Failure Analysis of Air Conditioner Button Circuit

Failure Analysis of Air Conditioner Button Circuit

Where is the button circuit in the inverter air conditioner? The first is the function keys on the display panel, and the second is the automatic switch on the main board. The main purpose is to transmit user instructions and achieve the purpose of information interaction. So, how does it work? What are the common after-sales failures? This article is through the analysis of the circuit, hoping to give you some help in the after-sales maintenance.

　　 1. Circuit principle

When the button is off, the circuit has no loop, and the microcontroller is in a high level state; when the button is pressed on, the 5v DC power is connected to the power ground through R1, forming a loop, and the PIN port is in a low level state. . In this way, the microcomputer can receive the user's button information. Some use membrane buttons. The upper and lower membranes are coated with conductive rubber circuits, and there is a membrane in the middle with holes to isolate the two membranes with conductive rubber. The button is in the position of the hole. When the button is pressed, two films with conductive rubber pass through the round hole in the middle, connect the circuit, and output through the chip code.

　　 2. Common faults

Case number one

　　 Fault phenomenon: A wall-mounted air conditioner automatically restarts after being used for a period of time.

　　 Reason analysis: There are three situations for automatic reset, the first is that the first is too low; the second is electromagnetic interference; the third reset button circuit is faulty.

　　Troubleshooting: Check the power supply, no abnormalities are found; check the surroundings and find no sources of electromagnetic interference. After checking the automatic switch, it was found that it was in the joint state, and the switch was mainly connected to the reset circuit of the single-chip microcomputer. After further analysis, it was found that the switch had silver ion migration.

　　 Case 2

　　Fault phenomenon: A 2-hp cabinet machine has a button failure fault.

　　Cause analysis: General inspection found that the button failed but the display was normal, so the power supply should be normal. Further inspection found that the button was corroded and broken.

　　Troubleshooting: Replace the button

　　 Three, additional knowledge points

　　 1. In order to avoid accelerating electromigration, the manufacturer will set the effective time of the automatic button as 5 minutes after power-on, after which the button will become invalid.

　　2. After-sales maintenance can determine which type of problem is based on the phenomenon. For example, the reset phenomenon is an automatic button. When the function is abnormal, the display panel button is displayed.

　　 3. Some buttons are dirty, which can be cleaned with alcohol, or foreign objects can also be cleaned.