1. We use the X0 input as the timing start signal. When the timing signal is received inside the PLC, the bit soft element X 1 is turned on, and "ldx0" is directly input into the ladder diagram on the left bus.

2. We use T0 as the internal timer of PLC. At this time, we should pay attention to the types of timers: t0 ~ T 199 means 100ms general timer, and T200 ~ T245 1 means 0ms general timer. You can input "outt0k30" at the back end of the input signal, and k30 means 3000ms, that is, 3 seconds. 3. When the timer ends, there needs to be an output signal, which can control external equipment or be used as a warning light. We use Y0 as the output. 4. If the timer is not reset after the end, the timer will keep the last value, and we can increase the reset command to reset C0. When finished, you can click the test button to simulate. 5. In the logic test dialog box, you can add a bit component monitoring screen. Click "Soft Component" in the menu, then select "Soft Component Window" and select X and Y. At this time, you can operate and monitor the input and output of the programming program. 6. In the X input dialog box, click the input button once to lock the input, and click it twice to release the input. Click X0 and wait for 3 seconds, and Y0 will be output. At this point, if you click X 1 twice, you can reset the timer and then reset it.