From the course: Learning PLC Ladder Logic: 2 Diving Deeper

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LED displays in PLC

LED displays in PLC - Ladder Logic Tutorial

From the course: Learning PLC Ladder Logic: 2 Diving Deeper

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LED displays in PLC

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- [Instructor] One of the devices that are used with PLC as an output is LED display. LED displays are example of PLC devices that use BCD numbering system. They display values from zero to nine and in order to show a certain number, very similar to a thumb wheel concept, LED display show the values that are based on the BCD values received using a binary weighing. So to show a number eight, then the values to be sent to the LED display are one, zero, zero, zero. This is how it works. The binary number that needed to be shown on the LED display gets converted to a BCD value then sent out to the display that shows the number in decimal. And to do so, PLC software uses an instruction called TOD. TOD behaves similarly to FRD that it converts the BCD value to a decimal number. So when the numbering needs to be shown as two digits, it looks to each four bits separately.

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