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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Over two years ago I wrote this article about giving an MLX90614 a new slave address, different from the default they are all set with from the factory (0x5A), in order to enable having more than one individually addressable device on the bus.

As before I am still using two of these MLX90614 sensors in my cloud detection project and have changed slave addresses on these devices many times before with very few problems.

Why am I writing a new post about this? Well I have had quite a few questions on my original article and I decided to hopefully make a few things a little clearer with some updated code examples thrown into the mix.

What are we going to do in this article? Focus on the following:

1. Take a quick peek at the MLX90614 again
2. Look at some updated code for changing slave addresses
3. See the range of supported addresses
4. Look at actually running the code

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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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This is a little project to build a cheap UV exposure box for developing UV sensitive printed circuit boards.

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I've been testing out the Arduino Yún recently with a view to making use of one in a project. I've come across a problem or two and solutions that were probably worth making a note of, so I thought that I'd write them here as somewhere to come back to in future.

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This article mainly concerns the many trials of reliably bringing a remotely installed cloned Arduino and Wiznet W5100 Ethernet shield back to life after a power cut. The W5100 board is being explored as an alternative to the cheaper 28J60 board which itself ended up with its own reliability issues as described here in another article.

Please note that this particular article references DCcduinos only. The problems described within do not affect a genuine Arduino in my experience.

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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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