Hardware Requirements

• Raspberry Pi Zero w/ WiFi or similar
• PMS7003 or PMS5003ST sensors (the latter one is able to sense formaldehyde, temperature & humidity)
• Waveshare 3.5" inch display for Raspberry Pi
  • if you want to retrofit backlight control to it, then you will need a couple of electronic parts - more details here
• TSL2561 (GY-2561) I2C light sensor to control the brightness thru GPIO PWM output via optocoupler and NPN transistor (see above)
• Hub USB hat
• Prototype board for RPi Zero
• mini USB soundcard - try to find not the cheapest one, but rather a good quality one that has a good microphone signal (no noise etc, read some DIY reviews)
• a mini microphone of decent quality
• a mini speaker (like MG15 0.1W 8ohm) plus amp module
• 16GB SD card (as fast as possible due to voice assistant and its responsiveness)
• optionally RTC module (like TINY RTC DS1307 running on I2C)
• a fan to cool PMS5003ST laying close to kinda warmish LCD display, so it can read a real temperature (connected the fan to 3V so it is quiet and still does the job)