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

Unlock the full course today

Join today to access over 24,600 courses taught by industry experts.

Thumbwheel in PLC

Thumbwheel in PLC - Ladder Logic Tutorial

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

Start my 1-month free trial Buy for my team

Thumbwheel in PLC

“

- [Instructor] A thumbwheel switch is one example of an input device that uses BCD system. Thumbwheel has four output connections and a common output. Each of the four connections, the first, second, fourth, and eight, represent the binary weighing of that number. And they are individually wired to the PLC input. So for number seven, the PLC sees it as a BCD 0111, representing the decimal number. The thumbwheel, or any other input devices, are connected to the input model of the PLC. Then, within PLC, there is a BCD to binary conversion for that input. Now if we want to enter a two-digits number, then thumbwheel switches can be grouped together to support multiple digits. Now this brings us to an issue that need to be addressed. When using two thumbwheel switches, the software wrongly sees the digits as one long number. So instead of showing a binary number, a presentation of 87, the PLC wrongly interprets that as one…

Contents