How do I understand this interlock logic?
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Experts, how do I read this sequential logic diagram?
When the temperature is normal: when the temperature is below 1650°C, all 3 \"or\" operations (≥) produce a 1, and the \"and\" operation also produces a 1. The value 1, after waiting for the rising edge, becomes 0 via the \"not\" operation; it then outputs 0 after that delay. The value 0, after being processed by the \"not\" operation, becomes 1 and serves as the input signal for the S set terminal of the SR flip-flop. The flip-flop outputs 1, the solenoid valve is activated, the actuator is inflated, and the pneumatic valve closes. When any 2 temperatures (chosen from 3) are above 1650°C, the ‘AND’ operation yields 0,0; after a delay until the rising edge, the ‘NOT’ operation results in a value of 1. After another 20 minutes of delay, the output becomes 1,1. The ‘NOT’ operation then converts this value to 0, which serves as the input signal for the S-set terminal of the SR flip-flop. At the same time, 1 also acts as the input signal for the R-reset terminal of the flip-flop. The flip-flop outputs 0 at this point, the solenoid valve loses power, the pressure in the actuator is released, and the pneumatic valve opens.
For that 20min module in the legend, I need to check the instructions to determine whether it refers to toff, ton, or tp
For interlocking, a three-out-of-two logic is used; the rise edge at high temperature is delayed by 20 minutes. The intermediate logical relationships are examined step by step, and finally the flip-flop is set to output 0. When the temperature returns to normal, it is reset and the system resumes normal operation. The logical relationship is still quite clear.
Take the average of the three temperatures; if this persists for 20 minutes, an interlock is triggered.
It is necessary to check whether the function in the middle is a rising-edge delay or a pulse function – it seems to be a 20-minute pulse. In that case, the interlock action should be initiated after a three-out-of-two trigger condition is met, and it will end either after 20 minutes or when the reset button is pressed.