Precision Digital Thermostat (3 Zones)

Author: Bocaletto Luca

Files

• README.md
• PrecisionThermostat.ino

1. Concept

A three-zone thermostat that reads three DS18B20 temperature probes, displays each zone’s real-time temperature and setpoint on an OLED screen, and drives three relay outputs for heating/cooling. Users navigate zones and adjust setpoints via three push-buttons.

Key Features

• 3 × DS18B20 sensors on one wire bus
• OLED display (SSD1306 128×64) shows zone, temp, setpoint, relay status
• 3 push-buttons: Zone-select, Increase, Decrease
• Relay outputs with configurable hysteresis
• Non-blocking code for smooth UI and precise timing

2. Bill of Materials

• Arduino Uno (or Nano)
• 3 × DS18B20 waterproof probes + 3 × 4.7 kΩ resistors (pull-up)
• 1 × SSD1306 128×64 I²C OLED display
• 3 × SPDT relay modules (5 V coil)
• 3 × push-buttons + 3 × 10 kΩ pull-down resistors
• Breadboard, jumper wires, USB cable (5 V)

3. Wiring Diagram

DS18B20 Probes (all in parallel):
  ┌─────────────┐
  │ Data ──┬──► D2 (OneWire)
  │ VCC  ──┴─► 5 V
  │ GND ─────► GND
  └─────────────┘
  (4.7 kΩ pull-up from D2 to 5 V)

Push-buttons:
  ┌───────────┐       ┌─────────┐
  │ Select ─► D3   ──┤ Button  │
  │ Up     ─► D4   ──┤ Button  │
  │ Down   ─► D5   ──┤ Button  │
  └───────────┘       └─────────┘
  (Each button to 5 V, with 10 kΩ to GND)

OLED Display (I²C):
  ┌────────────┐
  │ SDA ──► A4 │
  │ SCL ──► A5 │
  │ VCC ──► 5 V│
  │ GND ──► GND│
  └────────────┘

Relays:
  ┌─────────────┐
  │ IN1 ──► D8  │ Zone 1 relay
  │ IN2 ──► D9  │ Zone 2 relay
  │ IN3 ──► D10 │ Zone 3 relay
  │ VCC ──► 5 V │
  │ GND ──► GND │
  └─────────────┘

4. Software Setup

1. In Arduino IDE, install libraries:
   • OneWire
   • DallasTemperature
   • Adafruit SSD1306 (and Adafruit GFX)
2. Create folder PrecisionThermostat and save these two files.
3. Open PrecisionThermostat.ino in Arduino IDE.
4. Select Arduino Uno and the correct COM port.

5. Usage

1. Power board via USB.
2. The OLED shows Zone 1 on startup.
3. Press Select to cycle Zones 1→2→3→1.
4. Press Up/Down to adjust the setpoint in 0.5 °C steps.
5. Relay engages when temp < (setpoint − hysteresis/2) and disengages when > (setpoint + hysteresis/2).
6. Zone temperatures and relay status update every second.

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Say continua to move on to project #6!