How to Use 7805: Examples, Pinouts, and Specs

The 7805 is a widely used linear voltage regulator that outputs a stable 5V DC from a higher input voltage, typically ranging from 7V to 35V. This component is essential in many electronic devices, ensuring that sensitive electronic circuits receive a constant voltage, which is crucial for reliable operation. Common applications include power supplies for microcontrollers, small motors, and other digital logic circuits.

• Output Voltage: 5V
• Input Voltage (recommended): 7V to 25V
• Input Voltage (maximum): 35V
• Output Current (maximum): 1A (with adequate heat sinking)
• Quiescent Current: 5mA (typical)
• Dropout Voltage: 2V (typical at full load)
• Short Circuit Protection: Yes
• Thermal Overload Protection: Yes
• Package: TO-220 (commonly used)

1. Connect the input voltage to pin 1 of the 7805. Ensure that the voltage is within the recommended range.
2. Connect pin 2 to the ground of your power source and the ground of your circuit.
3. Connect pin 3 to the power input of your 5V circuit.
4. It is recommended to place a 0.33uF ceramic capacitor between the input pin and ground to filter input noise.
5. Place a 0.1uF ceramic capacitor between the output pin and ground to improve transient response.

• Always use capacitors on the input and output as specified to minimize voltage fluctuations.
• Ensure the input voltage is always at least 2V greater than the output voltage to maintain regulation.
• Provide adequate heat sinking if the regulator is expected to handle currents near 1A, as it will dissipate heat.
• Avoid reverse polarity; it can damage the regulator.
• Keep the regulator away from high-frequency switching components to prevent interference.

• Voltage Drop: If the output voltage is lower than 5V, check the input voltage and ensure it is at least 2V above the desired output.
• Overheating: If the regulator is too hot, improve heat sinking or reduce the load current.
• No Output: Ensure the input is connected correctly and that there are no short circuits on the output.

Q: Can I use the 7805 without capacitors? A: It is not recommended as the capacitors help to maintain a stable output voltage and reduce noise.

Q: What is the maximum input voltage for the 7805? A: The absolute maximum input voltage is 35V, but it is recommended to keep it at 25V or below for reliable operation.

Q: How can I increase the output current? A: You can parallel multiple 7805 regulators with diodes on the outputs to prevent backfeeding, but this is not an ideal solution. Consider using a switching regulator for higher currents.

Q: Can the 7805 be used with an Arduino UNO? A: Yes, the 7805 can be used to provide a stable 5V supply to an Arduino UNO or any other microcontroller that operates at 5V.

// No specific code is required for using the 7805 with an Arduino UNO.
// Simply connect the 7805 regulated 5V output to the 5V pin on the Arduino,
// and the ground from the 7805 to the GND pin on the Arduino.

void setup() {
  // Initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  // Turn the LED on (HIGH is the voltage level)
  digitalWrite(LED_BUILTIN, HIGH);
  // Wait for a second
  delay(1000);
  // Turn the LED off by making the voltage LOW
  digitalWrite(LED_BUILTIN, LOW);
   // Wait for a second
  delay(1000);
}

Note: The above code is a simple blink program to test the functionality of the Arduino UNO when powered by the 7805 voltage regulator. The 7805 itself does not require any code to operate.