I did a teardown of Tata Power Smart Switch. Wanted to see if Smart Switch from Tata is using same OEM design or if they did something different.
When I opened the enclosure, I found the architecture is similar but choice of components are different and they used an MCU + ESP8266, that’s was quite strange.
Other than Wi-Fi capable 3 10A switch(relay) it has single phase energy metering also.
Packaging and Enclosure was good as I saw in Sonoff smart switches.
Here is a close up of the PCB.
Power supply section take the AC mains input and with the help of AC to DC converter IC generates 12V DC.
It has used SM7075-12 PWM non-isolated power converter IC for converting 85V-265V AC to 12V DC.
12V is further converter to 3.3V DC using post DC DC Converter circuit using S47Bbx3 dc dc converter IC. Could not find a datasheet.
Main controller used is ESP8266 with 1MB/8Mbit SPI NOR Flash(P28Q80) for the Wi-Fi and also a Novutron MCU N76E003AT20, it’s a 8051 core MCU with 18KB Flash and 1KB RAM.
You can see a copper wire is used a Wi-Fi antenna.
I was wondering why did they use this Optocoupler, probably for detecting the AC input. so that when power goes off, it can quickly save the reading in the Flash while power is still there on the board.
3x AC Relays are used for load control. Manufacturer is SINETONG and part number is 973-12VDC-SL-A.
Typical AC voltage rating of 250V AC and Max it can handle is 277V AC. Its rated for 10A. You can see it is UL Rated.
It used a single phase Hiliwie Tech HLW8012 IC for AC Energy measurement. So basically, it is not measuring energy for each load but for combined load.
Typical circuit is as shown in the image below
That’s all on the board other than 5 terminal input. 2 for AC(P, N) and 3 for Load, L1, L2, L2. N is common for load and Power input.
I hope you found this teardown useful and learned something new today!
If you have any questions please ask in the comments section below, I will try to respond as soon as possible.
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I am currently working as an embedded systems design consultant and helping companies build custom embedded products, develop test automation solution for their PCB or complete product.
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