Rab18’s Weblog

Initially the aim is to just get some numbers displayed on the four digit seven segment display. Using the circuit diagram from circuit wizard I was able to setup this protocircuit (See link for more info on protoboard). I also used the data-sheet for the four digit seven seg display. This enabled me to identify what each of the 12 pins on the display do. Using this data-sheet and the information I already had I was able to calculate what resistors were required between the seven pins from the 4511 and the seven pins on the display.

Calculations for Resistors.

IF=20ma    Max  Voltage 2.5  V/I = R   2.0/0.02= 1oo ohms resistor.

There is a 10% forgivness with this sum, so I selected 120ma resistors between the seven outputs of the 4511 and the seven pins of the display, the other five pins are connected to ground. These pins power the four digits and the dots between the numbers.

The 4511 is designed to be used with a common cathode display. The aim of this circuit is to count 0 to 9 on each of the four digits of the display.  The diagram from circuit wizard demonstrates the possibility of using four switches as a means to input the 4511. An open switch represents 1 and a closed switch represents 0. Using circuit wizard as a means to experiment it allowed me to formulate a truth table. This can be used to identify the inputs needed for 4511 to display each number.