As we saw in the previous tutorial, a Digital Decoder IC, is a device which converts one digital format into another and one of the most commonly used device for doing this is called the Binary Coded Decimal (BCD) to 7-Segment Display Decoder. 7-segment LED (Light Emitting Diode) or LCD (Liquid Crystal Display) type displays, provide a very convenient way of displaying information or digital data in the form of numbers, letters or even alpha-numerical characters.
Typically 7-segment displays consist of seven individual coloured LED's (called the segments), within one single display package. In order to produce the required numbers or HEX characters from 0 to 9and A to F respectively, on the display the correct combination of LED segments need to be illuminated and BCD to 7-segment Display Decoders such as the 74LS47 do just that.
A standard 7-segment LED display generally has 8 input connections, one for each LED segment and one that acts as a common terminal or connection for all the internal display segments. Some single displays have also have an additional input pin to display a decimal point in their lower right or left hand corner.
In electronics there are two important types of 7-segment LED digital display.
* 1. The Common Cathode Display (CCD) – In the common cathode display, all the cathode connections of the LED's are joined together to logic "0" or ground. The individual segments are illuminated by application of a "HIGH", logic "1" signal to the individual Anode terminals.
* 2. The Common Anode Display (CAD) – In the common anode display, all the anode connections of the LED's are joined together to logic "1" and the individual segments are illuminated by connecting the individual Cathode terminals to a "LOW", logic "0" signal.
Common Cathode and Common Anode Format
Electrical connection of the individual diodes for a common cathode display and a common anode display and by illuminating each... [continues]
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