43 SKILL 10 DESIGN A PLC PROGRAM THAT USES AN ANALOG OUTPUT TO CONTROL AN SCR POWER CONTROLLER Procedure Overview In this procedure, you will design a PLC program that controls an SCR Power Controller with an analog output signal. In this application, the BCD/LED Station will provide a BCD value that is used by the PLC program to output an analog signal. Do This 1. Design a PLC program given the following information: Scenario: You work for a company that manufactures industrial electrical ovens. The ovens have an SCR power controller that regulates the amount of electric power to the electrical heaters of the ovens. The customer wants to use BCD thumbwheels to control the analog output signal to the SCR power controller. The input signal to the SCR power controllers will range from 0 to 5 milliamps. The BCD values will range from 0 to 7999. BCD THUMBWHEELS DISCRETE INPUT MODULE ANALOG COMBINATION MODULE 0500 PLC REMIIN O ALLEN BRADLEY SCR POWER CONTROLLER TO OVEN OUTPUT SIGNAL 0 TO 5 mA OUTPUT CHANNEL 0 AND WORD ADDRESS O:6.0 -TEMPERATURE RANGE - 0 TO 7999°C OVEN Write the PLC program to use the BCD thumbwheels to control the signal from the analog output module. The general sequence, I/O diagram and pictorial are provided. General Sequence · The BCD value is converted into an integer value. · The integer value is used to control the output of an analog module. · The milliamp output (0 to 5 milliamps) of the analog module controls the power output of the SCR power controller (simulated on the analog display). · Turn the SCR power controller fully on with any output exceeding 5 mA. 1:1/0 1:1/1 1:1/2 ANALOG CHANNEL 1:1/3 0 OUTPUT O:6.0 I:1/4 1:1/5 1:1/6 4:1/7 1:1/8 1:1/9 I:1/10 1:1/11 I:1/12 1:1/13 I:1/14 I:1/15 Figure 64. PLC I/O Diagram 2. Make sure that all power to the PLC trainer and its components are off. 3. Mount the 89-BCD/LED Station to the left-hand side of the PLC trainer's Field Device Unit. 4. Mount the 89-AS-B Analog Station to the right-hand side of the PLC trainer's Field Device Unit. 5. Verify that the 1746-NIO4I analog module's dip switches are set for voltage input signal. If not, make it so. 40630-AB LAP 14 ANALOG OUTPUT MODULES Copyright @ 2012 Amatrol, Inc. 77