Microbot Push Teardown

ID: 72598

Description: A few months ago, we pre-ordered the MicroBot...

Steps:

  1. Removing the 4 Torx screws and 1 regular one beneath the black rubber pad shows us a gearbox, 2 PCBs and a battery
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  2. According to its specs, the MicroBot has a battery life of about one year. The battery is rechargeable, using a regular 5V charger with a micro USB connector.
  3. Battery charging circuit
  4. Charging IC
  5. Transistor to control the red and green LEDS next to the USB port, indicating whether or not the battery is fully charged
  6. Battery protection circuit
  7. These types of ICs are used to “sense” the current
  8. When the specified current limit has been reached they trigger a switch that will break the current path to the battery. The switch that is triggered in this case is a Dual N-Channel Enhancement Mode Power MOSFET, in this case the 8205A
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  9. The capacitive touch button and matching circuitry (marked in red)
  10. The big gold circle you see in the middle of the PCB is a capacitive touch button. It’s simply an exposed piece of copper
  11. The TTP223B chip, this chip is a one-key touch pad detector that can detect the touch of a human finger on the touch pad. It does this by using the “Frequency Change” method
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  12. The bluetooth chip and antenna (I had to remove a metal shield to reveal the chip;)
  13. The bluetooth chip, in this case the nRF51822 Nordic Semiconductors (It’s a 2.4GHz ultra low-power bluetooth chip built around a 32-bit ARM® Cortex™ M0 CPU)
  14. To the right of the nRF51822, you can see two oscillators, one 16MHz and one 32.768kHz (marked in orange), which generate the clock waveforms for the CPU
  15. On the bottom (marked in yellow) you see the antenna circuitry and the PCB antenna itself. As you can see, they did not use a balun chip, but instead created a matching network using some capacitors and inductors.
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  16. This circuit is located on the back of the PCB
  17. I could not trace back the datasheets of the actual components used, but after probing the upper IC with an oscilloscope I noticed that this is also a voltage regulator. This one boosts the voltage from 2.5 volts back to 4 volts to power the motor and the motor controller
  18. Motor driver
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  19. Opening up the gearbox was fairly simple: I just had to remove two screws to expose the gears and the motor
  20. If we count all teeth of the gears we come up with a speed reduction of 948.41
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