Seven Segment

A Seven Segment display is a package of 8 LED's with the layout of an 8 and a decimal point. Although a 'seven' segment, the decimal point can be used making it technically an eight. Each segment is independently controlled to form the numbers 0-9. They can be either Common Anode (shared positive) or Common Cathode (shared negative)

The Seven Segment is typically connected to a 4026bseven segment driver which converts each digital pulse at its 'clock' input to control the outputs in order to display each number in sequence. The 4026b will only count up from 0-9 on the display and not down.

The pin layout of the 4026b is as follows;

Pin 1 - Clock input pin, controls the timing of number changes
Pin 2 - Clock Enable, should be held LOW to count
Pin 3 - Enable Display, Typically held HIGH to turn display on
Pin 4 - Enable Out, held HIGH if connected to another 4026b
Pin 5 - 'Divide by 10', high half the cycle and low other half
Pin 6, 7, 9 - 13 - Seven Segment output pins typically 3V
Pin 14 - 2 Output, output HIGH when 2 is displayed
Pin 15 - Reset Pin, will reset the counter to 0 if HIGH
Pin 16 - Positive supply voltage (3-15V)

The circuit shows the typical design of a seven segment 4026b circuit. Current limiting resistors (220Ω) are used on each output to protect the LED segments. Further counting over 9 can be achieved by using the Q10 (÷10) output pin to connect to the clock of another 4026b. This will then add 10's, 100's, 1000's etc.

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Advantages of using a Seven Segment Display are;

Clear and recognisable number display
Saves space in a product compared to 8 LED's
Easier to assemble and solder than 8 LED's
Can count to any number when extended

Disadvantage of using a Seven Segment are;

Must be fixed to the PCB which limits case design
Standard size quite small and increases get costly
Dated aesthetic due to advancements in screen technology
Difficult to repair/de-solder if damaged

A 4017BDecade Counter is a 16 pin DIL IC that is part of the logic family of IC's the 4000 series. As the name suggests it has 10 primary outputs that are independently controlled in chronological order from 0- 9.

The Decade Counter is controlled by a Digital pulse to the 'Clock' input pin (14). Every complete pulse (0,1) it receives it triggers the next output in the sequence repeatedly.

Pins 1 - 7 & Pin 9 & Pin 11 are outputs
Pin 8 is the negative power supply.
Pin 12 is the carry-out pin ÷10 (can be connected to another 4017)
Pin 13 is the enable pin. Typically connected to ground (-)
Pin 14 is the clock pin. Responsible for timing
Pin 15 is the reset pin. This returns counter to zero.
Pin 16 is the positive power supply pin. Between 3V and 16V

The 'Divide by 10' output on pin 12 is actually the 11th output on the decade counter. This however is on for half of the output cycle (0-4) and off for the other half (5-9). For this reason it can be used to output to another 4017b or other IC to indicate when a complete output cycle has occurred.

Component Theory - Seven Segment Display

Mr BILLINGTON

The Decade Counter is controlled by a Digital pulse to the 'Clock' input pin (14). Every complete pulse (0,1) it receives it triggers the next output in the sequence repeatedly.

Pins 1 - 7 & Pin 9 & Pin 11 are outputs
Pin 8 is the negative power supply.
Pin 12 is the carry-out pin ÷10 (can be connected to another 4017)
Pin 13 is the enable pin. Typically connected to ground (-)
Pin 14 is the clock pin. Responsible for timing
Pin 15 is the reset pin. This returns counter to zero.
Pin 16 is the positive power supply pin. Between 3V and 16V