PLC is a small industrial computer. If there is a problem with the PLC, the first thing to rule out is whether it is the PLC itself or the peripheral equipment. If there is a problem with the PLC itself, the error light will usually turn on or the red light will flash. Under normal circumstances, the green light for operation is on. If there is a problem with the PLC itself, the probability of successful repair is not high.

Some PLCs store data through internal batteries. When the battery voltage is below a certain threshold, the battery warning light will turn on. At this point, it is necessary to replace the battery and charge it. If the battery is completely discharged or there is no charging operation when replacing it, RAM data is usually lost. At this point, you need to refresh the program and data. Therefore, we should develop the habit of program and data backup, otherwise we will have to reprogram and debug at critical moments.

Power outages also account for a certain proportion of vehicle malfunctions. The input of PLC is usually 220AC, and some things require 24V or 12vl input, but there is a chip inside that requires 5VDC or 3.3vdc. Therefore, there is a switching power supply voltage reduction circuit. Due to high current and high temperature, circuits are prone to problems under certain harsh high temperature or dust conditions. If the PLC indicator light is not on, the switch power supply is usually disconnected. The switch power supply is damaged. For people with a certain level of electronic maintenance, this is not particularly difficult. For example, there is a high possibility of damage to the control chip 384x or switch tube. Generally speaking, only replacement is needed

If the red light suddenly flashes or the error light comes on, the motherboard is usually damaged or the program is lost. You can try reintroducing this program. Otherwise, the maintenance value is not significant. You can only replace the watchdog IC and reset circuit of the chip, or replace the crystal oscillator of the chip at most. If you still can't solve this problem, I suggest you give up. The integration level of this device is too high and difficult to maintain. Moreover, the price of the motherboard is not particularly expensive and its value is not significant.