk along the river into Woodbridge, there is another small level crossing to get into the town. On the other side to Wilford Bridge going north there is a footpath toward Broweswell reedbeds and it’s worth a look at the birds on the riverside there too
SWT reserve Trimley Marshes is a long walk from the car park – about 2 miles to the hides. That’s good because it means you can sometimes have the place to yourself 🙂 On a bright winter day like today it is the Suffolk coast at it’s best, despite the surreal juxtaposition of the low rumbling sounds of the container port with the calls of the birds. The noise of the container port fades with distance. The port is behind you when looking at the birds, the sound wasn’t obtrusive from the second hide onwards.
I was treated to some lovely views of winter ducks – teal, wigeon, shelduck, and it was good to see a decent size flock of Lapwing.
recording of teal and wigeon – the wigeon are the whisting sounds and the teal are the regular metallic sounds
Closer to me was a male Stonechat and his mate, while in the hedgerows on the way out a flock of bum-barrels skitted across. Continue reading “Trimley Marshes Nature Reserve”
note – this is a Mk 1 version of the Canon EF 100-400 L
A working photographer uses their lenses all the time and probably never runs into this. I was into bird photography for a while, about eight years ago, and had the Canon EF100-400 IS L like every other wannabe bird photographer. In between now and then the field has separated the sheep from the goats – real bird photographers use longer primes, because the birds are always at the long end of any zoom. Or they use astro scopes on manual focus 😉
Anyway, I take time out from birds and photography, because life gets in the way, and I stow the lenses in a relatively cold room. A couple of years back I figured I’d take some long lens pics, and get greeted by this
which makes me curse. Mainly on the front element, though a starting spot on the inner element, which is part of the IS mech. The inner part is magnified by the biconvex front element. The spotty crap is on the inside of the front element, the fine filigree round the edge on the front of the front element. Continue reading “Canon EF 100-400 L lens fungus attack”
The idea is simple enough – a bird feeder camera on the network, using the Pi and associated camera. Using motion detection software I can pick out the birds. Of course I will also get the feeders swinging in the wind 😉
Although this is about running motion I can use videolan instead to stream the video as a netcam and use motion on a second machine. Videolan streaming
cvlc v4l2:///dev/video0 --v4l2-width 640 --v4l2-height 480 v4l2-chroma h264 --sout '#standard{access=http,mux=ts,dst=0.0.0.0:8082}'
is nice on the Pi, because it seems the camera can do the h264 in some sort of hardware/accelerated mode in the V4l driver. I can then watch the birds with realtime update rates on my LAN. That’s for another day…
Up to about mid 2014 it used to be a load of hurt to run Motion and the Raspberry Pi camera because there were no videoforlinux drivers for the camera. That way you don’t get a /dev/video0 for the Pi Camera and needed workarounds for Motion.
Now there is a driver which you’ll already have on a Raspbian install, and it’s easy to use. right out of the box. Continue reading “Raspberry Pi Camera and Motion out of the box – Sparrowcam”
Tucked away off the A1101 it’s easy to overshoot the turnoff because the bend of the road means the sign isn’t visible till you are nearly on the turn – even knowing that it caught me out. The low winter light was a treat on the leafless trees, painting them this lovely golden colour.
A lot of the water was still ice-bound, with a few channels of open water. All over the sailing club lake there was a marvellous ringing sound of teal. Not worth recording however since it sounded like the RAF were warming up their afterburners at RAF Honington.
The island only seemed to hold about twenty teal but their calls rang out over the water sounding like many more. I had the reserve largely to myself, with only a couple of photographers with hardy camo gear in the morning.
Monday seems to be the quietest day – the visitor centre wasn’t open though Suffolk Wildlife Trust did leave access to the toilets which is a kindness 😉 The small birds were staking out territories in the hazel coppice which was alive with the sound of competing great tits, which seem early to me – they haven’t started seriously marking out territory nearer home.
January has been quite sunny and mild this year so I visited the snowdrop walks in Walsingham abbey gardens. It was turning colder for the first day of the snowdrop walks
but it was a decent show for the end of January!
This is a description of how to make a remote farm camera. Smallholders don’t always live on site, or you may have an island site somewhere without power. The simplest solution to get pictures from a remote site without power is to use a 3G trail camera and these work very well for tracking wildlife.
The trouble with this solution on a farm is that animals are meant to be on a farm all the time, Trail cameras look for warm-blooded critters so mammals and birds will set it off all the time, making this an expensive operation in MMS messages, which seems to be the preferred method. Even if you get a MMS bundle, trawling through the false alarms will bore you.
was to be able to check on how things were going, and whether something has been damaged by stormy weather. A CCTV camera on the farm would be fine, but the problem with this is the power drain, and getting the pictures back. If we had mains power this would be a lot easier, we could use a 3G CCTV DVR with remote access capability. You can easily get 12V CCTV gear, but the power drain of a typical DVR and camera is quite harsh – typically 1A or more. A typical leisure battery is 80Ah, but you should only use half of the capacity of a lead-acid battery that to avoid reducing the service life of the battery, and you must never fully discharge it. This gives you a battery life of less than two days.
Our remote farm camera uses a Raspberry Pi Model A and associated camera to take a picture every 15 minutes in the daytime and upload it to a website
Continue reading “Oxford Real Farming Conference 2015 – making a remote farm camera”
