Understanding the CD4017 Decade Counter IC

The CD4017 is a versatile CMOS (Complementary Metal-Oxide-Semiconductor) integrated circuit (IC) primarily used as a decade counter or divider. As a member of the 4000 series of CMOS ICs, it’s appreciated for its low power consumption, wide operating voltage range, and overall versatility.

Let’s delve into the CD4017 decade counter circuit, exploring its pin diagram, specifications, and key features. Applications for the CD4017 include LED chasers, sequential LED displays, decade counters, frequency dividers, and a variety of timing and sequencing applications. Its simplicity, low power requirements, and frequency division capabilities make it a popular choice for digital electronics projects.

The CD4017 is specifically designed as a decade counter, meaning it counts in increments of ten, counting from 0 to 9 in binary-coded decimal (BCD) format.

Beyond its counting capabilities, the CD4017 can also function as a frequency divider. By connecting an external clock signal to the Clock (CLK) input pin, it divides the frequency of the input signal by 10 at the output.

CD4017 Pin Diagram

Here’s a look at the CD4017 pin diagram:

The CD4017 has 10 output pins (Q0-Q9), each representing one count in the decade sequence. These outputs are sequentially activated as the counter advances from one count to the next.

The following table outlines the pin details of the CD4017:

Key Pin Functions

• Reset Pin: The CD4017 features a Reset (RESET) pin. When pulled low (grounded), this pin resets the counter back to its initial state (count 0). This allows for manual or external control of the counter’s reset.
• Clock Input: The CLK input pin receives clock pulses, advancing the counter. Typically, an external clock signal is connected here, though it can also be driven by an oscillator or other timing circuit.
• Clock Enable: The CD4017 includes a Clock Enable (CE) pin. When held low, this pin disables the CLK input, preventing the counter from advancing. This offers external control over the counting operation.

Internally, the CD4017 includes decoding logic to determine which output pin is active based on the current count. As the counter progresses, the active output pin shifts to the next in the sequence.

Like most ICs, the CD4017 requires a stable power supply voltage, typically in the range of 3 to 15 volts.

CD4017 Decade Counter Circuit Example: LED Chaser

An LED chaser circuit using the CD4017 decade counter and NE555 timer is a simple yet visually appealing demonstration of sequential LED lighting effects.

The LED chaser circuit creates a visual effect where multiple LEDs turn on and off in a sequential pattern, giving the impression of lights chasing each other. It utilizes the CD4017, an NE555 timer, LEDs, and other components. The NE555 timer IC is configured in astable mode to generate clock pulses for the CD4017 counter.

Applications of CD4017

• Automotive
• Alarm systems
• Medical Electronics
• Instrumentation
• Remote metering
• Industrial electronics

Conclusion

The CD4017 decade counter is a versatile integrated circuit widely used in digital electronics projects. Its ability to sequentially activate output pins in response to clock pulses makes it suitable for various applications, including LED chasers, sequential LED displays, frequency dividers, and more.