Decade Counter

Mr BILLINGTON

Component Theory - Decade Counter

The 4017b Decade Counter is part of the 4000 CMOS Logic family of integrated circuits. It is a 16 pin DIL IC that has 10 primary outputs. Each output is triggered in order from 0-9 when a complete digital pulse (0,1) is received at the 'clock' input

Pins 1 to 7 and pin 9 and pin 11 are outputs for the counter (3V)
Pin 8 is the negative power supply
Pin 12 is the carry-out pin, '÷ 10 output' to connect to another 4017
Pin 13 is the enable pin. It can be used to stop the count (held LOW)
Pin 14 is the clock pin. This is the input pin for the digital pulse
Pin 15 is the reset pin. This returns counter to zero
Pin 16 is the positive power supply pin. It runs at a voltage between 3V and 16V

The 'Divide by 10' output or carry out is technically the 11th output despite the name 'Decade' counter. This output is HIGH for half the output cycle (0-4) and LOW for half the time (5-9). This can be used to create a further level of timing as the pulse can be connected to another 4017b which would trigger every time the first has made a complete cycle

The decade counter can be interfaced with other IC's or PIC's that can produce a logic signal (0,1). In this circuit a 555 timer has been used in astablemode to produce a continuous pulse to the 'clock' input of the decade counter. A second decade counter has been added which will count each complete output cycle (0-9).

Each 4017b output produces 3.5V (supply 6V) to the connected components which is why a resistor is not required for the LED's. If a transistor is used to interface with a 1K resistor is required to protect the base leg. If a higher supply voltage is used resistors will be required