Sonicare toothbrush teardown: microcontroller, H bridge, and inductive charging


Ken Shirriff did a teardown of a Sonicare electric toothbrush:

The photos below show the top and bottom of the toothbrush internals. I expected to find a simple, low-cost mechanism, so I was surprised at how much complexity there was inside. The vibration mechanism (right) is built from multiple metal and plastic parts screwed together, requiring more expensive assembly than I expected. The circuit board is literally gold-plated and has a lot of components, even if it doesn’t quite reach Apple’s level of complexity. Overall, the toothbrush’s internal design is high quality (except, of course, for the fact that it quit working, as did an earlier one).

More details at Ken Shirriff’s blog.

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  1. Got two of them. If you let the battery run flat, they don’t charge!
    You have to pull the battery, and get enough charge in so the controller runs, THEN, they will recharge in the normal way.
    Very odd.

  2. I have a suspicion they have some form of suicide device them – once activated the micro doesn’t go into proper sleep (or similar), so the battery ends up only lasting a couple of days. I’ve had many of the years and their final demise always seems very similar. The most notable one was a unit that was only 11 months old – I dropped it on the floor and it broke part of the mechanical linkage inside. I opened the unit up, repaired my damage and reassembled it. Mechanically it was fine, however it went from the battery lasting many weeks to lasting only 48 hours overnight.

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