Tools Featured in this Teardown

Introduction

The FitBit One is part of the family of fitness devices from FitBit Inc, designed to track your movement throughout the day and display the data via a website dashboard.

FitBit One is a wearable device that keeps track of the number and rate of steps you take and stairs you climb, and it uses this information to calculate various metrics like distance covered and calories burned. The device periodically sends the data it gathers to FitBit's servers via wireless communication with internet connected smartphones, iPads, or a PC with dongle.

There are a number of interesting features that warrant the teardown. It has a rechargeable battery that should power the device for about two weeks. It has a haptic alarm for time of day reminders. It has a bright LED display that shows the current statistics, and it is claimed to be sweat proof and rain proof, but not water proof. it also claims to remember minute-by-minute movement stats for up to seven days, and a summary of movement data for much longer.

Time to open it up and see what's inside this mighty machine.

This teardown is not a repair guide. To repair your Fitbit One, use our service manual.

Image 1/2: Inside you can see a number of large cut outs in the rear of the plastic casing. Image 2/2: Note the small pinhole in the metal backplate that aligns with the rubber sealed hole in the plastic casing - more on that later.
  • Removing the metal backplate is simple. This is just stuck on with some flexible glue. So prise something under and off it pops.

  • Inside you can see a number of large cut outs in the rear of the plastic casing.

  • Note the small pinhole in the metal backplate that aligns with the rubber sealed hole in the plastic casing - more on that later.

  • There is also a very small ground out area inside the metal backplate that appears to align with the rotating mass of the vibrator.

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Image 1/2: There are plastic clips at each end that are easy to cut through inadvertently if you go too deep. Image 2/2: The front now lifts away cleanly.
  • The plastic casing is made up of two parts stuck together, so using a scalpel carefully cut along seam

    • There are plastic clips at each end that are easy to cut through inadvertently if you go too deep.

  • The front now lifts away cleanly.

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Image 1/2: Above the display, running down the right hand side of the device front, is the [http://en.wikipedia.org/wiki/Bluetooth_low_energy|BLE] antenna. Image 2/2: Lifting the LCD glass just results in destroying it, and there is nothing interesting underneath anyway.
  • Inside the front cover you see the LCD display, attached by ribbon cable and stuck firmly onto the PCB.

  • Above the display, running down the right hand side of the device front, is the BLE antenna.

  • Lifting the LCD glass just results in destroying it, and there is nothing interesting underneath anyway.

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Image 1/2: Notice how the battery is supported on stand-offs from the rear of the PCB. Image 2/2: The battery is held in place with a small foam block adhering to the battery and PCB.  Cut that away and the battery lifts off.
  • The PCB lifts out from the back of the plastic housing easily.

  • Notice how the battery is supported on stand-offs from the rear of the PCB.

  • The battery is held in place with a small foam block adhering to the battery and PCB. Cut that away and the battery lifts off.

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Image 1/2: The [http://en.wikipedia.org/wiki/System_on_a_chip|SoC] has a [http://en.wikipedia.org/wiki/Qr_code|QR code] sticker, likely for inventory control, so take that off to see what we have underneath. Image 2/2: You can also see the spring-loaded paddles at the bottom of the PCB that connect to the device charging pins.
  • Now we get to see some more interesting parts.

  • The SoC has a QR code sticker, likely for inventory control, so take that off to see what we have underneath.

  • You can also see the spring-loaded paddles at the bottom of the PCB that connect to the device charging pins.

  • The power control module for the battery is wrapped up near the battery terminals.

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Image 1/2: [http://www.st.com/web/en/catalog/mmc/FM141/SC1544/SS1374/LN1041|STMicroelectronics STM32L 151] ARM-based SoC microcontroller Image 2/2: [http://www.nordicsemi.com/eng/Products/Bluetooth-R-low-energy/nRF8001|Nordic Semiconductor nRF8001]Bluetooth chip

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Image 1/2: In turn, the inside of the plastic cover presses onto a foam collar around the altimeter on the PCB. Image 2/2: This makes the device sweat proof, but not water tight.
  • The air pressure hole, required for the altimeter, is protected by a piece of paper held in place by a foam collar.

  • In turn, the inside of the plastic cover presses onto a foam collar around the altimeter on the PCB.

  • This makes the device sweat proof, but not water tight.

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Image 1/1: Looks like a tidy, well-designed bit of tech!
  • Too bad the display was damaged during teardown.

  • Looks like a tidy, well-designed bit of tech!

  • Conclusion is that the FitBit One is not an easily repairable device.

    • The device is not designed to be opened, so you will do some damage by cutting it open

    • Taking things apart will compromise the water resistance of the device, and the LCD display is easily broken by any flexing or attempts to modify.

Awesome! I've always wanted to see inside one of those.

Kyle Wiens - Reply

i don't this particularly interesting because there is nothing that I can apply to fix or modify. So, I'm glad to just see it and move on. It's more interesting to tear down a LED TV to see the modular components and try to diagnose the problem.

oakland1000 - Reply

Took mine apart when it wouldn't come on at all, went for a dip in the beach with it clipped to my pants so I thought that was why. Surprised I was when the inside was immaculate! (I also washed it in the machine twice and dropped it in the sink with running water once) Anyway, did some prodding and poking under my phone camera magnifier app, plugged it into the charger and it came on! The battery won't last through a day again though. Anyone know where I can get a battery to fit?

Godfrey Harry - Reply

Tim Ellison

Member since: 11/28/2013

231 Reputation

1 Guide authored

14 Comments

Are there any markings indicating the controller interface for the LED display? Its a nice display, and I'd be curious if the module in my broken Fitbit could be repurposed.

Andrew Villeneuve - Reply

My Fitbit went through the clothes washer attached to my jeans. When it came out I was amazed it was still working, but after 2 days the display went blank, and it was dead to the world. I tried unsuccesfully to dry it out in rice for a week, but that didn't help at all. I then took the decision to carefully open it as in this guide. I found quite a lot of sulphate corrosion at various places on the board, plus some water droplets inside the case. I cleaned the board with an ear bud dipped in methylated spirits to remove the corrosion, and I dried the water drops carefully with hair dryer. After gluing it together, and charging, it is working perfectly again - I guess not as water tight as before, but I can live with that - so long as it doesn't go through the washer again :P

wayne - Reply

Could anyone tell me what kind of tools I should use to remove the metal back? I spent some time but did not work it out. Thanks.

Elias - Reply

My Fitbit One fell face down during a wintry mix and drizzle and when I found it, it wasn't working. I put it in a bag of rice for a few hours but it didn't work. I opened it up and everything was remarkably clean and dry, but so far no success in resuscitation!

Chris - Reply

@Elias, I used a heavy duty razor blade utility knife slipped under the end by the switch, and twisted gently to not damage the finish along the edge. Patience to wait while the glue stretches and releases is key. The same knife along one side of the case was enough to open that as well.

Unfortunately in my washing machine induced case, the corrosion in the battery charging circuit appears to be fatal.

jadeters - Reply

Mine recently stopped worked.. opened it and found one of the standoffs for the battery loose and intermittently touching the circuit board causing it to short out.. after removing it and glueing it back together, all seems to be like it was..

kerwinlewis - Reply

I followed these instructions and the metal back plate took a lot of effort and time to get off. Once that was off the rest came apart easily. I put my Fitbit through the wash and it would work. I found corrosion and cleaned it up with some rubbing alcohol and put the Fitbit back together and it works again! Thanks for the instructions!

Dennis Bird - Reply

Just fixed mine after a washing in the machine, the black wire on the battery had corroded through, bared back and resoldered, now working fine.

The symptoms were, no life until connected to usb charger then battery level shown as full, and fitbit 6.06 displayed for a few seconds.

John Caldicott - Reply

My Polymer Li-Ion Battery has swollen to the point that the back pop off. Looks like gas in the battery like it is going to pop. . Can I use a pin to let the gas escape, if it is gas? The case will not close with the battery swollen the way it is.

Mike Comrie - Reply

why would you not start with the conclusions so ppl know what they are getting themselves into?

Kevin G - Reply

Which one of connector is positive? or does not matter!

Is it possible to charge 5V USB cable... I Lost Charging Unit ;-((

Thanks in Advance...

Adem AYDIN

ademaydin - Reply

When looking at the back of the FitBit One from outside the case, the left hand side is negative and the right hand side is positive.

roughana - Reply

Now, can we get a replacement battery? Or hack some other tiny lithium battery in?

As above mine has no life until connected to usb charger then battery level is shown as full, and fitbit 6.06 is displayed for a few seconds.

Bryce Nesbitt - Reply

What voltage is that battery? What size? Small coin cells in that range are available at DigiKey....

Bryce Nesbitt - Reply

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