💧 DIY Air Humidifier

This project is a simple humidity-based controller for a 5V ultrasonic humidifier, using an Arduino Nano, DHT11 sensor, potentiometer, NPN transistor, and a TM1637 4-digit display.

When the humidity drops below a user-defined setpoint, the system automatically powers on the humidifier. The setpoint is adjusted via a potentiometer, and both the setpoint and current humidity are shown on the display.

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🧰 Components Used

• Arduino Nano (Rev3.0)
• DHT11 Humidity & Temperature Sensor
• 10kΩ Potentiometer or Trimmer
• TM1637 4-digit 7-segment display
• NPN transistor (e.g. 2N2222 or S8050)
• 220Ω resistors (×2)
• 5V ultrasonic atomizer
• Breadboard & jumper wires
• Power source (USB or 5V supply)

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📐 Circuit Overview

• The DHT11 measures ambient humidity.
• The potentiometer sets the desired humidity setpoint (30%–70%).
• A TM1637 display shows:
  • First two digits: setpoint (e.g. 45)
  • Last two digits: current humidity (e.g. 38)
• An NPN transistor switches on the LED and humidifier when humidity is below the setpoint.
• Everything is powered at 5V, and controlled by the Arduino Nano.

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💾 Libraries Required

Install via the Arduino Library Manager:

• DHT sensor library
• TM1637Display

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📟 Display Output

Setpoint: 45% Humidity: 38% Display: 4538

When the humidity drops below the setpoint, the transistor activates, powering the LED and humidifier.

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📸 Project Preview

Note: instead of the led, a 5V ultrasonic atomizer must be used.