7-segment display

Posted on Feb 7, 2014

This experiment is more of an introduction to the 4511 decoder/display driver IC than it is a lesson in how to `build up` a digital function from lower-level components. Since 7-segment displays are very common components of digital devices, it is good to be familiar with the `driving` circuits behind them, and the 4511 is a good example of a typi

cal driver IC. Its operating principle is to input a four-bit BCD (Binary-Coded Decimal) value, and energize the proper output lines to form the corresponding decimal digit on the 7-segment LED display. The BCD inputs are designated A, B, C, and D in order from least-significant to most-significant. Outputs are labeled a, b, c, d, e, f, and g, each letter corresponding to a standardized segment designation for 7-segment displays. Of course, since each LED segment requires its own dropping resistor, we must use seven 470 © resistors placed in series between the 4511`s output terminals and the corresponding terminals of the display unit. Most 7-segment displays also provide for a decimal point (sometimes two!), a separate LED and terminal designated for its operation. All LEDs inside the display unit are made common to each other on one side, either cathode or anode. The 4511 display driver IC requires a common-cathode 7-segment display unit, and so that is what is used here. After building the circuit and applying power, operate the four switches in a binary counting sequence (0000 to 1111), noting the 7-segment display. A 0000 input should result in a decimal "0" display, a 0001 input should result in a decimal "1" display, and so on through 1001 (decimal "9"). What happens for the binary numbers 1010 (10) through 1111 (15) Read the datasheet on the 4511 IC and see what the manufacturer specifies for operation above an...

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