I have been doing teardown of mostly consumer electronics product since more than a year now and have done around 30 teardowns so far, you can check them here.
But, I always wanted to do teardown of wearables like Smart watch, fit bit, so here is a teardown of Boat Ultima Chronos Smart Watch.
BoAt Ultima Chronos Smart Watch comes with 1.96″ AMOLED Display, Advanced BT Calling, Option for DIY Watch Face Studio, Female Wellness, HR & SPO2 Monitoring, Energy & Sleep Score, it is IP67 and came with a Brown Leather strap.
I bought it from Amazon for 2,499 INR and I am 100% sure it did not cost more than 1000-1200 INR in manufacturing as they manufacture lakhs of units and a lot of cost goes further in selling, marketing, distribution.
In this blog, I will show you all parts inside a smart watch and try to explain all the details whatever I could understand. I really hope this will help you understand about internals of a smart watch.
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Smart Watch Packaging
When you receive the Smart watch it will come with a nice packaging.
Opening the smart watch is not that straight forward, you need to heat the watch from the outer side with a hot air gun that enclosure expands a little and then with a screw driver or a special plastic tool, you can remove the display. Remove the straps and switch off the watch before you start heating, also note that the watch will become quite hot so you need something to hold it
I didn’t had the right tool so I broke the display and the watch is not more usable. Don’t blame if you break your while opening 🙂
Smart Watch Display Panel
Once you open the smart watch, there will be two parts, one will be the display panel with attached capacitive touch and the other will be the main PCB board where all the circuit is there.
In the image below, you can see on the left side the display with touch panel is there and on the right hand side the main PCB.
On the display Panel you can see two FFC cables, one is getting attached to the Display Panel and the other one is hanging in the air, which will basically connect to the main PCB(MCU will drive the display)
You can see in the image below, the touch panel cable is connecting to the flexible PCB of the display.
Touch Panel controller used is CST820.
On the display Panel Flex PCB, you will see Power Supply circuit, that is basically Power Supply Circuit for the Display, it generates multiple power supplies for the display, it is part of the display itself. You will a display along with that, it is not designed by the smart watch manufacturer.
You can clearly see in the image below the DC DC Converter used has a marking 6802. Difficult to find the datasheet from the marking but you get the idea. If at all you need to find out you need to speak to the manufacturer of the display and they might give you this information.
There are also various capacitor used which will be required for the display to function(bias voltages). Once you get details of the display controller, you can see in the datasheet how typical circuit looks like. But as an application designed, you might not need to get into that level detail.
Smart watch Main PCB Panel
Let us now move to the Main PCB and see what all is there on that:
This connector (in the image below) is used for the Display Connection, in the connector oll display signals, power and touch signals, come together.
The main and interest part is Main Wearable SoC, Relatek RTL8763E is used for the smart watch.
External XT25F128F which is 128Mbit 16MB SPI NOR Flash, this will contain all the firmware of Smart watch, as per my understand they will be using a some flavor of RTOS as Wearable OS.
The smart watch has the Bluetooth connectivity and you can see the Bluetooth antenna using simple wire. See the image below.
I2C Accelerometer is this, on the left side of the RTL8763E SoC. I could not find the datasheet as KK7F marking on the device is not giving enough information.
There are other peripheral on board like MIC, Vibration motor, Speaker, Switch, Sensor, let me know connection for those devices.
Below is the Speaker amplifier and the red and black wires are going to the speaker, I will show you later when I open the PCB and show what is below that.
See below image, the holes on the side of the enclosure for the speaker sound to come out
Here is the condenser MIC and its two wire connection on the PCB. Direct wire connection saves on connector cost and height constraints in many situations, where you have cheaper workforce available this could be an option.
A close up image
On the side of the body, you will see the hole for microphone
There is a vibration motor to alert the user and here is connection for that, you can see a transistor/Mosfet is used to drive that.
Single button is given on the smart watch, you can see in the image below, it is not connecting to this PCB, it connects to the other flexible PCB where sensor, LEDs are located. I will show you that.
To see other parts below this PCB, we need to remove this PCB by opening the screws.
Once you open the PCB, you will see back side of the PCB with serial number and other marking, along with that you will see pads for spring loaded charging pins to connect.
Battery used for the smart watch is 3.8V DC at 280mAh only. You can see the BIS logo.
Now, if we remove the PCB, Battery to see further what are rest of the things which are on the back side of the enclosure:
You can see below is the vibration motor with glue so that it doesn’t come out of the enclosure while in operation.
This is the Speaker, wire connector the Main PCB.
Below are the magnets to attach the charging cable
Spring loaded charging pins
Microphone as shown above also
And this is the side switch
This is the Sensor Flexible PCB, for HR, SPO2 sensor
Photo Sensor and LED Interface front end used is HX3600 which connects to the main MCU via I2C interface.
You can clearly see in the image below that the Side switch of the smart watch is connected to flex PCB of the sensor, which finally connects to the main PCB on FPC connector
Sensor cable connects the main PCB on this connector
It is quite difficult to find out the part numbers of the Display, Speaker, vibration Motor, Sensor Photo Sensor and LEDs but I think you go the idea with above images and details. We need to spend a lot of time figuring it out.
I hope you found this smart watch teardown useful and learned something interesting 🙂
If you like it, do share it with others.
I am currently working as an embedded systems design consultant and helping companies build custom embedded products, develop test automation solution for their PCB.
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