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Comment by mastax | Hacker News Reader

Some Philips sonicare toothbrushes use(d) a 4-bit microcontroller from an obscure Swiss company. (From memory, since I can't find the EEVBlog video teardown) 52 bytes of RAM, custom size mask ROM, ? Kilohertz clock speed. It makes sense, they just needed a timer for the "2 minutes of brushing is up" feature, and maybe some battery management. It still surprised me that it was worth the hassle to save a few cents, even if they sell millions of the things. They must make insane margins: $80 for a vibration motor and $25 brush refills.

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It's pretty easy to make the hassle worthwhile, if you are selling (particularly many) millions of things. Even saving a dime on BOM for a million units shipped will pay an engineer year, roughly.

I still remember a friend relating with a mixture of horror and fondness that in 15 years probably the biggest impact he ever had to the bottom line of [big computer manufacturer no longer in existence] was re-routing a PCB in a way that let them make it smaller with no functional change. The materials cost savings over product lifetime was in the 7-8 figures range, he claimed.

A product I was working on had different variants based on what parts are populated. There were config resistors to help route the signals based on what was populated. I replaced that all with a simple software lookup table in firmware to reroute the signals correctly. Furthermore I figured out how to auto-detect the dozens of supported configurations on first bootup. The PCBs were very small so I made the board designers job a lot easier due to eliminated resistors. The factory folks were thrilled that they didn't have to manage the jumpers.

I would hire you. These techniques should be applied pervasively.

Could you write a guide? I would buy it.

Thanks for the kind praises. Unfortunately I'm not much of a writer though I have lots of interesting experiences that I tell my friends and coworkers.

A big part of how I'm today is due to my boss at that time. One of the most brilliant engineers I worked it. He also gave us a lot of time and freedom to think of these kind of approaches. Sadly these days a lot of companies are always in a rush so one can't think things through properly.

I did a teardown of a Sonicare toothbrush that used an 8-bit PIC 16F1516 microcontroller. There's a lot more going on in the toothbrush than I expected. I expected a simple motor, but there's a mechanically-complex resonant coil mechanism, driven by an H-bridge. There's some expensive manufacturing in there. Another interesting thing was the toothbrush has a "pressure sensor" to tell if you're brushing too hard, but it's really a Hall-effect sensor.

http://www.righto.com/2016/09/sonicare-toothbrush-teardown.h...

Maybe one of these?

https://www.emmicroelectronic.com/catalog?title=&term_node_t...

EM Microelectronics is actually not so obscure. They belong to the Swatch group and are specialized in ultra lower power analog and mixed signal circuit. Obviously, first for watches.

Are you thinking of this Braun teardown? https://www.youtube.com/watch?v=JJgKfTW53uo That indeed uses a 4-bit micro from a Swiss company (The only sonicare teardown I found was a forum post)

Yep, that must be it. Thanks!

Mentioned EEVBlog teardown: https://www.youtube.com/watch?v=JJgKfTW53uo

I don’t know how, or why, but I’ve bought the same Phillips toothbrush for $20 from AliExpress when my original broke.

And I buy the heads from Asia too for a fraction of the store price.

The heads aren’t Phillips, just clones right? I would expect the brush you are buying to be a clone also, or at best a good knock off. Phillips is pretty disciplined about their pricing internationally.

I buy cloned heads (but not the main brushes) and find them completely adequate.

The base was legit (or a 3rd shift kinda thing?), but the heads are definitely generics.

Agreed, they work fine.

I’m very doubtful they were legit, anything labeled third shifts are almost always fakes. I can’t find any soniccare on alibaba (just a lot of clones), they have stuff on TMall, but all the prices are normal.

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