Quantity   Component name
1 × DigiSpark ATMega85 devboard on a USB plug. Typically a clone..
1 × DHT11 Cheap-ass Temperature and Humidity sensor
1 × NPN signal level Mosfet eg IRLZ14, IRL520, or similar. Big enough to switch the fan you use even when stalled or starting.
2 × Diode 1N4007 reverse voltage and flyback protection
4 × Resistors for the voltage detector divider, and the mosfet drive.
1 × Miscalaneous connectors for PCB, Pin connectors and screw. 3pin power connector (screw type), 2x 3pin for the DHT11 and DigiSpark power. 1x 6pin for the DigiSpark data pins