Counter circuits

Counter circuits record the number of times an event takes place.

The counter circuit you are most likely to come across is the 4017 decade counter IC, which can be set to count to any value between one and 10 , over and over again. The 4017 is a complementary metal oxide semiconductor (CMOS) integrated circuit.

A decade counter has ten outputs. When it is turned on, the counter switches from one output to the next. The speed at which each output turns on or 'goes high' is determined by a timer connected to an input. The counter is switched on and off using either a manual switch or with an astable 555 timer (using pin 3 on the 555 as the output).

Below is a pin-out diagram showing the arrangement of pins in a 4017 counter chip, and a guide to what each pin does.

Pin-out diagram for a 4017 decade counter

Pins 1 to 7 and pin 9 and pin 11 are outputs for the counter.
Pin 8 is the negative power supply.
Pin 12 is the carry-out pin (this could be connected to another 4017).
Pin 13 is the enable pin. It can be used to stop the count.
Pin 14 is the clock pin. This will be connected to a manual switch or to an astable 555 timer.
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.

Random number generation

The circuit below shows a decade counter being used as a random number generator or electronic dice. The input 14 can be connected to a 555 timer to operate the dice. A switch has been connected to pin 13, which will stop the dice when pressed.