This is the Tardis of Dr. Who equipped with a display and a CO² sensor. You can use it e. g. in the office to indicate the need for ventilation.

I am using a high quality CO² sensor. It uses the NDIR measurement technology. More information can be found here.

Tardis

As base I have used this thing.
Print the following parts from there:

• Base (either ring or solid)
• Panel with door
• Panel (2x)
• Window (2x)
• Top ring
• Roof
• Lamp shade
• Lamp top

From here you need to print

• tuer_display
• befestigung_display

Electronics

Following parts are needed

• Wemos D1 mini
• Sensirion SCD30 CO2 sensor
• 2.2 '' display ILI9340
• Micro-USB cable

There are three holes on the back of the modified door. The bracket can be glued to these holes to fix the display. The pins of the display are up.

Only two doors are equipped with windows to allow some ventilation. I have glued the sensor with the connection pins to the open window opposite of the display.

Wiring

Sensirion -> Wemos D1 mini

• VIN -> 5V
• GND -> GND
• SCL -> D1
• SDA -> D2

Display -> Wemos D1 mini

• SDO -> D6
• LED -> 3V3
• SCK -> D5
• SDI -> D7
• DC -> D3
• RESET -> RST
• CS -> GND
• GND -> GND
• VCC -> 3V3

Software

Install following libraries in your Arduine IDE:

• Adafruit GFX
• Adafruit ILI9341
• TinyWireM

Compile and upload the sketch display_hochkant.ino to the Wemos D1 mini.

Here you can find more information on the display in German.

And on this Github repository you can find other sample code for the CO² sensor.

To assess the measured CO² concentration this page was helpful for me (in German).

Have fun with the Tardis!