weatherstation/solar_schematics.md

Solar + Battery Powered Weather Station Schematics

Complete System Overview

Solar Panel (6V 2W)
    │
    ├───[Schottky Diode 1N5817]───┐
    │                            │
    ▼                            ▼
TP4056 Charging Module        18650 Battery
    │                            │
    ├───[Protection PCB]────────┘
    │
    ▼
3.3V Buck Converter
    │
    ▼
Wemos D1 Mini + Sensors

Detailed Circuit Diagrams

Solar Charging Circuit

Solar Panel (6V 2W)
┌─────────────────┐
│ +               │
│                 │
│ -               │
└─────┬───────────┘
      │
      ├───[1N5817 Schottky Diode]───┐
      │                           │
      ▼                           ▼
┌─────────────────┐        ┌─────────────────┐
│ IN+            │        │ +              │
│ TP4056         │        │ 18650 Battery   │
│ Charging       │        │ 3.7V 2500mAh   │
│ Module         │        │                │
│ OUT+           │        │ -              │
└─────┬───────────┘        └─────────────────┘
      │                           │
      └───────────[Protection]────┘

Battery Monitoring Circuit

18650 Battery (3.0V-4.2V)
    │
    ├───[100kΩ]───┐
    │             │
    ▼             ▼
   GND          A0 (Wemos D1 Mini)
    │             │
    └───[100kΩ]───┘

Power Distribution Circuit

Battery Output (3.0V-4.2V)
    │
    ▼
┌─────────────────┐
│ IN             │
│ 3.3V Buck      │
│ Converter      │
│ OUT            │
└─────┬───────────┘
      │
      ├───3.3V─────────────────────────────┐
      │                                 │
      ▼                                 ▼
┌─────────────────┐              ┌─────────────────┐
│ Wemos D1 Mini   │              │ Sensors         │
│                 │              │                 │
│ VCC             │              │ VCC             │
└─────────────────┘              └─────────────────┘

Complete Weather Station Wiring

Wemos D1 Mini Pin Layout
┌─────────────────────────────────────┐
│ D1 (SDA) ──────────────────────┐    │
│ D2 (SCL) ──────────────────────┤    │
│ D3 (LDR) ──────────────────────┤    │
│ D4 (DHT11) ────────────────────┤    │
│ D5 (LED) ──────────────────────┤    │
│ A0 (Battery) ──────────────────┤    │
│                                 │    │
│ 3V3 ──────────────────────────┼────┤
│ GND ───────────────────────────┼────┤
└───────────────────────────────────┘    │
                                      │
┌─────────────────────────────────────┐
│ Component Connections              │
│                                   │
│ BMP180 Sensor                      │
│ ┌─────────────────┐               │
│ │ VIN ───────────┼─ 3.3V         │
│ │ GND ───────────┼─ GND          │
│ │ SDA ───────────┼─ D1           │
│ │ SCL ───────────┼─ D2           │
│ └─────────────────┘               │
│                                   │
│ DHT11 Sensor                       │
│ ┌─────────────────┐               │
│ │ Pin 1 ─────────┼─ 3.3V         │
│ │ Pin 2 ─────────┼─ D4           │
│ │ Pin 4 ─────────┼─ GND          │
│ └─────────────────┘               │
│                                   │
│ Rain Sensor                        │
│ ┌─────────────────┐               │
│ │ VCC ───────────┼─ 3.3V         │
│ │ GND ───────────┼─ GND          │
│ │ AO ────────────┼─ A0 (Conflict!) │
│ └─────────────────┘               │
│                                   │
│ LDR Circuit                        │
│ ┌─────────────────┐               │
│ │ 3.3V ──────────┼─ 3.3V         │
│ │     ┌───┐     │               │
│ │     │LDR │     │               │
│ │     └───┘     │               │
│ │       │         │               │
│ │     ┌───┐     │               │
│ │     │10kΩ│     │               │
│ │     └───┘     │               │
│ │       │         │               │
│ │       └─────────┼─ D3           │
│ │                 │               │
│ │ GND ───────────┼─ GND          │
│ └─────────────────┘               │
│                                   │
│ LED Circuit                         │
│ ┌─────────────────┐               │
│ │ 3.3V ──────────┼─ 3.3V         │
│ │     ┌───┐     │               │
│ │     │220Ω│     │               │
│ │     └───┘     │               │
│ │       │         │               │
│ │     ┌───┐     │               │
│ │     │LED │     │               │
│ │     └───┘     │               │
│ │       │         │               │
│ │       └─────────┼─ D5           │
│ │                 │               │
│ │ GND ───────────┼─ GND          │
│ └─────────────────┘               │
└─────────────────────────────────────┘

Important Wiring Note

Pin Conflict Resolution: The rain sensor and battery monitoring both need analog input (A0). Solutions:

Option 1: Priority to Battery Monitoring

Rain Sensor: Use digital output instead of analog
- Connect rain sensor DO to D6 (if available)
- Use digital threshold detection
- A0 reserved for battery monitoring

Option 2: Analog Multiplexing

Use CD4051 analog multiplexer
- Connect multiple analog inputs to A0
- Switch between battery and rain sensor
- More complex but preserves both analog inputs

Option 3: Separate Battery Monitoring

Use dedicated battery monitoring IC
- MAX17043 or similar fuel gauge
- I2C communication instead of analog
- Frees up A0 for rain sensor

Recommended Solution: Digital Rain Sensor

Rain Sensor Digital Configuration
┌─────────────────┐
│ Rain Sensor     │
│ Module          │
│                 │
│ VCC ───────────┼─ 3.3V
│ GND ───────────┼─ GND
│ DO ────────────┼─ D6 (GPIO12)
│ AO ────────────┼─ (Not used)
└─────────────────┘

Power Management Features

Battery Protection

• Overcharge protection (4.2V cutoff)
• Over-discharge protection (2.5V cutoff)
• Short circuit protection
• Temperature protection

Solar Charging

• Maximum power point tracking (MPPT) optional
• Reverse polarity protection
• Charging status indicators

Power Optimization

• Deep sleep capability
• Battery level monitoring
• Low power warnings
• Automatic shutdown on critical battery level

Assembly Instructions

Step 1: Battery System

1. Install 18650 in holder with protection circuit
2. Connect to TP4056 charging module
3. Test charging with USB power
4. Verify protection circuit operation

Step 2: Solar Integration

1. Connect solar panel to TP4056 input
2. Install Schottky diode for reverse protection
3. Test solar charging in direct sunlight
4. Verify charging LED indicators

Step 3: Power Regulation

1. Connect battery output to 3.3V buck converter
2. Adjust output to 3.3V
3. Test with full load (all sensors active)
4. Verify efficiency (>90%)

Step 4: Battery Monitoring

1. Build voltage divider (100kΩ + 100kΩ)
2. Connect to A0 pin
3. Calibrate with known voltage
4. Test accuracy

Step 5: Weather Station Assembly

1. Connect all sensors to Wemos D1 Mini
2. Use digital rain sensor (D6) to free A0
3. Connect power from buck converter
4. Test complete system

Expected Performance

Solar Charging (6V 2W Panel)

• Peak Current: ~333mA @ 6V
• Daily Energy: ~2Wh (sunny day)
• Charging Time: 4-6 hours (full charge)

Battery Runtime

• Active Mode: ~15 hours (2500mAh ÷ 160mA)
• Deep Sleep: ~125,000 hours (theoretical)
• Mixed Operation: Several days with solar support

System autonomy

• Sunny Location: 100% solar powered
• Cloudy Location: Battery supplementation needed
• Night Operation: Battery powered only

Troubleshooting

Common Issues

• No Charging: Check solar panel orientation and connections
• Low Battery: Insufficient solar panel size
• Inaccurate Reading: Calibrate voltage divider
• System Resets: Check power supply stability

Testing Procedures

1. Solar Output: Measure voltage and current in sunlight
2. Charging Current: Monitor battery charging rate
3. System Load: Measure total current consumption
4. Battery Life: Test runtime without solar input

This solar-powered system enables truly autonomous weather station operation with minimal maintenance requirements.