The sounds of summer at Bawdsey in the school holidays – a motorboat starts up and moves off, and then the passenger ferry arrives from Felixstowe Ferry
Bawdsey Beach
Bawdsey Quay
Author: richard
Wildlife camera with Raspberry Pi, Motion, and temperature sensing
I’m toying with the idea of going along to the Ipswich Raspberry Jam on Saturday 8th Aug and figure it’s be nice to have something to show. There’s of course our farm Raspberry Pi cameras which are in service and this one is riffing a bit off an idea Wildlife Gadget Man is playing with. He’s the guy with the wildlife – I only have sparrows[ref]I like my sparrows but they aren’t going to pose long enough for the camera, and presumably they have their heads under their wings in a hedge somewhere now, a hedgehog in a hog box is the sort of target that would work well here[/ref] so I have to make do with a stuffed toy stoat 🙂
There’s nothing earth-shatteringly new in here, but the ability to make a box which gives you video, snapshots and a temperature plot taken from one of those Chinese waterproof DB18B20 probes is good for mammals.
Continue reading “Wildlife camera with Raspberry Pi, Motion, and temperature sensing”
Brightlingsea
A couple of jetskis in the distance and lots of people enjoying the summer sun
Sounds of our Shores – summer 2015
Great project from the British Library to make a coastal soundmap. I took the opportunity to get under Clacton pier to record this
Lettuce timelapse
We tried growing lettuce seeds in compost 150527 and regular commercial compost. Right from the off you can see that out compost has a much coarser consistency, which is not ideal in seed compost
We then tried a timelapse view of some lettuce seeds growing, using a Raspberry Pi to shoot one image a day
This isn’t night and day, but I do feel the seeds grown in our compost are slightly less leggy than the commercial compost, but both are perfectly decent growing media.
Lettuce seeds are terribly small and fine, nothing can be said about the clustering or evenness,
Seed saving beans
The Seed Saver’s handbook says beans are easy to save, so it seems a good idea to start out with them, in this case some Sutton Dwarf beans. The idea if you leave them to dry in the pods and then save the good ones. Beans are an easy win as they adapt over the generations to the local conditions; they don’t use insects for pollination and the book says the gene pool is kept wide to allow self-pollination.
Right off the bat the book says that
The first pods to form are the best for seeds. They are to be found at the base and are larger than subsequent pods, Allow these pods to dry on the bush, and choose those from the most vigorous plants. Such refined steps cannot be taken on a large scale where a whole field is combine-harvested and threshed.
Well, we don’t have a problem picking seeds out of the combine harvester we don’t use 😉
The guys that wrote that book are Australian, and I guess they don’t have a problem with saying you need to store seeds at a relative humidity of 5%.
So I am writing on the evening of what has been a reasonably warm sunny day and I see the RH starting to skyrocket to 50% by 10pm and realise that I need to close the door to the conservatory because the dew comes in the evening as the sun goes down, not in the morning. 5% is going to be a tough call in the UK, probably involving silica gel. Interestingly the Seed Saver’s Handbook says good airflow is more important that high temperature, and it should not go beyond 35C anyway.
They’re right about those lower pods – long beans are definitely the place to go for the size of the seeds. You have to be pretty discriminating about the seeds, however.
Using near IR to look for photosynthesis and plant health with NDVI
The NoIR Raspberry Pi camera comes with a blue filter to do near infrared photography – the blue filter ices the visible red but passes near IR which records as red, apparently.
NDVI (Normalized Difference Vegetation Index) is the near IR plus red divided by near IR minus red. Take a look at this image for the meaning of the colours – red, magenta and white is more photosynthesis, cool colours and black are less. Chlorophyll uses red but doesn’t use near IR which it reflects, hence the difference carries useful information.Lots more at Public Lab. Continue reading “Using near IR to look for photosynthesis and plant health with NDVI”
Measuring paramagnetism 2 – a new sensor
Since I will be taking the sensor to the rock I’m going to temporarily give up on getting an absolute measurement, and take a leaf out of Bartington’s book from last time and use a flat coil. I will never be able to contain the sample in the magnetic field1 as I might be able to in a solenoid, to the effective susceptibility will always be lower than 1. One day I may be able to calibrate this and find a fixing factor, but for now I will look for relative differences.
Measuring paramagnetism
There are two approaches to measuring paramagnetism that seem to be common. One is to use a balance to measure the slight attraction to a magnet – put sample in a balance, apply magnetic field, look for difference in weight of sample using a Gouy balance or use a torsion balance to observe the attraction in a horizontal plane which takes out the static weight of the sample.
The trouble with these two is the attraction due to paramagnetism is weak compared to the weight of the sample – these are lab bench instruments and the electromagnet consumes a lot of power. Although taking samples of soil is easy enough to bring back to the lab, one really shouldn’t be taking a hammer and chisel to ancient monuments to get a sample for a Gouy balance 😉
The other way of measuring volume magnetic susceptibility is to stick the sample into a coil and measure the inductance – with a different configuration of the coil as a search coil it can be used to measure susceptibility at the rockface.
Paramagnetic soil ponderings and perambulations
Paramagnetism is a reasonably straightforward characteristic of materials – if there are unpaired electrons in the atoms then the element will be paramagnetic and weakly drawn to a magnet. This demo of oxygen being paramagnetic is great – so far so scientific. Compounds can change this – water is diamagnetic although H2O is clearly contains oxygen.
When applied to soil and the growth of plants, however, paramagnetic effects fall into the domain of the woo-woo rather than the analytic 🙂 Igneous rock and volcanic soils tend to be notably paramagnetic. Philip Callahan is the go-to source, and this extract from a 1995 Acres USA article is a high-level spin on his take : Continue reading “Paramagnetic soil ponderings and perambulations”