The 4511 IC is built to recognize this, and output (or not output!) accordingly. These are binary values beyond the range of a single decimal digit, and so have no function in a BCD system. 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 input value of 9.

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”). The 4511 display driver IC requires a common-cathode 7-segment display unit, and so that is what is used here.Īfter building the circuit and applying power, operate the four switches in a binary counting sequence (0000 to 1111), noting the 7-segment display. All LEDs inside the display unit are made common to each other on one side, either cathode or anode. Most 7-segment displays also provide for a decimal point (sometimes two!), a separate LED and terminal designated for its operation. Of course, since each LED segment requires its own dropping resistor, we must use seven 470 Ω resistors placed in series between the 4511’s output terminals and the corresponding terminals of the display unit. Outputs are labeled a, b, c, d, e, f, and g, each letter corresponding to a standardized segment designation for 7-segment displays. The BCD inputs are designated A, B, C, and D in order from least-significant to most-significant. 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. 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 typical driver IC. 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.

How to identify and use both “active-low” and “active-high” logic inputs.

How to use 7-segment LED assemblies to create decimal digit displays.

How to use the 4511 7-segment decoder/display driver IC.

Lessons In Electric Circuits, Volume 4, chapter 9: “ Combinational Logic Functions”

Eight-position DIP switch (Radio Shack catalog # 275-1301)Ĭaution! The 4511 IC is CMOS, and therefore sensitive to static electricity!.

Common-cathode 7-segment LED display (Radio Shack catalog # 276-075).

4511 BCD-to-7seg latch/decoder/driver (Radio Shack catalog # 900-4437).

7 segment led display