Use the Latch and Unlatch Instructions to create and test PLC Logic that turns on the Green TP Light when the Start PB is pressed. The light should turn off when the Stop PB is pressed.

1 answer

To create and test a PLC logic that turns on the green TP light when the Start PB is pressed and turns off when the stop PB is pressed, follow the steps below:

1. Create a new PLC project using your preferred programming software (for example, RSLogix 5000 or TIA Portal).

2. Create two input tags/addresses and name them Start_PB (for the Start push button) and Stop_PB (for the Stop push button). Configure their types as BOOL (boolean) and their addresses according to your PLC's input module.

3. Create an output tag/address and name it Green_TP_Light. Configure its type as BOOL (boolean) and its address according to your PLC's output module.

4. In the main routine (or any routine that you prefer), create a Latch/Unlatch logic using the Latch (L) and unlatch (U) instructions.

5. Add a rung with an XIC (Examine If Closed) contact for Start_PB followed by an OTL (Output Latch) instruction for Green_TP_Light. This rung will latch the Green_TP_Light output when the Start_PB input is true.

```
|--[Start_PB]--(OTL)-|
| Green_TP_Light
```

6. Add another rung with an XIC (Examine If Closed) contact for Stop_PB followed by an OTU (Output Unlatch) instruction for Green_TP_Light. This rung will unlatch the Green_TP_Light output when the Stop_PB input is true.

```
|--[Stop_PB]--(OTU)-|
| Green_TP_Light
```

7. Save your program and download it into the PLC.

8. Connect the Start push button to the Start_PB input and the Stop push button to the Stop_PB input. Connect the Green TP Light to the Green_TP_Light output.

9. Test the logic by powering on the PLC and pressing the Start push button. The Green TP Light should turn on. Now press the Stop push button, and the Green TP Light should turn off.

This PLC logic uses latch and unlatch instructions to control the Green TP Light based on the status of Start and Stop push buttons. The light will turn on when Start_PB is pressed and will turn off when Stop_PB is pressed.