Objectives: Upon completion of this laboratory, you will be familiar with FRD (convert from BCD) and TOD (convert to BCD) instructions and comparison instruction (Greater than or equal) and its use within the ladder logic to control a process.
BCD I/O LogixPro HMI*
*Simulator courtesy of The Learning Pit LogixPro 500
Process Description: Study and experiment with the LogixPro BCD I/O simulator shown in The Figure above. Design a PLC program to perform the conversion from a positive degree Fahrenheit (F) to the equivalent degree Centigrade (C). The degree F is limited to two BCD digits (00 to 99) in order to match the simulator thumbwheel switch setting. The formula for the conversion is given by the following equation:
C = (F – 32) * 5 / 9
1. Design the specification for the temperature HMI and specify the input/output range allowed by the given simulator.
2. Write the ladder logic program to capture the BCD degree F entered form input I: 0 and display the output O: 2 in degrees centigrade using the BCD format.
3. Flash output O: 2 for negative degree C and maintain it for positive values?
4. Modify the program design to allow for input in hexadecimal, which accommodates degree F from 0 to 255. Display the degree C in BCD format.