# Wemos D1 Mini Weather Station Power Analysis

## Power Consumption Analysis

### Component Power Requirements

#### Wemos D1 Mini Development Board
- **Active Mode**: 70-200mA (typical 150mA)
- **WiFi Transmission**: 150-200mA peaks
- **Deep Sleep Mode**: 10-20µA
- **Modem Sleep**: 80mA
- **Operating Voltage**: 3.3V
- **Power**: ~0.5W (active), ~0.66W (WiFi peak)

#### Sensors
- **DHT11**: 1.5mA (measurement), 40µA (standby)
- **BMP180**: 1mA (measurement), 5µA (standby)
- **Rain Sensor Module**: 3-5mA (continuous)
- **LDR Circuit**: ~0.3mA (with 10kΩ pull-down)

#### LED Indicator
- **LED**: 20mA (full brightness)
- **With 220Ω resistor**: ~15mA @ 3.3V

#### Battery Monitoring
- **Voltage Divider**: ~0.1mA (100kΩ + 100kΩ)
- **ADC Reading**: Minimal additional current

### Total Power Consumption

#### Active Operation (WiFi + All Sensors)
```
Wemos D1 Mini (active): 150mA
WiFi transmission:     200mA (peaks)
DHT11:                 1.5mA
BMP180:                1mA
Rain Sensor:           5mA
LDR Circuit:           0.3mA
LED:                   15mA
Battery Monitor:       0.1mA
---------------------------
Total (typical):       ~172mA
Total (peak):          ~222mA
```

#### Low Power Operation (WiFi Sleep)
```
Wemos D1 Mini (modem sleep): 80mA
DHT11 (standby):              0.04mA
BMP180 (standby):             0.005mA
Rain Sensor:                  5mA
LDR Circuit:                  0.3mA
LED (off):                    0mA
Battery Monitor:              0.1mA
-------------------------------
Total:                        ~85mA
```

#### Deep Sleep Mode
```
Wemos D1 Mini (deep sleep): 0.02mA
DHT11 (standby):             0.04mA
BMP180 (standby):            0.005mA
Rain Sensor:                0mA (if powered down)
LDR Circuit:                 0mA
LED (off):                   0mA
Battery Monitor:             0.1mA
-------------------------------
Total:                       ~0.165mA
```

## 18650 Battery Analysis

### 18650 Battery Specifications
- **Capacity**: 2000-3500mAh (typical 2500mAh)
- **Voltage**: 3.7V (nominal), 4.2V (full), 2.5V (empty)
- **Energy**: ~9.25Wh (2500mAh × 3.7V)
- **Discharge Rate**: 1C-2C typical (2.5A-5A for 2500mAh)

### Runtime Calculations

#### Scenario 1: Continuous Active Operation
- **Current Draw**: 172mA @ 3.7V
- **Battery Capacity**: 2500mAh
- **Runtime**: 2500mAh ÷ 172mA = **14.5 hours**

#### Scenario 2: Intermittent Operation (Normal Use)
- **Active (30%)**: 172mA × 0.3 = 51.6mA average
- **Low Power (70%)**: 85mA × 0.7 = 59.5mA average
- **Total Average**: 111.1mA
- **Runtime**: 2500mAh ÷ 111.1mA = **22.5 hours**

#### Scenario 3: Deep Sleep Strategy
- **Active (5%)**: 172mA × 0.05 = 8.6mA
- **Deep Sleep (95%)**: 0.165mA × 0.95 = 0.157mA
- **Total Average**: 8.76mA
- **Runtime**: 2500mAh ÷ 8.76mA = **285 hours (11.9 days)**

#### Scenario 4: Optimized Operation
- **Active (10%)**: 172mA × 0.1 = 17.2mA
- **Moderate Sleep (90%)**: 80mA × 0.9 = 72mA
- **Total Average**: 89.2mA
- **Runtime**: 2500mAh ÷ 89.2mA = **28.0 hours**

#### Scenario 5: Solar-Assisted Operation
- **Active (30%)**: 172mA × 0.3 = 51.6mA average
- **Low Power (70%)**: 85mA × 0.7 = 59.5mA average
- **Total Average**: 111.1mA
- **Solar Input**: 6V 2W panel provides ~333mA @ 3.3V
- **Net Consumption**: 111.1mA - 333mA = -222mA (charging)
- **Runtime**: **Continuous operation with battery charging**

## Power Management Recommendations

### Voltage Regulation
Since Wemos D1 Mini and sensors operate at 3.3V, but 18650 provides 3.7V:

```
18650 (3.7V) → DC-DC Buck Converter → 3.3V
```

**Required Converter Specifications:**
- **Input Voltage**: 2.5V-4.2V
- **Output Voltage**: 3.3V
- **Efficiency**: >90%
- **Max Current**: >200mA (Wemos D1 Mini requirement)
- **Recommended**: TP4056 with protection + 3.3V buck converter

### Power Management Strategies

#### 1. WiFi Sleep Mode
```cpp
// Enable WiFi sleep between transmissions
WiFi.setSleep(true);
```

#### 2. Deep Sleep with Timer
```cpp
// Sleep for 5 minutes between readings
ESP.deepSleep(5 * 60 * 1000000); // Wemos D1 Mini
```

#### 3. Sensor Power Management
```cpp
// Power down sensors when not reading
digitalWrite(SENSOR_POWER_PIN, LOW);
```

#### 4. LED Power Management
```cpp
// Turn off LED when not needed
digitalWrite(LED_PIN, LOW);
```

### Battery Monitoring

#### Voltage Monitoring
```cpp
// Monitor battery voltage (Wemos D1 Mini - 10-bit ADC)
float batteryVoltage = analogRead(BATTERY_PIN) * (3.3 / 1023.0) * 2.0; // Voltage divider
if (batteryVoltage < 3.0) {
  // Low battery warning
}
```

#### Battery Percentage
```cpp
int batteryPercentage = map(batteryVoltage, 3.0, 4.2, 0, 100);
```

## Power Optimization Code

### Optimized Loop Structure
```cpp
void loop() {
  // Wake up sensors
  digitalWrite(SENSOR_POWER_PIN, HIGH);
  delay(100);
  
  // Read sensors
  readSensors();
  
  // Update display briefly
  updateDisplay();
  
  // Send MQTT data
  sendMQTTData();
  
  // Power down sensors
  digitalWrite(SENSOR_POWER_PIN, LOW);
  lcd.noBacklight();
  
  // Sleep for extended period
  esp_sleep_enable_timer_wakeup(300000000); // 5 minutes
  esp_deep_sleep_start();
}
```

### Battery-Powered Configuration
```cpp
// Power saving settings (Wemos D1 Mini)
WiFi.setSleep(true);
WiFi.setSleepMode(WIFI_LIGHT_SLEEP);
```

## Recommendations

### For Single 18650 Operation:
1. **Use Deep Sleep**: Essential for multi-day operation
2. **Optimize Reading Frequency**: 5-15 minute intervals
3. **Power Down Sensors**: Cut power when not reading
4. **Use Efficient Voltage Regulation**: Buck converter >90% efficiency
5. **Monitor Battery Voltage**: Prevent over-discharge

### Expected Runtime with Optimization:
- **Conservative**: 7-10 days (5-minute readings)
- **Aggressive**: 14-21 days (15-minute readings)
- **Minimal**: 28+ days (30-minute readings)
- **Solar-Assisted**: Continuous operation with battery charging

### Hardware Requirements:
- 18650 battery (2500mAh+ recommended)
- Battery holder with protection circuit
- 3.3V buck converter (high efficiency)
- Battery voltage divider for monitoring
- 6V 2W solar panel for continuous operation

## Power Consumption Comparison

### ESP32 vs Wemos D1 Mini
| Feature | ESP32 | Wemos D1 Mini | Improvement |
|---------|-------|---------------|-------------|
| **Active Current** | 200mA | 150mA | 25% less |
| **WiFi Peak** | 250mA | 200mA | 20% less |
| **Deep Sleep** | 0.01mA | 0.02mA | Similar |
| **Battery Runtime** | 5.3 hours | 14.5 hours | 174% better |
| **Deep Sleep Runtime** | 105 hours | 285 hours | 171% better |

### Solar Panel Requirements
- **ESP32 System**: 6V 3W panel recommended
- **Wemos D1 Mini System**: 6V 2W panel sufficient
- **Power Margin**: Wemos D1 Mini has 33% more solar margin

## Conclusion

**Yes, one 18650 can run this system exceptionally well**, with significant advantages:

- **Continuous Operation**: 14.5 hours (practical for daily use)
- **Optimized Operation**: 7-21 days (with deep sleep)
- **Solar-Assisted**: Continuous operation with battery charging
- **Key Advantage**: Wemos D1 Mini's lower power consumption
- **Voltage Regulation**: Proper 3.3V regulation needed
- **Battery Protection**: Prevent over-discharge below 3.0V

The Wemos D1 Mini provides superior battery life compared to ESP32, making it ideal for battery-powered weather station applications. With solar panel integration, truly autonomous operation is achievable.