This post follows on at quite a distance from my last post on the subject, and until recently I had not realised quite how long this project has been languishing on the bench. Like many of the electronics projects I undertake they need to be able to withstand being outside and exposed to weather conditions, dealing with packaging them to handle harsher environments is always the most difficult part.

For the same reason as above, I have also changed one of the key measurement components, the humidity sensor.

I am also dropping the Arduino Uno in favour of the Arduino Yún. I wrote a brief article on the Yún some time ago.

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I spotted some unusual clouds over the house the other day!

Panorama shot of mammatus over the house

I have always enjoyed identifying clouds and if I can take pictures of any unusual formations. This type, Mammamtus, is pretty rare in these parts; I can count on one hand the number of times I have seen Mammatus clouds.

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It has been a while since I made any progress on a project, so I thought that I would put something down here as a way of summarising to myself where things are, what is left to do and so on, as a form of to-do list.

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How would one be able to restart a system that has been deployed in a remote area which gives no immediate access for human intervention? The answer is to give the system an ability to reset itself in case of a system crash.

This is where a watchdog timer (WDT) comes into use. It is a hardware based timer capable of automatically resetting a system should the main program fail to periodically send out a heartbeat. Now, the Arduino does indeed have a WDT on board, as do probably all microcontrollers, but a small amount of reading will inform you that once it has started running a sketch, there is no software function that has the same effect as pressing the reset button.

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Some would say that at this stage I was almost there with the soil sensor project. All there was left to do was get the thing into the ground. Being that I am a flawed perfectionist, I had some other ideas . I was not going to simply chuck it in the ground without some more prevarication.

Anyway, onwards...

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A very brief part three of the, somewhat delayed, soil temperature monitoring project. This project has been left a little on the side gathering dust whilst I spent some time concentrating on the cloud detection project, but I am now determined to get this system up and running and its sensors in the ground before the winter weather sets in. Being in the ground soon will also mean that I get a good run before the cold weather hits.

At this point I have progressed with getting the electronics from breadboard to circuit board, well, Veroboard anyway. Also, the mission has crept slightly: after some more research, I have decided that the project is to become more of a surface/ground temperature station with the addition of minimum grass and concrete temperature measurements.

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This post follows on quite quickly (for me at least!) from my last one regarding my latest tests and reflections on environmental issues with some thoughts about how to measure ground temperatures in a reliable way. I am also going to take a look at the difficulties I might face in trying to automatically interpret cloud cover the whole year through. Finally I am going to share some thoughts on how I might approach packaging the system for deployment in the open air, and what to do about supplying power and communications.

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Since the last part in this series I have continued to conduct experiments comparing and contrasting the two variants of MLX90614, the wide field of view BAA and the considerably more focused BCF. Whilst undertaking these 'in the field' tests I have also come up against a few, what you might call, environmental problems which need addressing before I can move from the prototype phase to the implementation phase.

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Part two on the soil temperature monitoring project. Detailing some thoughts on how to get the sensors in to the ground in a way that will keep them protected from the underground environment. Following that, some subequent details on the construction of the sensor housings.

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This project has its roots in a chance sighting of some, what I thought were, interesting looking API parameters on the Met Office weather data submission service. I've been running a small weather station for about a year with its data output being harvested by a RaspberryPi and packed off to the Met Office observation service.

Many months ago a friend and I were idly browsing to see what other interesting data people were collecting and sending there when we spotted, to our surprise, soil temperature measurements using sensors buried at 10, 30 and 100 centimetres. These depths are certainly not arbitrary; they may represent three of the many soil horizons: A, B and C (See the Wikipedia page regarding soil horizons). This sparked off a thoughts on the possibilities of home made sensing, gathering and aggregating soil temperature readings to a service on the internet.

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