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Mr. K. E. Varney "kev675" (Reading UK)
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SainSmart MG811 Gas CO2 Carbon Dioxide Sensor Module Sensor Module for Arduino
SainSmart MG811 Gas CO2 Carbon Dioxide Sensor Module Sensor Module for Arduino

1 of 1 people found the following review helpful
1.0 out of 5 stars I don't think it is a particularly easy sensor to use, 6 Nov. 2014
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I have been struggling with this for quite a while. I think I may have broken it. I bought it for an Arduino but I simply can't get it to work. The first problem I had was that it uses a 6V voltage rather than 5V that comes out of the Arduino. I tried using a 4 battery pack to power the sensor, but I was not sure the ground was the same ground as on the Arduino. Later I bought a A-D power converter and a couple of separable power jack connectors so that I split the 6V supply into the Arduino and the MG811 sensor. Another problem I had was that the signal output is quite low, only about 330 mV at normal atmospheric levels. Zero CO2 concentration would produce an output voltage of about 280 mV. To get any accuracy out of the Arduino, the signal has to be amplified to get several volts into an Arduino analog input. I tried an AD620AN instrumentation amplifier, but couldn't get it to work. Then I tried an LM358 op-amp and wired it up as a differential amplifier. It worked ok with a potentiometer posing as the MG811. However, when I plugged the MG811 in, the signal wandered up and down. The signal seemed different when it was plugged into the circuit to what it was when it was out. I thought maybe it needed a voltage follower, but it did not make any difference. Then the signal seemed to stabilize, but at a very low level, much lower than 280 mV. I think I must have broken it by then. Maybe I should have used a 30 ohm resistor between the 6V power supply and the MG811 power pin.

I have studied electronics in the past, but I am not a proper electronics engineer, so maybe it is just lack of competency on my part; however, I don't think it is a particularly easy sensor to use. I am tempted to buy a more expensive sensor with an inbuilt booster to boost the 5V from an Arduino to 6V needed to heat the sensor. That sensor also has a signal amplifier. However, that sensor is about twice the price, and this one was expensive enough, so it will have to wait for another time.


Faber & Kell's Heating & Air-conditioning of Buildings
Faber & Kell's Heating & Air-conditioning of Buildings
by Doug Oughton
Edition: Hardcover
Price: £95.00

3.0 out of 5 stars Comprehensive but not well written, 8 Jun. 2014
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I would say this is a reference book more than a course book. I read all the chapters, but I have to admit that I skim read most of them. Some of it was poorly written. There were spelling mistakes. There were errors in some of the charts. I started compiling a list of the errors I thought I had found, but gave up after a few chapters. It could really do with some editing. Despite that, there is a lot of information in there, and a lot of diagrams. If you need some information on some obscure heating or air conditioning system, it is probably difficult to beat.


The Body Economic: Life, Death, and Sensation in Political Economy and the Victorian Novel
The Body Economic: Life, Death, and Sensation in Political Economy and the Victorian Novel
by Catherine Gallagher
Edition: Paperback
Price: £23.95

4.0 out of 5 stars Strangely absorbing, but not easy., 8 Jun. 2014
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This is not an easy read, but quite an absorbing one. I bought it because it combined two of my interests: 19th century literature and economics. Four books were studied in detail: Hard Times and Our Mutual Friend by Charles Dickens, and Daniel Deronda and Tales of Clerical Life by George Elliot. The romantic poets are also mentioned, but only because of their interest in everything. Being a poet in the early 19th century entitled you to be taken seriously on any topic, so it would appear. The only one of those books I had read was Hard Times, which I have puzzled over quite a lot. It was not what I thought it was going to be like. On the one hand, I thought Dickens had something, on the other hand, I thought his arguments were confused. Catherine Callagher helped straighten all this in my mind and added another thought that had not occurred to me: what is the point of working so hard if it leaves you no time to enjoy anything. The book introduced two terms I had never heard of before: soma-economics and bio-economics. Bio-economics is about being able to get enough food to support your family and the limits on the population as a whole. Bio-economics spills over into sustainability and ecology. Soma-economics is whether the pleasure you get from being able to spend money is worth the effort of earning it. Robert Malthus is the founder of bio-economics; Jeremy Bentham is the founder of soma-economics, sort of. Plenty of other thinkers and economists had honourable mentions, including David Ricardo, Stanley Jevons, Herbert Spencer, Thomas Carlyle, Charles Darwin, Samuel Coleridge, Adam Smith, John Maynard Keynes, Percy Shelley and several others. It's all good, just not an easy read.


Vanishing Point [1971] [DVD]
Vanishing Point [1971] [DVD]
Dvd ~ Barry Newman
Price: £5.79

4.0 out of 5 stars Not bad actually, 26 April 2014
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This review is from: Vanishing Point [1971] [DVD] (DVD)
Better than I thought it would be. I thought it might be just a Cannonball Run sequence of car chases. There were a lot of chases, but it was a bit deeper than that. I liked all the back-story bits that explained why the driver was doing what he was doing.


Music From The Monks Kitchen [VINYL]
Music From The Monks Kitchen [VINYL]
Price: £24.13

1 of 2 people found the following review helpful
4.0 out of 5 stars Gentle, quite pleasant, sort of folk, 26 April 2014
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Initially I was a bit disappointed, but it grew on me. You have to be in the right mood. It is quite good music to chill to, especially if you have a young lady beside you, I would think.


What's Wrong with Climate Politics and How to Fix It (PWWS - Polity Whats Wrong series)
What's Wrong with Climate Politics and How to Fix It (PWWS - Polity Whats Wrong series)
by Paul G. Harris
Edition: Paperback
Price: £15.99

4.0 out of 5 stars Better at describing the problem than the solution, I suspect., 29 Dec. 2013
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I read this several months ago and cannot remember the details. I am no political scientist. The analysis of the problem sounded reasonable, but I was not very optimistic about solution.
If you believe anthropological climate change is scientifically real and a great danger to humanity and the biosphere, it is frustrating and dispiriting to see conference after conference fail. The author discusses at some length the Westphalian system, by which how a country governs itself is seen as its rulers' business and nobody else's. Currently the two biggest culprits in CO2 emissions are the USA and China. Without both these countries on board, any international treaty designed to rein in carbon emissions will fail to be effective. However, China will not sign up to any deal without the US, because they are historically more to blame. Meanwhile, the US will not sign up to any deal that does not oblige China and other developing countries to limit their emissions. In addition, the US will not sign up because of hostility in the American senate to the idea of man-made climate change. Partly for these reasons, the author thinks China should take the lead in negotiations.


The Leopard [1963] [DVD]
The Leopard [1963] [DVD]
Dvd ~ Burt Lancaster
Price: £9.14

0 of 1 people found the following review helpful
4.0 out of 5 stars Unusual film, political and intellectual, 29 Dec. 2013
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This review is from: The Leopard [1963] [DVD] (DVD)
I bought this DVD for two reasons:

1) Joan Bakewell recommended it on some three minute item on the radio.
2) I read the book years ago but had difficulty following it.

Not a bad film, very different to today's films. It is nearly three hours long so I watched it over three evenings. Burt Lancaster is very good. It's not his voice coming out of his mouth, because it is dubbed in Italian, but you would never know. It is rather an intellectual and political film. Times are changing in 19th century Italy and the aristocracy have to be shrewd if they want to keep their lands, not to mention their heads.


20A solar panel charge controller / regulator 12/24V for camper, caravan, boat or any other solar system with batteries
20A solar panel charge controller / regulator 12/24V for camper, caravan, boat or any other solar system with batteries

1 of 1 people found the following review helpful
2.0 out of 5 stars Does not seem very efficient, 6 Feb. 2013
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I bought this for a PhD project to replace another MPPT that had broken down. The MPPT that it replaced was a Morning Star SunSaver, which to be fair costs a lot more money. I was rather disappointed with the performance of this EP Solar unit. It is only about half as efficient as the SunSaver with the PV panel we're using. The voltage across the PV panel should be about 30 V, but the EP Solar holds it down to about 17 V, without increasing current flow to compensate. It could be that it is configured incorrectly, or that it would work better with a PV panel with a smaller operating voltage, but this was not obvious from the description.


Arduino Projects to Save the World
Arduino Projects to Save the World
by Brian Evans
Edition: Paperback
Price: £31.50

5.0 out of 5 stars Full of great tips., 2 Feb. 2013
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I am only part way through chapter 3, but I already feel confident enough to recommend it. It's full of great design tips, and also links to great components. Not all the advice is Arduino specific neither. I am sure many of the design tips could be used with other micro-controllers. I have been trying to use an Arduino as a data logger for a project. If I had had this book, it would have been much better.


Heat Pumps for the Home
Heat Pumps for the Home
by John Cantor
Edition: Hardcover
Price: £14.99

7 of 7 people found the following review helpful
5.0 out of 5 stars very good book on heat pumps and heating, 22 Oct. 2012
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This is a very informative book for anyone thinking about getting a heat pump for their home, but also anyone who is interested in them. There do not seem to be many books about heat pumps; this is the best of those I have read. It is written so the layman can understand it, although it would not hurt to be technically minded. It explains the theory, but is not just theoretical. It also describes a lot of the heating engineering type issues involved with the installion of effective heating systems. It discusses just about every type of ground loop, domestic heat pump, and heating system relevant to the UK domestic sector. I thought the best chapters were those on extracting the heat and utilising the heat. You can tell the author has a lot of experience these things. It is well illustrated throughout.


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