Estiak Khan

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RODNEY THAYER

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Components

	Arduino UNO Microcontroller Module, release 3	x 1
	L7805	x 1
	SRD-05VDC-SL-C Songle Relay	x 1
	BC547(RANGE:420-800)	x 1
	1N4007	x 1

Tools, APP Software Used etc.

arduino IDE

Arduino

Description

DIY Easily Make a Universal Any Type of Battery Charge Controller At Home

DIY Easily Make a Universal Any Type of Battery Charge Controller At Home

If you’re into DIY electronics or renewable energy projects, you’ve probably faced the challenge of managing battery charging effectively. Building a universal battery charge controller at home is a cost-effective and rewarding solution. In this guide, we’ll show you how to construct your own battery charge controller using the ATmega328P IC and a few basic components. This controller works with multiple battery types, offering you flexibility and control.

Why Build a Universal Battery Charge Controller?

Cost-Efficiency: Commercial charge controllers can be expensive. DIY options save money.

Customizable: Tailor the controller to your specific needs.

Learning Opportunity: A perfect project to enhance your electronics skills.

How It Works

The ATmega328P microcontroller acts as the heart of this charge controller. It monitors the battery’s voltage using a voltage divider circuit connected to the A0 pin and controls charging using a relay connected to the D12 pin. Here's the step-by-step breakdown:

Voltage Monitoring:

The voltage divider scales down the battery’s voltage to a level readable by the ATmega328P (0-5V range).
The microcontroller reads this value through the A0 analog input.

Relay Control:

When the battery voltage is below a predefined threshold, the relay (connected to D12) activates, starting the charging process.
Once the battery reaches the desired voltage, the relay is turned off, stopping the charge to prevent overcharging.

Clock Stabilization:

The 16MHz crystal oscillator ensures accurate timing for the ATmega328P’s operations, stabilized by the 22pF capacitors.

Main Sections of the Circuit

Power Supply Regulation:

DC Input (DC1): The circuit is powered by an external DC source. The input voltage is regulated to a stable 5V for the ATmega328P and other components using the 7805 voltage regulator (U2).

Components for Regulation:

R1, R2: These resistors may be part of a voltage divider or used for a pull-down function.

C3, C2 (100pF): Capacitors for noise filtering and stability in the power supply.

X2 (12MHz Crystal Oscillator): Provides a clock signal for the ATmega328P, stabilized by the capacitors.

Microcontroller Unit (ATmega328P):

Microcontroller (U1): The ATmega328P is the core of this circuit, controlling the relay and monitoring inputs.

The clock signal for the microcontroller is provided by the 12MHz crystal oscillator (X2) with the 100pF capacitors acting as stabilizers.

Power supply pins for the microcontroller are connected to the regulated 5V output from the 7805.

Relay Control:

Relay Module (LOAD1): A single-channel relay is connected to the load. The relay allows the microcontroller to switch high-power devices on and off.

Q2 (BC547): A general-purpose NPN transistor is used to drive the relay. The base of the transistor is connected to the microcontroller's output pin via a current-limiting resistor (R10 = 1kΩ). The transistor acts as a switch, controlling the relay coil.

D2 (1N4007 Diode): This flyback diode protects the circuit from voltage spikes generated when the relay coil is de-energized.

R3 (10kΩ): This pull-down resistor ensures the transistor stays off when no signal is applied.

Relay Activation Control:

The ATmega328P controls the relay via one of its digital output pins (likely D12 or equivalent based on the connected pin in your code).
When the microcontroller sends a HIGH signal, the transistor (Q2) switches on, energizing the relay coil and allowing current to flow to the connected load.

Key Functionalities

Relay Operation:

The microcontroller monitors an input (like voltage or user command) and activates the relay based on programmed conditions.

For instance, if the input voltage (measured via a voltage divider circuit on an analog pin) is below or above certain thresholds, the microcontroller will toggle the relay.

Voltage Regulation:

The 7805 voltage regulator ensures a stable 5V supply for sensitive components like the microcontroller and logic circuits.

Relay Protection:

The 1N4007 diode prevents back EMF from damaging the transistor or microcontroller.

Tips for Success

Ensure proper heat dissipation for the relay if handling high currents.
Use fuses or protection circuits to safeguard against overcurrent or short circuits.
Test the circuit on a breadboard before soldering onto a PCB.

Applications

Solar charging systems.
Portable battery pack projects.
DIY power banks or UPS systems.

Video Reference

Conclusion

Building a universal battery charge controller using the ATmega328P is not only a great DIY project but also a practical tool for managing batteries effectively. With just a handful of components and some programming, you can create a versatile device suitable for multiple applications. Start today, and take your DIY skills to the next level!

Let us know your thoughts or questions in the comments. Don’t forget to share your results if you try this project!

Code

Autocu_single_relay.ino

Arduino

// Pin configuration
const int relayPin = 12;  // Relay control pin
const int voltageSensePin = A0;  // Voltage sensing pin

// Battery voltage limits
const float batteryFullVoltage = 14.4;  // Full cutoff voltage
const float batteryLowVoltage = 10.8;  // Low charging start voltage

// Voltage divider configuration
const float R1 = 10000.0;  // Resistor R1 value in ohms (10kΩ)
const float R2 = 3300.0;   // Resistor R2 value in ohms (3.3kΩ)

// ADC reference voltage
const float adcRefVoltage = 5.0;  // Reference voltage for the ADC
const int adcResolution = 1023;  // 10-bit ADC resolution

void setup() {
  pinMode(relayPin, OUTPUT);  // Set relay pin as output
  digitalWrite(relayPin, LOW);  // Turn off the relay initially
}

void loop() {
  // Read the ADC value
  int adcValue = analogRead(voltageSensePin);
  
  // Calculate the battery voltage using the voltage divider formula
  float batteryVoltage = (adcValue * adcRefVoltage / adcResolution) * ((R1 + R2) / R2);
  
  // Battery charging logic
  if (batteryVoltage >= batteryFullVoltage) {
    digitalWrite(relayPin, LOW);  // Turn off charging
  } else if (batteryVoltage <= batteryLowVoltage) {
    digitalWrite(relayPin, HIGH);  // Turn on charging
  }

  delay(1000);  // Delay for 1 second
}

Schematic and Layout

SCH_single-channel-Relay-with-ATmega328p_2024-11-27.json

Schematic_single-channel-Relay-with-ATmega328p_2024-11-27.png

Download Gerbers Download BOM(Bill of materials)

Nov 27,2024

114 views

DIY Easily Make a Universal Any Type of Battery Charge Controller At Home

If you’re into DIY electronics or renewable energy projects, you’ve probably faced the challenge of managing battery charging effectively.

114

Published: Nov 27,2024

Download Gerber file 4

BOM(Bill of materials)

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