How to Use 74HC4017: Examples, Pinouts, and Specs

The 74HC4017 is a high-speed CMOS device that serves as a 5-stage Johnson decade counter with 10 decoded outputs. It is designed to produce a sequence of output pulses, one at a time, for every input pulse received. This component is widely used in digital logic circuits for creating LED chasers, frequency dividers, and various timing and counting applications.

• LED chaser circuits
• Frequency division
• Digital counters
• Sequential logic operations
• Signal decoding

• Supply Voltage (Vcc): 2V to 6V
• Input Voltage (Vin): -0.5V to Vcc + 0.5V
• Output Current (Iout): 25mA per output
• Clock Frequency (fclk): Up to 25MHz (Vcc = 6V)
• Operating Temperature: -40°C to +125°C

1. Power Supply: Connect Vcc to a positive supply voltage (2V to 6V) and GND to the circuit ground.
2. Clock Input: Apply a clock signal to the CLOCK pin. The counter advances on the rising edge of the clock.
3. Reset: Connect the MR pin to a logic high to reset the counter to zero.
4. Clock Inhibit: Apply a logic high to the CLOCK INHIBIT pin to stop the counter from advancing.
5. Outputs: Connect the Q0 to Q9 outputs to the devices you wish to control sequentially.
6. Cascading: Use the CO pin to cascade multiple 74HC4017 chips for more than 10 decoded outputs.

• Ensure that the supply voltage does not exceed the maximum rating to prevent damage.
• Use a pull-down resistor on the MR pin to prevent accidental resets due to noise.
• Decouple the power supply with a 0.1µF capacitor close to the Vcc pin to filter out noise.
• Avoid floating inputs by connecting unused pins to an appropriate logic level.

// Define the output pins connected to the 74HC4017
int outputs[] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11};

void setup() {
  // Set all the output pins as outputs
  for (int i = 0; i < 10; i++) {
    pinMode(outputs[i], OUTPUT);
  }
  // Set the clock pin as output
  pinMode(12, OUTPUT);
}

void loop() {
  // Send a clock pulse to the 74HC4017
  digitalWrite(12, HIGH);
  delay(10); // Short delay to ensure the clock pulse is registered
  digitalWrite(12, LOW);
  delay(500); // Delay between each pulse to control the speed of the LED chaser
}

• LEDs are not lighting up in sequence: Check the clock signal and ensure it is connected properly and has a clean rising edge.
• Counter resets unexpectedly: Verify that the MR pin is not floating and is connected to a stable logic level.
• Counter skips outputs: Ensure that the CLOCK INHIBIT pin is not accidentally activated.

• Use an oscilloscope to check the clock signal integrity.
• Add a pull-down resistor to the MR pin to keep it at a logic low when not in use.
• Check for solder bridges or shorts that may cause unintended behavior.

Q: Can I use the 74HC4017 at a voltage lower than 2V? A: No, the device is not guaranteed to function correctly below its minimum rated supply voltage.

Q: How can I increase the number of outputs beyond 10? A: You can cascade multiple 74HC4017 counters by connecting the CO pin of the first to the CLOCK pin of the next.

Q: Is it necessary to use all the outputs? A: No, you can leave unused outputs unconnected. However, it is good practice to ensure they are not floating.

Q: Can the 74HC4017 be used with an Arduino? A: Yes, the 74HC4017 can be easily interfaced with an Arduino or any other microcontroller platform.