This article is written by Mark Hughes from Allaboutcircuits.com website.
In this teardown, we dismantle a BB-8 droid (or, at least, an RC toy version) to see what’s inside.
BB-8 is a novel app-enabled robot that is encapsulated inside a sphere. The center-of-mass of the robot is offset from the center-of-rotation, and movement of the center-of-mass creates a torque on the shell that causes movement.
The BB-8 toy. Image courtesy of Sphero.
The geared differential drive mechanism inside the sphere allows for rotational and translational movement of the robot, while a deeply offset center-of-mass ensures the internal mechanisms remain properly oriented through most movements. The toy can be controlled through proprietary apps on iOS and Android, as well as through optional accessories.
This is an entirely enclosed toy, and the batteries must be charged wirelessly through a pair of coils whose geometry conforms to the shell.
Cutaway image of the Sphero toy from manufacturer
To see me rip open this beloved droid, check out my disassembly video below:
The base of the BB-8 toy houses a circuit board and spherically-wrapped helical coil that charges the device wirelessly. The overall goal of the circuit is to create a rapidly changing electromagnetic field around the coil that delivers energy to a second coil inside the toy.
Both sides of the PCB charging circuit inside the BB-8 base. The three two-pin shrouded connectors connect to an LED, a momentary switch, and the USB charger.
This IC has no top-side markings, making positive identification impossible. Based on its connections to the crystal, LED, and button, it’s a safe bet that this IC is an inexpensive microcontroller responsible for the overall logic and state of the charge circuitry.
This SOT23-5 packed IC has a top-side marking of “QW5PC”. It’s location near the USB power input and connection to other components lead me to believe it is a voltage regulator.
This IC is marked “X2” and its output leads through a diode to a large transistor. There is a good chance that this IC, when enabled by U1, establishes the oscillation frequency for the charging coil.
This small IC is labeled “D22” and its purpose is unclear. It does appear to connect back to U1, although without probing, it’s impossible to deduce its function from the connected passives alone.
This transistor marked “4606 GA5U16” feeds two large metallized polypropylene film 333J capacitors that are in turn connected to the charging coil.
Spherically wound helical coil, illustrated in Orange in the image below. This coil sits atop a highly-permeable gray tape on the circuit-board immediately below the coil. Charging occurs when the toy is set inside the charging base and energy is transferred from the outer coil in the base (orange) to the inner coil in the toy (green). More permeable tape sits atop the coil that lies inside the toy.
The top and reverse side of the main circuit board are shown above. Numbering follows reference designations on circuit board.
STM32F3 series microcontroller: This 32-bit Arm Cortex-M4 seems overpowered for the task at hand: Interface with a BLE chip, a motor-controller IC, a sensor IC or two, and control two RGB LEDs. Similar disassembled toys from other manufacturers have used less-expensive 32-bit Cortex-M0 cores, and I imagine some cost-cutting companies could envision this design on an 8-bit microcontroller, albeit at reduced performance rates.
CSR 1010 A05U 611AX: A Bluetooth Low Energy radio with integrated microprocessor. Based on the presence of the more powerful STM32F3 microcontroller, I doubt very much that the engineers used the integrated microprocessor to its fullest extent. I imagine that this chip is simply used as a network processor.
24512RP K5288: A 512 kBit serial I2C EEProm. These ubiquitous serial rams are made by all the major memory manufacturers and store plenty of data for firmware upgrades.
Huatai HT6292 1531: A Li-ion charger IC that controls the charge state of the two onboard Li-ion batteries (3.7 V 340 mAh)
UTC SETM LM358G 59: A dual operational amplifier. The 358 has been around for decades as a general purpose operational amplifier. Without probing or more information, I cannot deduce the purpose of this IC.
No visible topside markings.
The Sot23-5 packaged IC labeled “JA33 1GB5V” is likely a linear voltage regulator used to deliver power to the board from the attached batteries.
Marking: A34 A1325 438
6552G 534 a8 is a dual h-bridge brushed motor driver IC that controls the geared wheels that drive the toy. Since brushed DC motors are open-loop devices, two Hall-effect sensor ICs are located on the body of the motor to sense spindle position and provide feedback to the main microprocessor.
This is an incredibly well made device that speaks well of the engineering acumen of the design team. If you can help identify any of the ICs above, please leave a comment in the original article!