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.
This is the ongoing project to measure cloud cover, as discussed in this series of articles. So, what's left to do?
As discussed I am still looking to package the system up using a combination of external mains junction box, various bits of plastic plumbing pipe and drainage pipe, expoxy resin and silicone sealant.
The IR sensor must be kept out of the way of inclement weather. This means housing it in such a way so that it takes its measurements indirectly via a reflecting surface, such as a home made polished aluminium mirror. Regarding how to deal with dew, the mirror must come equipped with a temperature sensor and heating element bonded to the rear non-reflecting surface.
The reflecting surface will at least partially be exposed to the sky thus necessitating a method or two of keeping dew at bay. I am currently thinking of constantly sampling the mirror temperature and using that to feed back to a light duty heating system, comprising a nichrome wire heating element, to keep the mirror a couple of degrees above dew point. Additionally I am considering using a small fan to keep air moving in the space between the IR sensor and the mirror.
Build a prototype circuit with an Arduino as a controller containing the following:
- A DHT22 humidity sensor and required code to calculate local dew point temperature.
- A DS18B20 temperature sensor for measuring the reflector surface temperature.
- A relay or transistor to control the reflector heating element and fan.
- A bicolour LED to indicate heating on / off.
- Write a brief blog entry about it in the projects section.
This system has spent well over a year working "in production". I've only had to address some reliability problems with the networking, as discussed here, by giving the Arduino a heartbeat and here regarding the W5100 ethernet shield.
This is a project I have thought about doing for years. Probably these days it may be cheaper to go an buy an internet-ready bird nesting box with a HD quality camera inside, but where is the fun in that? I have spent a few nights putting a few hours into the cunstruction of a bird box with space to fit a modified cheap USB web cam from my local Maplin store. I've retrofitted some bright IR LEDs to give a little light so that the chicks can be seen (and hopefully only gently warmed in the IR glow!). I have all the materials required to complete this project - the only other thing I need to think about is to write an entry or two on here at some point.
A friend at work and I have shared many an hour discussing Arduino projects, and after many circuits built using veroboard we decided to have a look at prototyping some custom circuit boards. Not being up for the old fashioned approach of drawing out circuits on board by hand, we decided to have a go at laser printing them instead. There is no need go through the whole process of how one can home-make PCBs, so here is a handy guide. It just suffices to say that we wanted to have a go at a UV exposure method for masking the circuit board prior to etching.
A little bit of research will tell you that these UV light boxes are quite expensive, so why not make a DIY version instead?
This is based on another thought that kept me awake one night (yes, I must learn to think about more interesting things!). Listening to the shipping forecast on Radio 4 I always wondered how the visibility was measured. Traditionally, of course, this was done simply with a manual observation of objects at known distances. These days measurements are taken using instruments using xenon beams and sensors separated by a short distance.
I got to thinking about whether I could do something similar using a cheap laser diode and a detector to measure the loss of light by scattering over a small distance in the garden.
At this stage the whole thing is a proof of concept and another excuse to spend a few hours in the workshop playing with electronics. I have a few ideas about how to build the thing and have started prototyping some small circuits. Again, it is probably time to start writing an article on here about it.