TheBitterEnd said:
Well there is this
http://interestingto.me.uk/Open%20Source/low-cost-low-power-datalogger which I am just ironing a few wrinkles out of but it is nearly there.
There does seem to be a bit of a need for something like this, however it is not the easiest thing to solder (esp. the SD card holder where the pins are underneath) so if a few people were interested it could be worth getting a batch made up. Everything except the SD card holder could be through-hole rather than SMD if people wanted that.
Would you really want to sample it every second? I can't see that a draft would vary that quickly...
Looks very good, but as I am no techie, so some clarification please. As I understand your project, the data is pushed to an SD card, so there is no problem about holding a quantity of data.
The speed of the ATMEGA168-20AU suggests it can cope with much faster data acquisition times than my suggested 1 sample per second. Any ideas on top speed? Whilst I have no idea how the air movements could vary, I guess the sensor will have a fair sized thermal lag with respect to 1s. So perhaps one can sample at a slower rate. But other potential uses might desire faster rates; our work on rope goes up to10us per sample for example.
I understand it will take both analog signals and digital data. I presume the analogue voltage supplies have to be limited. 8 bit operation means data precision is around 0.4% which should be more than enough for most applications.
I guess there will have to be a fair amount of instructions if it is to be used by non programmers.
Bottom line is what cost?
In reply to Rob, one could use a second detector which is shielded to obtain temperature or use
http://moderndevice.com/product/sht21-humidity-and-temp-sensor/