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Solar Powered 12V lighting system

This project is about resilience more than energy saving, though it can also be used to save energy. Total costs should be in the order of £100, but there are ways to reduce that by getting some items from Ebay. The idea for the project came from the Transition Ipswich Energy group in 2011. It had to be targeted at a competent DIYer, and is for small scale lighting. This was originally published on TI’s website, which is no more.

This project lets you run lighting off of solar power, effectively storing sunlight for later use. It can be used at home to keep lighting during power cuts, but the same principle can be used to provide power to sheds on allotments, outbuildings or island sites without mains power. Although I have used lighting as an application, such a system can run an electric fence for much of the year if suitable solar panels and battery are used.

The system as described lets you run one or two 12V 1.8W LED lights through the year – my system was able to run mine through the winter and the shortest day where the light would be on from about 6pm to 11pm. In the summer you can also run a laptop computer power supply independently of the main for a couple of hours (these run typically 40W). That is because in the summer you get far more solar energy and you’ll probably use the lighting less.

If you want to primarily save energy or reduce your carbon footprint using solar power, this is not the solution. For that it is best to get a grid-connected solar power installation which will allow you to save energy and get renewable feed-in tariff payments. That sort of thing is on a different scale from this project, and capital costs are usually in the order of several thousand pounds, but the energy savings are much, much greater. A grid-connected solar PV system does not give you resilience against power cuts, because the anti-islanding systems in the grid tie inverter shut the system down if the main power fails, so that a PV system does not send power back into the grid when it may harm power workers trying to repair faults.

Continue reading “Solar Powered 12V lighting system”

Soundman OKMII repair

I’ve had my Soundman OKMII binaural microphones for over ten years, and they are my favourite mics for urban field recordings. DACS is the UK supplier.

They don’t really work in wind, and they aren’t the quietest, but they are as stealthy as you can get, looking just like earbuds. A decade ago you still looked a little bit of a geek using them and monitoring on a recorder, but nowadays most people are looking at their smartphones, rather than the lamp-post/road they are about to encounter. On the off-chance that they do look up, they will assume you are just another human trying to escape the real world for the virtual one inside your phone, which happens to be a field recorder.

I was going for a general recce on the Somerset levels, looking for interesting sounds. I heard a lot of birds congregating in some trees, and started the OKMII. There was a lovely little flurry of about 100 starlings flying overhead at about 2 and 4 secs against a background of other starlings gathering in the trees

The OKMII isn’t really a birding mic, but it picked up some of the essence of these guys

and then I encountered this ghastly full-scale 0dBFS noise on the left

a bad contact on the left channel. After 10 years these mics don’t owe me anything, but I figured it’s worth a look if a fix is possible. Skinning the foam earpads shows this

OKMII Two plastic shells melted together

It’s possible to separate these with a craft knife along the obvious seam, concentrating on the melted bits. The microphone is glued to the shell with a hole, try and keep this together to expose the contacts on the rear of the capsule. Continue reading “Soundman OKMII repair”

Raspberry Pi camera after several years outside

It doesn’t pay to put a Raspberry Pi camera out directly facing the great British outdoors for more than a season even if you can keep the water out of it. I had a RPi Model B and camera doing just that and groused about the lens crazing problem where there seems to be some sort of microbial attack on the lens after a season outdoors.

you can just about see the grungy effect on this damaged Raspberry Pi lens which was outdoors for a season. The mechanical marks around the outside is because you have to break the glue to get the lens out. I did not mechanically damage the lens.

That didn’t respond to pretty aggressive scrubbing with isopropyl alcohol (IPA), and the Pi lenses are proprietary.

The back side of the lens not facing the elements looks fine

They are not standard M12 CCTV lenses¹, so I got to buy another camera board, and used Sugru and a cut down glass microscope slide to try and keep it intact. I can buy aftermarket RPi compatible cameras using M12 CCTV lenses now, but then it wouldn’t fit in the PICE case.

Pi camera behind glass — The Pi camera is still bright-eyed after three years in the outside, behind a glass microscope slide

I left this camera out in the open on the farm for a while, and then watching my sparrows on the feeder. It looks like the glass slide technique has been a win, it’s been around three full years and the camera lens is still OK. The slide can be cleaned with IPA and comes good as new. Angling it down slightly reduces reflections and flare, but yes, it is uncoated so flare will happen. I built the Sugru up a but round the top to make a lens hood to minimse the amount of open sky that falls on the glass. Maybe the original Pi camera lens is plastic and gets eaten, although I know to my cost that optical coatings on glass can get hit by fungus too in damp conditions 🙁 Continue reading “Raspberry Pi camera after several years outside”

Wolf Supermoon

The first day of the New Year features a full wolf supermoon, ¹ when the Moon is closest to the earth so brighter and bigger. The Moon was lovely so I figured I’d try for a shot. the Independent tells you why it’s a Wolf moon.

The Moon disc itself is as bright as the beach on a summer’s day when you are taking a picture of it, because it’s in full sunlight, no clouds and about the same distance from the sun as the Earth. Should be a doddle – I got the Canon EF 100-400 lens that I cleaned up, put it on a monopod and aimed at the Moon. f/8 1/400 ISO200 go.

Turns out not to be as easy as that. I needed a tripod, switched off IS and even then not every shot was equally sharp, must find the remote cable for the Canon, maybe it’s mirror slap. Took the best, that’s the top picture. I then tried my Micro Four Thirds camera with a 100-300 lens – the MFT sensor is probably smaller than the APS-C sensor on my EOD450D so the 300 end is probably comparable with the 400 on the Canon Continue reading “Wolf Supermoon”

Storm Ophelia

Wind is normally the enemy of sound recordists, but going through some recordings from last year I found this recording of ex-hurricane Ophelia from the 16th October 2017. Ophelia had been pretty nasty originally and was still bad when it got to Ireland.

I recorded it in Glastonbury in the south-west, by finding a sheltered spot and pointing the mic in a windshield at a bunch of trees, which made a good recording given the wind. The key was that I had good shelter at the mic, but the trees were exposed to the full force of the wind.

The storm dragged up a load of Saharan dust, making the sky the sickly yellow in the pic.

Experiences with the Vilistus EEG interface

I went to an open day in October run by the mind people, makers of the Vilistus EEG interface. It was an opportunity to see this in action and ask questions – the day was £85 which wasn’t too bad, there were about five other people there. It was run in some anonymous hotel near a football ground in Birmingham just off the M6, and led by Stephen Clark who knew the product well.

It was an interesting day, the Vilistus 4 box is a digitising interface but analogue signal conditioning is done in the sensor boxes, which add some cost to the overall system. Their default software looks fine even for Mind Mirror since it seems to have the filter bank in it, the extra costs for the Mind mirror package probably involves extra training. You seem to get the vilistus pro software with the box. I haven’t seen any of the units come up on Ebay.

I learned that the interface between the Vilistus interface and the computer is OpenEEG P3, which was good to know, and Stephen did warn that a lot of the older OpenEEG code from the OpenEEG project made the assumption that there were only 6 active slots rather than following the protocol specification which allowed the source to say whether there are 6 or 8 slots of data. Vilistus use 8 slots, so code assuming 6 would barf.

He did say the existing API would allow the Vilistus Pro software to continually dump the values of the filter slots to a text file that could be read by a program to display the output on LEDs, obviously I would get to build the interface and write the program 😉

The Vilistus Pro software did show correlations well – most clearly on a display where they showed heart rate against a trigger for breathing in and out. The heart rate slows a teeny bit on breathing out relative to breathing in, although this effect fades with age – it was clear on the 25 year old student and not really visible on a 50-something lady on the course. EEG was tough to get going in the course, although it was demonstrated using disposable electrodes on the forehead. This isn’t the optimal placement for Mind mirror but you can’t use disposable electrodes on areas of the scalp covered by hair.

The trouble is this rig would be about £1200 all in, and I’m not yet sure I am £1200 interested in the Mind Mirror. I did get a much better feel for using this in the field, and I’m aware that while I have been able to solve the digitising side of things using the PIC, I still need to solve the EEG diff amp, and solve the electrode problem.

Vilistus seem to have solved a lot of that, but even the electrode set is ~£200, so the bundle would be the way to go. One to mull over really, to work out whether I want the functionality or the engineering challenge. I could probably knock off £500 going DIY if the development went OK, but experience shows only one to two PCB fails or wrong turns can wipe out the savings on a one-off project where there’s a COTS solution.

One to think about. The Olimex EEG-SMT and 4 electrodes is about Euro100 – okay so it has the iffy antialiasing filter but a £1100 saving has its attractions 😉

Making compost tea

We are using 160901 to make compost tea. Although the temperature has fallen to ambient, it’s still a bit early. This is only seven weeks old, and it’s apparent that while all the green material and plant material has gone and isn’t recognisable for what it is, the woodchip takes longer to break down. As such it will be mainly bacterial, the fungi take longer to develop. Fungi are better at decomposing woody material. But sometimes it is not worth letting the perfect be the enemy of the good.

Looking back at the success we had with the beans there is some latency of a few months between putting the compost organisms out, compared with the more modest results after only a couple of months, so we want to get this out now to do its work over the winter. Continue reading “Making compost tea”

Fonnereau Way Soundscape

The Fonnereau Way has been used since the mid-1800s, although it’s been the subject of a fight when a incoming resident at the Westerfield end tried to block it up and have it stopped on several occasions. Network Rail has also had it in for the pedestrian level crossing but have also failed to have it struck off.

The path is slated to become a feature in the new Ipswich Garden Suburb development and the level crossing will be replaced with a bridge according to this document.

The Fonnereau Way is the mainly vertical line to the left, with a bridge to put ‘elf’n’safety at Network Rail out of its misery

Becoming a housing estate will clearly change this part of the Fonnereau Way, so I walked this to capture some pictures and soon to be historical sounds from the route. The farmland is intensively farmed and heavily sprayed as I’ve observed a few times, it’s quite possible that being turned into a housing estate may actually increase the biodiversity. Although the birds will be persecuted by hundreds of domestic cats and the gardens will no doubt be tiny, the farmland doesn’t support that many birds at the moment.

The Fonnereau Way starts from Christchurch Park, but I started where the changes will be made, where it crosses Valley Road. In the local plan all vehicle access will be from Henley Road rather than Valley Road.

the nondescript entrance to the Fonnereau Way from Valley Road

and it’s a noisy place. It gets better quickly as the old path threads its way past some sports facilities and the playing fields

before reaching farmland

The path breaks out of the hedgerows on either side and starts to cross farmland

There are a few birds in the farmland, but to be honest the urban Brunswick Road Rec has more diversity to my ears, the birds are few and far between

A chiffchaff makes itself known.

Oscilloscope options – standalone or PC based?

I started redecorating the lab, so the EEG project is now relegated to an Autumn/winter project 😉 Which is a shame as I’d got close to replicating the Mind Mirror system in Open EEG and getting a hardware gizmo set up using a PIC. The best laid plans of mice and men…

Just before I cleared it down I tested a device I’d been given by Jason Wildlife Gadgetman when he was clearing his lab out getting ready to move. The DrDAQ is a bare-board device made by Pico Technology. which shows a lot of promise for the openEEG testing.

It’s basically a single channel digital oscilloscope, but it works with Picotech’s Picoscope software, which has all sorts of features that are new to me, like software RS232 decoding, click to set trigger levels, and long persistence simulation.

I have a decent Tek 2245A analogue scope, which computes frequency and voltage levels from cursors on the traces,

This is now very old , from 1989. It does most of what I want/need, and most of my design career I worked with analogue ‘scopes, with the logic analyser as a separate piece of gear. However, despite its measly 100kHz bandwidth the Pico did show me some of the attraction of a more modern approach. Every so often I’ve toyed with the idea of getting a Chinese scope, something like Rigol 2000 series or similar. So far I haven’t cracked. There’s a lot to be said for a standalone scope, but I wonder if the combination of my regular analogue bench scope together with a Pico will be even better.

EEVblog did take the piss out of the cheap Chinese DSOQuad FPGA scope, and I’d agree with him. I got one of these DSO Quads to be able to print out slow captures like the one in this project, and it works well enough at that

but it would be a terrible thing to do to give this to a beginner. I could only make this thing trigger properly because I’ve used analogue scopes for years and had some feel for what should happen – all too often on the FPGA scope if the vertical trigger wasn’t in range you simply don’t get to see anything useful at all, so you can’t see which way to shift the trigger point. And the user interface is revolting. Too much clickety-click of two separate left-centre-push-right buttons for my liking.

Picoscope is far better thought out although it still suffers from the problems of not enough control of input sensitivity and offset as a regular bench scope. But it, and the associated DC coupled arbitrary waveform generator will be a great tool for testing the OpenEEG filters at sub-audio frequencies. And unlike the typical fly-by-night USB scopes, the software supports legacy models back to when Pico started, because that is of course always the problem with any hardware that depends on a piece of software running on some other device – it easily becomes orphaned before its service life is over. See pretty much any hardware made by Apple that is more than three or four years old 😉

The DrDAQ does pretty much all that I want for the EEG work, but the AWG doesn’t support frequency sweep mode which is a shame. I’d need to go for something like the 2206B at £250 to get that. In that case I’ll probably do it the old way and set up the AWG to output a single frequency and step through the frequency range. What isn’t clear is the frequency resolution of the AWG.

Thorpeness boats

The Meare at Thorpeness is only three feet deep and even a light breeze seems to rock these boats making a lot of noise.

A nice place in the summer – not so rammed with people as nearby Aldeburgh can be, and the boating lake is fun. Easy reach of the beach, too. The lake gets a good view of the whimsical House in the Clouds water tower

The Peter Pan-themed lake and the House in the Clouds are the creation of Scottish barrister Glencairn Stuart Ogilvie at the start of the 1900s