For this Project, I used an esp8266 thing from Sparkfun.
- 1000mAh 3.7V Li-Po Battery
- black plastic box
- Wi-Fi Antenna with adapter cable for the board
- microSD card module
- DS1307 RTC module (terrible one!)
- on / off switch for the Li-Po battery
The software scans for available networks every few secconds and outputs the SSID (name of the Wi-Fi), encryption type and RSSI (received signal strength) in csv format to the SD card.
Scanning for Wi-Fi networks is a very power consuming task. The average peak current drawn from the battery is around 300mA. The deep sleep mode of the esp8266 comes in very handy for this battery powered application.
Right: Power consumtion of the network scanner. Peak signal in [mV] on a series resistor of 1Ω therefore 350mV = 350mA.
On the diagramm above, the scanning takes approximately 3s to complete. So for a scan intervall of 15s, the deep sleep duration is 12s.
The collected data is in the csv format and looks like this:
You can now create good looking graphs in Microsoft Excel or something like that.
I put my warcamping device behind a ticket vending machine at the main station and was able to capture some hotspots of smartphones. The graph on the right is a good example of someone just passing by the tickt machine. The graph on the left shows someone passing by the twice in a very short time period (signal is not lost)
On this graph a person with a hotspot was at the main station twice this day. Once at 07:12 o'clock in the morning and once at 13:22 in the afternoon.
I also captured some funny names like:
- Don’t even think about it…!
- HP-Print-B7-Officejet 6700
Note the printer - on a train. People like bringing strange things on the train.
Another fact is, that all the 46 networks detected during the day were encrypted with WPA-PSK2. (Except for the 4 open public networks)