Nordintown Blog

Rubbish musings, projects and hackerings from Nordin

Trip Hazard

Nov 192016

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Taken during a lunchtime walk; Garthdee along the river path, sometime over August 2016

As I was out on another lunchtime health work along the River Dee, I tripped over a log. Post-recovery, I saw the log was in fact a rare metallic shrub flowering it's polished topside. Its hard to imagine that in just a few years, this small sturdy fixture - a relative of the common paper-clip weed - will be a mighty 12ft boat anchor.

Wall Moss

Nov 152016

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Taken during a lunchtime walk; Deeside, sometime over August 2016

I enjoy seeing things like this. On a wall, up a building, on a dead log - I tend to imagine a time-lapse version of it's progress with the Attenborough-esk fabricated 'plant' soundtrack of wet clicks and crackles.

Mosses are indicators of pollution and generally, they grow only in clean environments. This doesn't mean that the postcode the 'green thing' has found is free of man-made muck, but perhaps implies that a conscript of the local biome has judged the host object as something they can at least work with.

Solar PV results 6 months in ..

Sep 082016

The install consisted of 12 BenQ PM096B00 panels, each equipped with a optimiser unit, all tied to s Solaredge SE3680 4Kw Inverter.  The total installed capacity is rated at 3.96KWp or 8.54 KWac. 

Plugging these stats together with the southern angle, plane elevation and shading factors, the Annual Solar PV Yield was predicted via the MCS method and PVsol simulation to be around 3277Kwh per year. Factoring in panel degradation, energy price inflation and the guaranteed FIT tariff (12.03p/kWhr) and export tariff rates (4.85p/kWhr), I am predicted a return of just under 12k over the next 20 year period. The system cost about £6.5k to install with the 20yr kit warranty. O/c this payback is realised over the long term with both the FIT payments as income and cheaper electric bills.

The predicted and actuals over the past month are below: 

*Month
last
updated
 
Est. Generation Est FIT, Export income & Savings Actual   
Month kWh % of total Month Quarterly
(Running total)
kWh % of Est
Jan 166 2.83% £20.35   10   -
February   166 5.08% £36.52   187  111%
March 304 9.27% £66.67 £123.54 310  102%
April    367 11.21% £80.68   393  107%
May 440 13.43% £96.65   502  112%
June 432 13.19% £94.87 £395.45 482  110%
July 417 12.71% £91.45 £262 Paid from SSE, est. £133 saved on bill 430  103%
August 381 11.63% £83.66   460   -
September 292 8.90% £64.04 £634    
October* 211 6.43% £46.30 est. £230 due from SSE (tbc)    
November 122 3.71% £26.72      
December 53 1.61% £11.56 £719.47    
YEAR 3277 100.00% £719.47 £719.47    

 

Happily, so far I have generated more per month than the estimated - an average of 108% infact. This can only be a good thing but I have yet to compete the estimated bill savings against reality, which may eat up the extra 8% gain. Only time will tell. (updated Oct 5, 2016) 

Solar PV, Aberdeen and me

Jan 202016

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Around January this year, I invited the chaps from AES Solar round to quote me for the installation of solar panels on the roof.

Up to that point I had received a few quotes from other installers, gripped as I was by the impending cut-off date before the tariff dropped. For those that are not aware, many of those opting to install panels do so not just for the green karma (although the true 'greenness' of solar has yet to be totally proven in my eyes) but also for the financial return.  In a nutshell, anyone installing prior to January 13th 2016 is paid at least 12.04p per kWHr returned back to the national grid - the so-called 'Generation Tariff'. You also get an additional export tariff per kWh you export, which is currently 4.85p.  Those who installed Solar panels earlier received much better tariff rates, but this has be offset against the high costs of install back then.

Now or never

Assuming you managed to find a good installer, January 2016 was a good time for PV install. This was primarily down to two reasons:

  1. Hardware was the cheapest it had been due to manufacturing advances etc, and
  2. Tariffs were then due to sharply drop of a cliff by 80%.

Why the drop? well officially the government reasoned that more efficient and affordable panels meant the top-up paid to consumers to 'go green' need not be so attractive. I have since read that a second reason for dropping the tariff was that the uptake was higher than expected which was costing the government rather too much. Whatever the reason, a post-Jan16 install was not going to be quite as lucrative and so if I was ever going to sink some savings into my house in this way, it really was now or never.

The two quotes I had received over xmas all contained recommendations for panels on both roof planes of my house. The maximum size of domestic installation that the government will support via FIT is 4kW, which would on my total roof space. I have SSE facing and NNW facing roof spaces and whilst the NNW plane would get some light at sun rise and sunset, it did not feel great knowing that for most of any given sunny day, the NNE panel array would receive considerably less light (see seasonal sun plots below).   

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Summer prediction (End June)


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Winter Position (Late December)

The summer sun will reach the north-facing roof, but it will be late in the day when the sun's intensity is much less. It seemed that getting as much sun coverage facing south during those peak hours was preferred but the problem was a lack of southern roof space. The installers I worked with were very accommodating and allowed me to incorporate a 'house addon' in to the array layout. This would be a temporary structure that will accommodate the remaining panels in the beneficial direction. 

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 'Lean to' design to accommodate the extra panels.

To proceed with the design, one panel has to be placed on the wall but I was not particularly put off by this. The structure was built, the panels installed and the whole system commissioned 3 days before the cut off date for the old tariff (phew). I will post an update with the predicted earnings/savings some point soon.

Building a Low-pass filter (LPF) for WPSR Tx ( e.g. a Raspberry Pi)

Nov 202015

I found a nice set of guidelines about how to build LPF board for your transmitter. Only if your radio license lets you, I recommend having a go with one of these and a Raspberry pi [0]. 

For the low-pass filter, I am following a PDF guide [1] authored by Revd. George Dobbs (G3RJV).  The kit list is as follows:

  • 3 toroid cores (type FT37-43)
  • 1m enamelled copper wire (AWG tba)
  • 1 Choc box electrical junction box 
  • 1 case mounted BNC connector (male)
  • 2m 50ohm Coax
  • Capacitors (varied) 
  • Stripboard
  • Solder + iron 
  • An online toroid calculator [2] (if I must, and even then only to check)

We have to calculate the windings from the core size, material and desired inductance. Our design calls for 3 coils and 4 caps.

W3NQN's 7 Element standard Value Capacitor low pass filters

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Calculating number of N turns required on a Toroid for a given inductance:

N = 10 x SQUARE-ROOT ( L / L10)

N = Number turns.
L = Required inductance (uH).
L10 = Inductance at 10 Turns.

This design can be soldered onto strip board along with the antenna connectors of your choice. For the enclosure, I can recommend a choc-box connector housing from Screwfix (UK)[3] I have a few of these ready for projects and they work very nicely.  If you are very lazy, you can pick up complete LPF filters from  arp-labs.com [4]. They have a good selection and ship anyplace (also check-out their other kits) 

[0] https://github.com/JamesP6000/WsprryPi
[1] http://www.gqrp.com/harmonic_filters.pdf 
[2] http://www.66pacific.com/calculators/toroid_calc_how_to_use.aspx 
[3] http://www.screwfix.com/p/debox-in-line-connector-box/8692H?kpid=8692H
[4] http://www.qrp-labs.com/lpfkit.html 

 

Camp oatcake hacking

Aug 242015

The traditional oatcake is a very simple thing to make (perhaps the most simple) and as a result, is a great food to explore cooking on the campsite.

Tellingly, the food has it origins in the kitbags of the Scottish infantry where the food evolved as a quick means to cook a highly available food stuff into a meal. Medium ground oatmeal was bagged and packed for long marches, then mixed with fat and water, balled up and flattened onto a standard-issue metal plate. The plate was then held over a flame and cooked as if over a griddle, flipping when the edges brown. This makes a simple meal for the squaddie on the go and as a food recipe, it offers us a very nice platform to experiment with flavours.

Recipe:

1 cup of oatmeal (medium grade)

1 table spoon of butter, melted

1 half cup of water or milk (or 1 egg white if course meal is used)

Pinch of salt and/or sugar


Method:

Mix the oatmeal, salt, fat and water/milk/egg binding agent in a bowl until you are able to make balls of mixture that flatten without breaking apart.

Ball up golf ball sized portions of mixture and flatten out onto a greased pan. Hold the pan over a camp fire/stove until the edges just start to brown. Flip and cook on the reverse side.

Place on a tray to cool.


Some might argue that oatcakes are not the most flavoursome food on their own, tasting much like thinly-salted porridge biscuits. The easiest way to change the flavour of an oatcake is to replace the added salt with something else e.g. additional sugar, spices or herbs. You can also swap the fat for something more flavoured, such as coconut oil. Store brought essance flavourings are easy to throw in and certain wild combinations produce interesting and cheeky results. We experimented with a number of them:

  1. Vanilla and cinnamon 
  2. Citrus essences, such as lemon/lime with added sugar.
  3. Rose water
  4. Peppermint and bitter orange. 

Dried and powered foodstuffs such as seaweed (good for unami) are also interesting options. Just add more or less water/milk to help it all bind.

Happy food hacking!