Strange failure mode of toothbrush

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#1
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My electric toothbrush used to have two speeds, press once for slow, twice for fast, a third time for off.

Now it goes from off to fast to off.

It's not likely to be switch bounce, as it's totally consistent. I assume it has a micro, as it does the little glitchy thing to tell you when to move to another area, and when to stop.

I'm not going to try and fix it or anything, but it seems a bit unlikely to me that some memory location had failed with this precise effect. If it was made by Apple, I'd say they'd reprogrammed it to encourage me to buy a replacement.

 

Four legs good, two legs bad, three legs stable.

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EEVblog once did  a bit of reverse engineering.

That toothbrush apparently had some obscure 4-bit microcontroller in it.

 

I would not be supprised if those cost 5ct a piece in blulk.

And an occasional single bit error also does also not seem too far fetched.

 

Some hobbyists have a fetish which makes them do all kind of stange stuff such as decapping chips with acid and reading out memory cells (with a capacitive probe ? )

One of those hobbyists might be able to help jou with your toothbrush.

 

If such a 4-bit uC has an extra pin (expensive ...) it could be that there is a jumper / solder bridge to use the same chip for "simple" and for "advanced" toothbrushes.

Maybe a bit of moisture seeped into your toothbrush and shorted it. But that's all guesswork.

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

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JC

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Could the slow speed be "burned up"--maybe they used to switch in a resistor, now shorted.  However, more likely they'd use PWM.   If a shorted resistor, you'd still have to push the button through the slow speed.

I had a car blower that exhibited speed strangeness due to a faulty resistor pack (had 4  speed resistors).  

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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If PWM, you'd still have to push the button through the slow speed.

"If such a 4-bit uC has an extra pin (expensive ...) it could be that there is a jumper / solder bridge to use the same chip for "simple" and for "advanced" toothbrushes.

Maybe a bit of moisture seeped into your toothbrush and shorted it. But that's all guesswork." seems more likely to me.

 

 

Four legs good, two legs bad, three legs stable.

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John_A_Brown wrote:

I'm not going to try and fix it or anything,

 

But you are going to take it apart and post a photo aren't you?

#1 This forum helps those that help themselves

#2 All grounds are not created equal

#3 How have you proved that your chip is running at xxMHz?

#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Brian Fairchild wrote:

John_A_Brown wrote:

I'm not going to try and fix it or anything,

 

But you are going to take it apart and post a photo aren't you?

Only when I've bought a replacement. Which will make me sad, as it's only about 17 years old, and I only just replaced the Nicad/NiMh(can't remember which) about a year ago.

OK, I might try to fix it...

Four legs good, two legs bad, three legs stable.

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Are these devices sophisticated enough to implement in firmware something like "after X charging cycles enable this_glitch"? 17 years ago it may have been a bad practice but not strictly ilegal to implement it, right?
 

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I think if an unscrupulous toothbrush manufacturer was going to do something like that, they'd have it kick in at four or five years. Unless you're suggesting I only brush my teeth a couple of times a week... Added to which, while a lot of folks seem to store their implements on the charger, I do wait until the battery is flat before recharging.

But see my original post wherein I referenced Apple. The idea of programmed obsolescence did occur to me.

Four legs good, two legs bad, three legs stable.

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My wife's electric toothbrush gave up the ghost last night so a new one has been purchased. And of course, the old one has been taken apart if only to dispose of the battery properly.

 

The chip doing brains duty is a TI MSP430F1232. That's a 16-bit chip folks.

#1 This forum helps those that help themselves

#2 All grounds are not created equal

#3 How have you proved that your chip is running at xxMHz?

#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Brian Fairchild wrote:
...That's a 16-bit chip folks.
Just what are you trying to say Brian? ;-)

"I may make you feel but I can't make you think" - Jethro Tull - Thick As A Brick

"void transmigratus(void) {transmigratus();} // recursio infinitus" - larryvc

"It's much more practical to rely on the processing powers of the real debugger, i.e. the one between the keyboard and chair." - JW wek3

"When you arise in the morning think of what a privilege it is to be alive: to breathe, to think, to enjoy, to love." -  Marcus Aurelius

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You bought the deluxe 16 bit toothbrush?   I saw a coupon for 30% off the 8 bit toothbrush.  

However, the store clerk said it would only run half as long before needing replaced.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Part of the toothbrush's post-mortem forensic analysis report :

   Why Microchip did not get the design win

  • ...

 

 

"Dare to be naïve." - Buckminster Fuller

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avrcandies wrote:
it would only run half as long before needing replaced.

 

Half?   Shouldn't that be 1/256th as long?

 

Jim

 

 

 

 

 

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https://duckduckgo.com/html?q=ee...

 

In EEVblog #284 Dave is yapping > 32 minutes over the contents of a Braun Toothbrush.

https://www.youtube.com/watch?v=...

 

The 4-bit uC is an EM668331 datasheet is @ 12 minutes into the video.

(4-bit @15min30s )

 

@ 13m58s:
The core is an EM6600 ...
Probably based of some derivative of something somewhere along the line and who knows, but anyway it's a single chip solution.

(I kid you not).

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

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You'd think for a toothbrush they'd certainly use an ARM processor, for synergistic effects.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Indeed. Or a hammer, maybe.

Four legs good, two legs bad, three legs stable.

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Hmmm, not only a '430 but also a serial flash chip.

 

#1 This forum helps those that help themselves

#2 All grounds are not created equal

#3 How have you proved that your chip is running at xxMHz?

#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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The only thing missing is LoRa to talk to the tooth fairies.

 

What kind of functionality would justify such an amount of hardware in a toothbrush?

( Brand / Model?)

 

Could it be for planned obsolesence?

That it starts draining the batteries after a year of use just to wreck them?

 

The batteries of my old Braun are as good as dead.

I haven't opened it yet because I do not have a replacement laying around.

I do know that different models have different batteries inside them.

I may try to replace the old (probably 2 NiMh cells) with an 18650.

 

One of the anoying things of those tooth brushes is that the battery is deemed non-user replacable.

It is also not possible to buy a new toothbrush without a new charger.

Those potted chargers never die.

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

Last Edited: Tue. Jan 23, 2018 - 10:48 AM
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Paulvdh wrote:

What kind of functionality would justify such an amount of hardware in a toothbrush?

( Brand / Model?)

 

Braun/Oral B model 3745

#1 This forum helps those that help themselves

#2 All grounds are not created equal

#3 How have you proved that your chip is running at xxMHz?

#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Can we assume you've tried the obvious repair i.e. "give it a power cycle" then see if it still misbehaves ?

 

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Soon, toothbrushes will be running Linux...

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How can a 17 years old thing have parts that's only 10 years old :)

 

 

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I was the one who said 17 years old(and that was a guess).

I'm not the one who has taken the brush apart and examined the parts.

 

Four legs good, two legs bad, three legs stable.

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sparrow2 wrote:
How can a 17 years old thing have parts that's only 10 years old :)

Two different examples:

Original 1-speed brush - Owned by John_A_Brown

Other complete failure & taken apart: Owned by  Brian Fairchild 's wife. (#10)

 

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Ups!

Sorry

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El Tangas wrote:

Soon, toothbrushes will be running Linux...

Let's hope it's Linux Mint.

Four legs good, two legs bad, three legs stable.

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N.Winterbottom wrote:

Can we assume you've tried the obvious repair i.e. "give it a power cycle" then see if it still misbehaves ?

 

No, as that would involve disassembly and desoldering the battery. Maybe when I replace it, which is overdue, as the soft grip rubber is perishing/dissolving.

Four legs good, two legs bad, three legs stable.

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John_A_Brown wrote:

...the soft grip rubber is perishing/dissolving.

 

Which is exactly why we had to change my wifes.

#1 This forum helps those that help themselves

#2 All grounds are not created equal

#3 How have you proved that your chip is running at xxMHz?

#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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While being a bit curious as of the use of an '430 in a toothbrush I bumped into "toothbrushbattery.com"

Looking at their prices there is quite a market to replace those non replacable batteries, complete with solder tabs.

 

https://toothbrushbattery.com/gu...

 

The most absurd yet is however: the Braun Oral-B 9900

I've seen at least 3 websites where they want USD170 for the thing.

It's a toothbrush for crying out loud !!!

The most distubing fact for me is that there is apparently a big enough group of people who are willing to pay such a price for a toothbrush.

 

Mine is a model 4729 and according to toothbrushbattery it should have an tms430F1122 (see pic below).

But I just opened it and there is a TMS430G2332 inside. No flash chip. The 8-legged thingie is probably the MOSfet ( Multiple legs shorted on the pcb).

My toothbrush also does not have any complex functions. Just a single momentary button for on/off, a timer wich momentarily stops the motor, 2 leds and a charge circuit.

 

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

Last Edited: Tue. Jan 23, 2018 - 12:43 PM
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My toothbrush uses so little power it does not need a battery. It is powered by breakfast, lunch and dinner.

 

Ross McKenzie ValuSoft Melbourne Australia

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Brian Fairchild wrote:

John_A_Brown wrote:

...the soft grip rubber is perishing/dissolving.

 

Which is exactly why we had to change my wifes.

 

When I read this, why did I think you got new wives?surprise

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El Tangas wrote:

 

Soon, toothbrushes will be running Linux...

 

 

Let's hope it's Linux Mint.

Probably the toothbrush already has an operating system, likely Windows Embedded CE, and the "faulty" toothbrush will spring back to life as soon as the current Windows Update is done downloading and installing...

 

JC

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dksmall wrote:

Brian Fairchild wrote:

John_A_Brown wrote:

...the soft grip rubber is perishing/dissolving.

 

Which is exactly why we had to change my wifes.

 

When I read this, why did I think you got new wives?surprise

That's why those apostrophes are so important...

 

Four legs good, two legs bad, three legs stable.

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John_A_Brown wrote:
That's why those apostrophes are so important...

Let's eat Grandma!

 

---

 

Let's eat, Grandma!

My digital portfolio: www.jamisonjerving.com

My game company: www.polygonbyte.com

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Jamison wrote:

John_A_Brown wrote:
That's why those apostrophes are so important...

Let's eat Grandma!

 

---

 

Let's eat, Grandma!

... and the commas.

 

Ross McKenzie ValuSoft Melbourne Australia

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Paulvdh wrote:
The most distubing fact for me is that there is apparently a big enough group of people who are willing to pay such a price for a toothbrush.
They are presumably the same people who buy Apple products and also things like this piece of nonsense:

 

Image result for dyson hair dryer

 

For £299/$399 I'd want it running Linux, fitted with GPS, bluetooth and a decent sized LCD display on which I could get my texts and emails!!

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Ok, I had to do a reverse image search to find what is that... I'm off to youtube to see some vids... https://www.youtube.com/watch?v=...

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Oh I thought everyone here would already be aware of the madness that is Dyson? In their TV adverts for this cripplingly expensive hairdryer it even makes a point of saying that there's a "clever micro" in there sensing the temperature 50 times a second or something?