Home > Circuit Bricks > Counter - 7 segment
UPDATED:.21:03 21 October 2013

FUNCTION BLOCK
DESCRIPTION
  • This circuit will count input pulses and display the count directly on a 7-segment display.
  • It's one IC with only output resistors for LEDs needed.
CIRCUIT DETAILS

The circuit is based around the very popular 4026 counter IC. It is a CMOS type and can work from a wide voltage range. The circuit shown will count input pulses. Leave inputs as they are if not using them.

It is a digital device and works with logic level inputs. A high refers to +v and low refers to 0v.

Inputs

Circuit Diagram
  • Clock - A high pulse on this input increments the count
  • Enable - A high input will stop the counting.
  • Reset - A high input will reset the counter to zero.
  • Display - A low input will blank out the display.

Outputs

The outputs must have resistors in series with the LEDs if using a standard seven segment display. (see below)

The type used must be a common cathode type, meaning all the cathodes are connected together.

The "Nxt Clk" provides a low-high pulse when it counts from 9 to 0. Connect this to the Clock of the next counter, if used.

MODIFICATION DETAILS

The circuit shown will produce a single digit display. Circuits can be cascaded (connected in series) to produce an unlimited number of multi-digit displays. The "10's Clk" output always connects to the next digit clock input.

Resistors R4-10 are important to regulate the current to the LED segments. The value depends on the voltage supply you are using. The value can be calculated using Ohms Law.
See Decoder, BCD-7 segment for details on calculating the resistor value for the output.

PACKAGE DETAILS
The 4026B counter comes in an 16pin DIL package. The pin connections are below.


Note: Clk En is active low.

If possible use an IC holder so the IC can be removed easily and is not damaged from excessive heat while soldering.
IMPORTANT: Try not to handle the pins of the IC too much. They do have protection diodes connected inside but CMOS types are very sensitive to static charge.
LINKS
Links to projects using the 4026B
...GCSE Projects/Pig Sentry

...Circuits/Single Digit Scoreboard

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Written by Phil Townshend - 2008
www.edutek.ltd.uk - Working Electronics For Students & Teachers