A brief discussion on the failures and phenomena of PLC maintenance

PLC maintenance:

Power off and test continuity!!

Note: Use the buzzer mode of the multimeter to test the continuity. Connect the red and black wires of the multimeter in advance.

The first step is to turn on the power (pull up all the gates). Note that one of the two gates on the right hand side must be turned on!!

Phenomenon: Fault point 7 is not broken, and the PLC light is on (run); if fault point 7 is broken, the entire PLC light is off. Use a multimeter to test the continuity, one probe to test U01 from the power supply, and one probe to test U02 on the PLC.

The second step is to check whether 0V and 24V are powered, that is, fault points 13 and 14.

Phenomenon: If there is no problem with fault points 13 and 14, the run light on the PLC is on, and the lights of I1.0, I1.1, and I1.2 on the PLC are on. If No. 13 is broken or No. 14 is broken or both No. 13 and 14 are broken, the run light on the PLC is on (because there is no problem with fault point 7), and the three lights of I1.0, I1.1, and I1.2 are not on.

(1) No. 13 disconnection: Find the line that 0V comes out (on the upper right of the PLC) and the line that 0V comes out on the button side to test the continuity.

(2) Breaker No. 14: Find the 24V line (at the upper right corner of the PLC) and the 1M line on the PLC (at the first port of port I) to test for continuity.

Pay special attention to the brightness of I1.0 (FR1), I1.1 (FR2), and I1.2 (emergency stop) on the PLC. If I1.1, the middle light, is dim (off), it means that the line of I1.1 is broken, that is, the fault point 12 is broken. Point one meter pen to PLC I1.1 (line 010) and the other meter pen to line 010 on FR2.

There are no problems with fault points 7, 12, 13, and 14. The lights representing the four fault points are all on.

Step 3: Press the start, limit and slot limit buttons in sequence, and the corresponding input port lights will light up, indicating that there is no problem with the input;

If one of them is pressed, the corresponding input port will not light up.

(1) Press the start button, and the I0.0 port light on the PLC does not light up, indicating that the fault point 8 is broken.

(2) Press the upper limit switch button, and the I0.2 port light on the PLC does not light up, indicating that the fault point 9 is broken.

(3) Press the limit switch button of the aqueduct slot, the I0.5 port light on the PLC does not light up, and the fault point No. 10 is broken

(4) Press the limit switch of the clean water tank, the corresponding I0.7 port on the PLC is not lit, and the fault point No. 11 is broken.

Because it is a button, pressing it turns on the power, and releasing it turns off the power. So you have to press it while watching whether it lights up.

Step 4. Check output Q, turn on the switch and follow the control flow chart (up and down means the hook is up and down, left and right means the car is moving, when the up indicator or down indicator jumps, the three indicators of the hook light up, when the right and left indicators jump, the driving indicator lights up, and one of the lights does not light up, indicating that there is a problem with the fault points 1 to 6)

There are no problems with the input. Press the left limit button and the lower limit button, then press the start button (pressing these three at the beginning is to ensure the position at the origin). You will see the rising indicator light up, and the three indicator lights of the hook also light up (the three indicator lights of the driving are off) → Press the upper limit switch, the right indicator light up, and the three indicator lights of the driving are also on (the three indicator lights of the hook are off). At this time, it is assumed that the vehicle is already at the right limit → Press the aqueduct limit switch, the hook descends, and the descending indicator light up (the three indicator lights of the hook are on) → Press the limit button, the aqueduct indicator light up, and then the rising indicator light jumps (the three indicator lights of the hook are on) → Press the upper limit button, the left indicator light (Three indicator lights for driving are on) → Press the recovery tank limit, the descending indicator light is on (three indicator lights for the hook are on) → Press the limit, the recovery tank indicator light is on, and then the rising indicator light jumps (three indicator lights for the hook are on) → Press the upper limit, the left indicator light is on (three indicator lights for driving are on) → Press the clean water tank limit, the descending indicator light is on (three indicator lights for the hook are on), → Press the limit, the clean water tank indicator light is on, and then the rising indicator light jumps (three indicator lights for the hook are on) → Press the upper limit, the left indicator light is on (three indicator lights for driving are on) → Press the left limit, the descending indicator light is on (three indicator lights for the hook are on) → Press the limit, return to the origin and then automatically jump to the rising indicator light, and cycle the next process.

Faults and symptoms:

(1) Fault point No. 15 is the coil KM1 that controls the rise. If it is broken, the rise indicator light will be on when the rise indicator light jumps during the entire control process, but there will be no suction sound (the coil is not suctioned), and the three indicator lights on the hook will not be on. KM2 is the coil that controls the descent. There is no fault point set on the drawing. When the descent indicator light jumps, the light will be on and a suction sound can be heard, and the three indicator lights on the hook will be on.

(2) Fault point No. 16, KM3 is the coil controlling the left lane. If it is broken, when the left lane indicator light jumps, the light comes on without a sound of engagement, and the three driving indicator lights also do not light up. KM4 is the coil controlling the right lane. There is no fault point set on the drawing. When the right lane indicator light jumps, the light comes on with a sound of engagement, and the three driving indicator lights also light up.

(3) Fault point No. 17 controls whether the descent indicator light is on. If there is a fault, the control process presses a certain slot limit, the hook should descend to a certain slot, and the descent indicator light is not on.

(4) Fault point 18: After starting, the up indicator light comes on. Then, press the upper limit and drive right. The right indicator light should come on, but it does not. This indicates that the fault point 18 is broken.

(5) Fault point No. 19 controls the indicator light of the recycling tank. Follow the control process and press the limit of the recycling tank. The descent indicator light comes on. Then press the limit, and the recycling tank indicator light comes on. Then the rise indicator light jumps. However, the rising indicator light jumps when the recycling tank indicator light does not. This indicates that there is a fault at No. 19.

(6) At fault point No. 20, when starting the control process, the rising indicator light is on first without any engagement sound. Then, the right indicator light is on without any engagement sound. After completing the control process, only the rising indicator light, the falling indicator light, the right indicator light, and the left indicator light are on, but there is no engagement sound. All other lights are off.

Fault points 1 to 6 control the six lights on the hook and the crane. When following the control process, when the three lights on the crane are on, one of the three lights is not on. After completing the entire control process, it is found that the light is not on, so the circuit where the light is located is tested for continuity.