【Training Camp】Smart Socket-896922A

1. Analysis of failure reasons:

1) I designed the metering circuit according to the technical manual of Shanghai Belling BL0937 chip, but failed to design the circuit according to the schematic diagram of Tuya Smart's recommended solution. As a result, this solution only realized the switch control function and failed to fully realize the power statistics function. 2) This electricity statistics chip requires the high voltage and low voltage to share the same ground. Since the self-sufficient power module is used, it causes isolation, resulting in no common ground, so the metering chip cannot work properly. Later, I modified the flying wire by myself and connected the live wire to low-voltage GND. Although the value can be displayed, the leakage of the metering chip caused a hidden safety hazard. The flying wire cannot be used with the same ground, and a dedicated power circuit must be designed.

**Follow-up improvement plan: **As a practical attempt, I gained a lot of experience. In the next design, the power circuit and metering circuit will be designed according to the plan provided by Tuya; the 220V circuit will be optimized to isolate strong and weak electricity; and an insulating shell will be designed.

2. Experience gained from this design:

1.) This metering circuit requires high and low voltage common ground wires and cannot be isolated. Operations must be cautious and safety first! Safety first! Safety first! 2.) The circuit design must strictly follow the schematic diagram provided by the manufacturer. Understand the principles and then design. The circuit must be designed strictly in accordance with the principles. 3.) Familiar with the process of Tuya Smart Free Development and Circuit Design. 4.) Due to time constraints, I was unable to design the casing. The appearance should be considered in advance as a redesign the next time. 5.) Although program-free development is simple and convenient, it is very inconvenient to find the cause without a program after a problem occurs. Free development is only suitable for existing mature design solutions. In the end, the power statistics function failed to be debugged. 6.) There are regrets in this product, but in the future, we should consider more principles and practical applications when designing, and slowly work hard to make a mature design. I also gained a lot of experience from this failure and can avoid many detours in the future, which is also a good thing.

I gained a lot from this training camp. Thanks to Tuya Smart and Lichuang for their guidance and help!