Cloud Sensor Project

[Ian]

I need to have a bit of a read, but you could make a thermocouple from some lengths of constantan and copper wire. A difference in temperature between them can be measured directly as a voltage, regardless of the absolute temperature. A microcontroller with an analogue input should be able to sense that voltage (particularly if it has a high input impedance). Don't forget if you're reading small signals, Op amps can be used as an amplifier quite easily.

[Mike]

Sounds like ahrd work Ian!

OK I have ordered :-

1 x Arduino Diecimila - http://www.arduino.cc/en/Main/ArduinoBoardDiecimila
3 x DS18B20 - http://www.maxim-ic.com/quick_view2.cfm?qv_pk=2812

I'll let you know how I get on.

[RobertM]

Good luck, especially with the API programming !

[Mike]

I'm planning on extracting the data from it using Python and then getting the PC to set off alarms depending on set criteria. It will also log the data so I can create pretty graphs and keep a nice history of clear/cloudy skies.

A later project will be to post that information to a data stream on my website (probably using JSON) to allow other people in the Orpington Area to also run the program to set off alarms on their own PC's.

[RobertM]

You should be ok doing it in Python.  I want to learn that too one day but we don't use it much where I am at the moment - it's mainly perl. 

[Mike]

I've been using Python for a while now and love it. Very easy and yet very powerful language. Recently learning Objective-C for OSX which is fun....  NOT!!

[Rick]

Scripting languages can be a headache. I've had to deal with stuff in JavaScript, PHP, Perl, Ruby, Python, sundry unix-ish shell-scripts, and then some... Never found one I really liked. It'd be nice to throw most of them away. 

Next step up (down? sideways?) is probably something like Java.

C#, C++, Objective C, and the rest are mainly for the rabidly insane^*1, to be used only when nothing else will work.

^*1 Any inferrence drawn from this statement is entirely the product of a derranged immagination.

[Mac]

If you want to have a go in visual basic.
I can lend you visual studio.

Should be easy to get to grips with, and you can design some nice interfaces.

And if you are feeling insane, you can do it in visual c#

Mac.

[Mike]

I've got VS thanks. I was considering doing it in C# but Python would be easier. I am wondering if a web based app rather than one you install might be a better option. If so i'd use Python or Java.

[Mike]

Well the temperature sensors arrived last week and the Arduino board arrived today. Surprised how small it is.

So, will be tinkering around over the next few days to try and get a cloud sensor up and running. i will let you know how it goes.

I have been reading up on these Arduino boards and you can do an amazing amount of things with them. There are hundreds of websites with home built projects for all kinds of cool stuff using them. I will have to have a think about what kind of astronomical gadget I could make using one as well as the cloud sensor. Such as this device - http://www.cibomahto.com/?p=249 - for controlling the Nikon D70 via IR to give more than 30 seconds exposures.

There is a wireless board available for it so the Cloud Sensor could be installed anywhere and transmit it's data back to the PC via a wireless link (later project maybe).

If this cloud sensor is successful I will be happy to build one for anyone that wants one. I am guessing cost of the entire thing will be around £50 assembled.

[Mike]

I spent a few hours last night tinkering around with the Arduino and uploading some code to it. I started with the old electronic version of the "Hello World" program by getting it to flash an LED at different rates.

Then moved on to connecting up one of the DS18B20 temperature sensors and after about an hour of frustration ended up with getting a reading of 26 degrees C which went up if I put my finger on the sensor (I had failed to connected a pull-up resistor between the data line and the +5v). This was definately higher than the temp in the room but I was using code I found on the net for a DS18S20 sensor just to try out the sensor so I presume the values are slightly different. I will need to read the datasheet for the DS18B20 to be able to work out the hex values it gives off so I can modify the code to give accurate values.

Once that is successful I can connect up the other 2 sensors (I want 2 for the cloud sensor and one to give an internal temperature) and get readings from them. Then I need to write code to work out if it is cloudy/partly cloudy/clear and experiment with the settings.

[RobertM]

If this cloud sensor is successful I will be happy to build one for anyone that wants one. I am guessing cost of the entire thing will be around £50 assembled.

Might possibly take you up on that.  Could form an excellent base for an observatory control system and could remotely power up the PSU I built since it has that capability.

[Mike]

Yea it would be easy to control any kind of electronic or electrical device from the Arduino, such as open/close a roof, power down kit, send signals to a PC, etc.

[RobertM]

Might be an excuse to learn some Python, what's the API like to program with ?

[Mike]

I've yet to do any program on the PC to interface with the Arduino. So far I have just coded the Arduino microprocessor itself which you do using a C++ like language (though much simpler) on the Arduino IDE. The IDE has a Serial Monitor to allow you to read the serial data output from the device directly.

There are various libraries for most of the popular languages to allow you to interface with the device via serial - http://www.arduino.cc/playground/Main/InterfacingWithSoftware