A quick course in Binary

project #16: creating an led Binary number display

In this project, we’ll use eight LEDs to display binary numbers from 0 to 255. Our sketch will use a for loop to count from 0 to 255 and will send each value to the shift register, which will use LEDs to display the binary equivalent of each number.

The Hardware

The following hardware is required:

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  One 74HC595 shift register IC
  
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  Eight LEDs (LED1 to LED8)
  
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  Eight 560 W resistors (R1 to R8)
  
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  One breadboard
  
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  Various connecting wires
  
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  Arduino and USB cable
  

Connecting the 74HC595

Figure 6-5 shows the schematic symbol for the 74HC595.

74HC595

Figure 6-5: 74HC595 schematic symbol
There are 16 pins on our shift register:

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  Pins 15 and 1 to 7 are the eight output pins that we control (labeled Q0 to Q7, respectively).
  
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  Q7 outputs the first bit sent to the shift register, down to Q0, which outputs the last.
  
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  Pin 8 connects to GND.
  
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  Pin 9 is “data out” and is used to send data to another shift register if one is present.
  
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  Pin 10 is always connected to 5 V (for example, the 5 V connector on the Arduino).
  
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  Pins 11 and 12 are called clock and latch.
  
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  Pin 13 is called output enable and is usually connected to GND.
  
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  Pin 14 is for incoming bit data sent from the Arduino.
  
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  Pin 16 is used for power: 5 V from the Arduino.
  

To give you a sense of the way pins are oriented, the semicircular notch on the left end of the body of the shift register IC shown in Figure 6-4 lies between pins 1 and 16.
The pins are numbered sequentially around the body in a counterclockwise direction, as shown in Figure 6-6, the schematic for our LED binary number display.

note Once you have finished with this example circuit, keep it assembled. We’ll use it again with the forthcoming project.