Circuit Documentation

Summary

The circuit is designed to monitor the voltage of two 12v batteries and switch between them based on a voltage threshold using a microcontroller and relay system. The circuit includes voltage sensors to monitor the battery voltages, step-down power converters to provide 5v power to the microcontroller and relays, and a DC motor as the load. The ESP32 microcontroller reads the voltage levels from the sensors and controls the relays to switch the battery connection to the motor.

Component List

12v Battery

• Description: A 12v power source.
• Pins: - (Negative), + (Positive)

Voltage Sensor

• Description: Measures the voltage level of a circuit.
• Pins: Ground, Phase, Vcc, Out, Gnd

12v to 5v Step Down Power Converter

• Description: Converts 12v to a stable 5v output.
• Pins: VIN 9v-36v, VIN+, VIN-, USB OUTPUT 5V, 5v OUTPUT, GND

Relay 4 Channel 5v

• Description: A 4-channel relay module that can control up to four circuits.
• Pins: GND, IN1, IN2, IN3, IN4, VCC, COM1, COM2, COM3, COM4, NO1, NO2, NO3, NO4, NC1, NC2, NC3, NC4

ESP32 38 PINS

• Description: A microcontroller with WiFi and Bluetooth capabilities.
• Pins: GND, G23, G22, TXD, RXD, G21, G19, G18, G5, G17, G16, G4, G0, G2, G15, SDI, SD0, CLK, 3V3, EN, SP, SN, G34, G35, G32, 33, G25, G26, G27, G14, G12, G13, SD2, SD3, 5V

DC Motor

• Description: A motor that operates on DC power.
• Pins: pin 1, pin 2

Wiring Details

12v Battery

• - (Negative) connected to the negative input of the step-down converters and ground of the voltage sensors.
• + (Positive) connected to the positive input of the step-down converters and phase of the voltage sensors.

Voltage Sensor

• Ground connected to the negative terminal of the battery.
• Phase connected to the positive terminal of the battery.
• Vcc connected to the 5v output from the step-down converter.
• Out connected to the ESP32 for voltage sensing.
• Gnd connected to the ground of the circuit.

12v to 5v Step Down Power Converter

• VIN 9v-36v connected to the 12v battery.
• VIN+ connected to the positive terminal of the battery.
• VIN- connected to the negative terminal of the battery.
• USB OUTPUT 5V not used in this circuit.
• 5v OUTPUT connected to the Vcc of the voltage sensors, VCC of the relay module, and 5V of the ESP32.
• GND connected to the ground of the circuit.

Relay 4 Channel 5v

• GND connected to the ground of the circuit.
• IN1, IN2 controlled by the ESP32.
• VCC connected to the 5v output from the step-down converter.
• COM1 connected to the 5v output from the second step-down converter.
• NO1 connected to the DC motor.

ESP32 38 PINS

• 5V connected to the 5v output from the step-down converter.
• GND connected to the ground of the circuit.
• G34, G35 connected to the output of the voltage sensors.
• G23, G22 connected to the input of the relay module.

DC Motor

• pin 1 connected to the ground of the circuit.
• pin 2 connected to the normally open (NO) contact of the relay.

Documented Code

// Pin Definitions
const int sensorPin1 = 34; // Voltage Sensor 1 connected to G34
const int sensorPin2 = 35; // Voltage Sensor 2 connected to G35
const int relayPin1 = 23;  // Relay 1 IN1 connected to G23
const int relayPin2 = 22;  // Relay 2 IN2 connected to G22

// Voltage Threshold
const float voltageThreshold = 11.0; // Threshold voltage in volts

// Calibration Constants (to convert ADC value to voltage)
const float referenceVoltage = 3.3;  // Reference voltage of ESP32 ADC
const int adcMaxValue = 4095;        // Maximum ADC value (12-bit ADC)
const float voltageDividerRatio = 5.0; // Voltage divider ratio of the sensor

void setup() {
  // Initialize Serial Monitor for debugging
  Serial.begin(115200);

  // Initialize relay pins as outputs
  pinMode(relayPin1, OUTPUT);
  pinMode(relayPin2, OUTPUT);

  // Initially, connect Battery 1 to the load and disconnect Battery 2
  digitalWrite(relayPin1, LOW); // LOW means Relay 1 is connected
  digitalWrite(relayPin2, HIGH); // HIGH means Relay 2 is disconnected
}

void loop() {
  // Read the voltage from the sensors
  float voltage1 = readVoltage(sensorPin1);
  float voltage2 = readVoltage(sensorPin2);

  // Print the voltage values for debugging
  Serial.print("Battery 1 Voltage: ");
  Serial.print(voltage1);
  Serial.println(" V");
  
  Serial.print("Battery 2 Voltage: ");
  Serial.print(voltage2);
  Serial.println(" V");

  // Check if Battery 1 voltage drops below the threshold
  if (voltage1 < voltageThreshold) {
    // Switch to Battery 2
    digitalWrite(relayPin1, HIGH);  // Disconnect Battery 1
    digitalWrite(relayPin2, LOW);   // Connect Battery 2
    Serial.println("Switching to Battery 2...");
  } else {
    // Keep using Battery 1
    digitalWrite(relayPin1, LOW);   // Connect Battery 1
    digitalWrite(relayPin2, HIGH);  // Disconnect Battery 2
    Serial.println("Using Battery 1...");
  }

  // Delay for stability (adjust as needed)
  delay(1000);
}

// Function to read and convert ADC value to voltage
float readVoltage(int sensorPin) {
  int adcValue = analogRead(sensorPin);
  float voltage = (adcValue * referenceVoltage / adcMaxValue) * voltageDividerRatio;
  return voltage;
}

This code is designed to run on an ESP32 microcontroller. It initializes the relay pins and sets up the serial communication for debugging. The loop function reads the voltage from two sensors and switches the relays based on the voltage threshold. The readVoltage function converts the ADC value to a voltage reading, taking into account the reference voltage, ADC resolution, and voltage divider ratio.