📖 What You'll Learn in This Tutorial:

✓ Understanding the ESP8266 D1 Mini pinout
✓ Wiring relays to the D1 Mini
✓ Connecting DHT22, DS18B20, and NTC sensors
✓ Power supply requirements
✓ Common wiring mistakes and fixes

ESP8266 D1 Mini Overview

The ESP8266 D1 Mini is the most popular board for OceanRemote. It's small, inexpensive ($3-5), and powerful enough for most home automation projects.

📏 D1 Mini Specifications:

Microcontroller: ESP8266 (ESP-12E module)
Operating Voltage: 3.3V (5V tolerant on some pins)
Input Voltage: 5V (via USB) or 5-12V (via VIN pin)
Digital I/O Pins: 16 (D0-D8, D10-D16)
Analog Input: 1 (A0, 10-bit ADC, 0-3.3V)
Flash Memory: 4MB
RAM: 80 KB

Pinout Diagram

                    ESP8266 D1 Mini Pinout
            ┌─────────────────────────────────────┐
            │  ┌───┐                              │
            │  │USB│                              │
            │  └───┘                              │
            │                                     │
            │  D0  ────┐  ┌────  D8               │
            │  D1  ────┤  ├────  D7               │
            │  D2  ────┤  ├────  D6               │
            │  D3  ────┤  ├────  D5               │
            │  D4  ────┘  └────  D4 (LED)         │
            │  D5  ────┐  ┌────  3.3V              │
            │  D6  ────┤  ├────  GND               │
            │  D7  ────┤  ├────  RST               │
            │  D8  ────┘  └────  A0               │
            │           3V3  GND  RST  TX  RX      │
            └─────────────────────────────────────┘

Pin to GPIO Mapping

Board Pin	GPIO	Function	OceanRemote Use
D0	GPIO16	Wake from deep sleep	Not used
D1	GPIO5	I2C SCL	Relay 1
D2	GPIO4	I2C SDA / Sensor	Relay 2 + Sensor
D3	GPIO0	FLASH button	Relay 3 (⚠️ boot caution)
D4	GPIO2	Built-in LED	Relay 4 (⚠️ boot caution)
D5	GPIO14	SPI CLK	Relay 5
D6	GPIO12	SPI MISO	Not used
D7	GPIO13	SPI MOSI	Not used
D8	GPIO15	SPI CS	Not used (⚠️ boot caution)
A0	ADC	Analog input	NTC Thermistor

⚠️ Critical Boot Pin Notes:

GPIO0 (D3) - Must be HIGH at boot. If pulled LOW, board enters flash mode.
GPIO2 (D4) - Must be HIGH at boot. Built-in LED is active LOW.
GPIO15 (D8) - Must be LOW at boot (connect to GND with 10k resistor if used).
GPIO1, GPIO3 (TX/RX) - Used for Serial communication. Avoid using.

OceanRemote's default pin selection avoids boot issues by not using GPIO15 and using D3/D4 with care.

Wiring Relays to D1 Mini

OceanRemote uses 5 relays by default. Here's the recommended wiring:

Relay	D1 Mini Pin	GPIO	Relay Module Connection
Relay 1	D1	GPIO5	IN1 → D1, VCC → 5V, GND → GND
Relay 2	D2	GPIO4	IN2 → D2, VCC → 5V, GND → GND
Relay 3	D3	GPIO0	IN3 → D3, VCC → 5V, GND → GND
Relay 4	D4	GPIO2	IN4 → D4, VCC → 5V, GND → GND
Relay 5	D5	GPIO14	IN5 → D5, VCC → 5V, GND → GND

💡 Relay Logic:

Positive Logic (🔺) - Relay turns ON when pin is HIGH (3.3V). Default for most relay modules.
Negative Logic (🔻) - Relay turns ON when pin is LOW (0V). Use if your relay module is active LOW.

Most cheap relay modules use Negative Logic (LOW = ON). You can change this in the device configuration page.

Wiring Sensors

DHT22 Temperature & Humidity Sensor

DHT22 Pin	Connect to D1 Mini
VCC (Pin 1)	3.3V or 5V
DATA (Pin 2)	D2 (GPIO4)
GND (Pin 4)	GND

DHT22 Wiring:
┌─────────┐                    ┌──────────┐
│ D1 Mini │                    │  DHT22   │
├─────────┤                    ├──────────┤
│   3.3V  ├────────────────────┤ VDD (1)  │
│    D2   ├────────────────────┤ DATA (2) │
│   GND   ├────────────────────┤ GND (4)  │
└─────────┘                    └──────────┘

DS18B20 Digital Temperature Sensor

DS18B20 Pin	Connect to D1 Mini
VDD (Pin 3)	3.3V
DATA (Pin 2)	D2 (GPIO4)
GND (Pin 1)	GND

⚠️ DS18B20 Requires Pull-up Resistor!

A 4.7kΩ resistor must be connected between DATA (D2) and 3.3V. Without it, readings will fail.

DS18B20 Wiring (with pull-up):
┌─────────┐                    ┌──────────┐
│ D1 Mini │                    │ DS18B20  │
├─────────┤                    ├──────────┤
│   3.3V  ├────┬───────────────┤ VDD (3)  │
│         │    │               │          │
│    D2   ├────┼───────────────┤ DATA (2) │
│         │    │    4.7kΩ      │          │
│   GND   ├────┼────[====]─────┤ GND (1)  │
│         │    │               │          │
└─────────┘    │               └──────────┘
               └────────────────┘

NTC 10kΩ Thermistor (Analog)

The NTC thermistor requires a voltage divider circuit to work with the D1 Mini's ADC.

Component	Connect to D1 Mini
NTC Thermistor	Between 3.3V and A0
10kΩ Resistor (R_series)	Between A0 and GND

NTC Thermistor Voltage Divider:
         3.3V
          │
          ▼
        ┌───┐
        │NTC│  ← 10kΩ NTC (resistance changes with temperature)
        └───┘
          │
          ├──────► A0 (ADC)  ← Voltage measured here
          │
        ┌───┐
        │10k│  ← Fixed 10kΩ resistor (R_series)
        │Ω  │
        └───┘
          │
         GND

Power Supply Requirements

USB Power (Recommended for Testing)

Use a quality USB cable (not charge-only)
5V, 500mA minimum (1A recommended with relays)
Phone charger works well
Computer USB port works (but may be limited to 500mA)

External Power (For Permanent Installation)

Connect 5-12V DC to the 5V pin (regulated power)
Or use the VIN pin for unregulated 5-12V (board has voltage regulator)
Relay modules should share the same power supply
Total current: ~200mA (D1 Mini) + 70mA per active relay

⚠️ Power Warning:

Do NOT power relays from the D1 Mini's 3.3V pin! Relays need 5V. Use the 5V pin or an external power supply.

Complete Wiring Diagram

Here's a complete wiring diagram for a D1 Mini with 5 relays and a DHT22 sensor:

                    COMPLETE D1 MINI WIRING
            ┌─────────────────────────────────────────────────────┐
            │                                                     │
            │  ┌─────────┐      ┌─────────────────────────────┐  │
            │  │ D1 Mini │      │      5-Channel Relay Module  │  │
            │  ├─────────┤      ├─────────────────────────────┤  │
            │  │   USB   │      │  IN1 │ D1 │ GPIO5           │  │
            │  │   5V    ├──────┤  IN2 │ D2 │ GPIO4           │  │
            │  │   GND   ├──────┤  IN3 │ D3 │ GPIO0           │  │
            │  │   3.3V  ├────┐ │  IN4 │ D4 │ GPIO2           │  │
            │  │   D1    ├────┤ │  IN5 │ D5 │ GPIO14          │  │
            │  │   D2    ├────┤ │  VCC │ 5V │                 │  │
            │  │   D3    ├────┤ │  GND │ GND│                 │  │
            │  │   D4    ├────┘ └─────────────────────────────┘  │
            │  │   D5    ├──────┐                                │
            │  │   A0    │      │    ┌─────────────────────┐     │
            │  └─────────┘      │    │      DHT22 Sensor    │     │
            │                   │    ├─────────────────────┤     │
            │                   └────┤ DATA │ D2            │     │
            │                        │ VCC  │ 3.3V          │     │
            │                        │ GND  │ GND           │     │
            │                        └─────────────────────┘     │
            └─────────────────────────────────────────────────────┘

Common Wiring Mistakes

Mistake 1: Relay Module Powered from 3.3V

Problem: Relays don't click or work intermittently
Fix: Connect relay VCC to 5V (not 3.3V)

Mistake 2: Missing Pull-up on DS18B20

Problem: Sensor reads -127°C or fails
Fix: Add 4.7kΩ resistor between DATA and 3.3V

Mistake 3: Wrong GPIO for Relay

Problem: Board doesn't boot or relay behaves strangely
Fix: Avoid GPIO0, GPIO2, GPIO15 for relays if possible (OceanRemote uses them but they're safe with proper logic)

Mistake 4: Floating Sensor Pins

Problem: Random temperature readings
Fix: Ensure all sensor pins are connected properly

Mistake 5: Power Supply Too Weak

Problem: Device resets when turning on relays
Fix: Use a stronger power supply (2A recommended for multiple relays)

💡 Testing Before Wiring:

Start with just the D1 Mini connected via USB. Get the firmware working first, then add relays one at a time, then sensors. This makes troubleshooting much easier.

Next Steps

Now that you understand the wiring, continue with:

Tutorial 11: ESP8266 D1 Large Pinout and Wiring
Tutorial 12: ESP32 Pinout and Wiring Guide
Tutorial 13: Raspberry Pi Pico W Pinout and Wiring
Return to Tutorial 02: Generate and flash your firmware!

🎯 You're Ready!

Your D1 Mini is now properly wired. You can now generate firmware from the OceanRemote dashboard and flash your device!

Tutorial 10: ESP8266 D1 Mini - Pinout and Wiring