CD4017 or HCF4017BE or 74HC4017 is a 16 pin CMOS decade counter/ Divider with 10 decoded output. This is known as ‘Johnson 10 stage decade counter’. It has 10 outputs which gives output signal one by one in sequence when a clock signal from the clock input given. When clock input given ,turns on the 10 output in sequence at each time when it receives clock input pulses.
CD4017 is most popular ic which is extremely useful in various applications like Binary counter,Decoder,Decade counter,Frequency division etc . This is more useful in various projects like Light Chaser, Remote controlled Switch, Alarm,Touch ON OFF switch, Clap switch, Matrix Die.
This IC is also used in electronic industries, automotive industries, manufacturing medical electronic devices, alarms and in electronic instrumentation device.
Clock pin (pin14)- This is the input pin which gets the input clock signal from external circuitry. Whenever pin 14 goes high, it provides the output. For first clock pulse pin 3 will provide output; for next pulse pin 2 will provide output and after from pin 4 and so on. After 10 pulse it will again start from Q0 output.
Reset pin (pin 15) – It is used to reset the counter to zero. This is used to reset the IC . The function of this pin is to revert the sequence back to the initial state. When a positive signal or supply voltage applied at this pin, the sequencing comes back to pin 3 and begins the cycle .
If the positive supply is held connected to this pin 15, output goes and holds to the pin 3 (output First) and making this pinout high and fixed.
Therefore to make the IC function Enable, pin 15 should always be connected to ground
.Clock Inhibit pin (pin 13)- It is used to switch the counter “on” and “off”. When we want to switch off the counter, then pin 13 should be high. This pin is used to enable the ic to provide outputs high sequence wise. IC is ON (Enable )with negative signal on this pin. Pin 13 may be considered as the opposite of pin 14 and this pin out respond to negative peak signals.
In case pin 13 is connected to positive, the whole IC will stops and the outputs will stop sequencing and stop responding to any clock signal applied at pin 14. It will ignore the clock pulse no matter how many times you press the switch meaning the counter will not advance.
Output pin (pin Q0- Q9)- Pin no 1-7 and 9-11 are the output pins . It is used to receive the output in sequential manner. Like for first pulse pin 3 will provide the output and then pin 2 , then pin 4 and so on. All output pins provide output one by one.
Ground pin (pin 8)- This pin is ground pin and must connected with negative supply.
VCC (pin 16)– It is connected with positive vcc supply
Carry out pin (pin 12)– When we need to connect more than one ic then It is used to connect one or more CD4017 IC’s. The carry pin of first CD4017 is connected to clock input of second and the carry pin of second is connected to the clock input of third and so on.
It is used when we needs to connect two or more ic in cascade. It completes one full cycle for every 10 clock cycles. Next this output is shifted to its next output pin and this sequence continues till the next clock cycle.
By cascading with another 4017 IC, we can count up to 20 numbers. We can increase and increase the range of counting by cascading it with more and more IC 4017s. Each additional cascaded IC will increase the counting range by 10.
This is the circuit diagram of LED flasher using 4017 which all 10 outputs High (ON) one by one as getting clock signal at pin 14 through the 555 timer ic. At each positive clock pulse output goes to next and previous are off accordingly. By the given below animation diagram it is more clear to understand.