During a conversation with a client, they mentioned that their single-button start/stop program was too cumbersome and asked if there was a simpler way. I had encountered similar problems in previous projects and had only written a quick code without much thought. Adhering to the principle that simpler program design is better, I considered several solutions to find the most concise approach. A colleague commented that in practical applications, choosing a self-locking button, rotary switch, or key switch would result in the simplest and most straightforward program. To encourage divergent thinking and provide beginners with more instruction exposure, we offer several methods for implementing start/stop with a single button. 1. Recommended Method 1: SR Instruction Setting the Master Bistable Trigger (SR) is a latch that sets the master bit. If both the set (S1) and reset (R) signals are true, the output (OUT) is true. SR Instruction Truth Table: Implementation method: 2. Recommended Method Two: RS Instruction Reset Master Bistable Flip-Flop (RS) is a latch that resets the master bit. If both the set (S) and reset (R) signals are true, the output (OUT) is false. RS Instruction Truth Table: Implementation method: 3. XOR: If the values ​​a and b are not the same, the XOR result is 1. If the values ​​a and b are the same, the XOR result is 0. Implementation: 4. Implementation method of set/reset instruction: 5. Implementation method of counter instruction: 6. Integer addition instruction, similar to a counter. Implementation method: 7. Implementation method of invert instruction: 8. Implementation methods for circular left or right shift instructions: In conclusion, when designing a PLC control scheme, we should consider how to reduce the number of input points required by the PLC. To reduce the number of input points, there are actually several methods depending on the situation. One such method is to use a single-button start/stop control. There are many ways to implement single-button start/stop control using a PLC; this is just one example. If you are interested, you can write one that suits your own thinking. Scan the QR code → Click to follow