When I purchased my first Arduino I also grabbed a myriad of sensors. One was the Maxim / Dallas DS18B20 one-wire temperature sensor (PDF Spec). The cost was $17 for 5 sensors on 3 meter cables from amazon under the RioRand brand name. I didn't know what their intended purpose was going to do with them, but when I received my wifi module I figured I would put it all to use.
Some quick googling lead me to the Dallas Temperature Control Library. After connecting the sensors using a 10k resistor I loaded up the example sketch - success - I could see my temp probes!
The next task is to publish the data to some kind of database. In this case I elected to send the data to a PHP script which would simply write it to a CSV file.
Here we expand on the previous serial wifi code to send data via POST to a PHP script for processing.
This PHP script accepts POST data from the arduino and logs it to a CSV file.
I made a simple chart using Sencha ExtJs. You can see the data below. I'm limiting the output to the last 480 readings - which at once per minute gives 8 hours.
Using the INA219 current sensor from adafruit, actual current consumtion measured is on average 60.4 mA. This is with absolutely no power optimizations to decrease the current consumption for the arduino or wifi module.
| Component | Vendor | Cost |
| USR Wifi232-T w/ antenna | Ebay | $11 |
| 5pcs DS18B20 Temp Sensor 3M Cable | Amazon | $17 |
| 10k Resistor | Digikey | $0.10 |
| Arduino Nano (Clone) | Amazon | $12 |
| 9v 1A Regulated Power Supply | Adafruit | $7 |
| Female 2.1mm DC Power Jack | Adafruit | $2 |
| Total | $49.10 |
2014-10-24 Published
2014-12-28 Github code added
2015-1-8 Added Arduino Nano Wiring Diagram