Tools Featured in this Teardown

Introduction

Here at iFixit, we promote only the healthiest of lifestyles. We eat our vegetables at least once per week, and we never eat pizza two days in a row (unless it's leftovers, of course). One might go so far as to call us health freaks. We would not argue.

But we are iFixit, so of course we're sacrificing our fitness ambitions for science. We ripped into Fitbit's newest pedometer/heart rate monitor/sleep tracker wristband. What kind of a diet helped this thing fit into its tiny jacket? We're about to find out.

Check out Instagram if you're interested in getting a behind-the-scenes look at iFixit. Food, gnomes, and fancy filters not your thing? Get a healthy dose of fighting eWaste on Twitter and Facebook.

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

Image 1/3: Two adjustable wristbands: one large, one small Image 2/3: Wireless sync dongle Image 3/3: Charging cable
  • So many goodies in one package! The Fitbit Flex comes with the following:

    • Two adjustable wristbands: one large, one small

    • Wireless sync dongle

    • Charging cable

  • The Flex tracker sports some cool tech specs, too.

    • Bluetooth 4.0 syncing

    • Memory to store 30 days of data

    • 5-day battery life

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Image 1/3: Although it seems like a small consideration, we appreciate how easy it is to separate the electronics from the wrist strap—the component most likely to wear out. Image 2/3: Although it seems like a small consideration, we appreciate how easy it is to separate the electronics from the wrist strap—the component most likely to wear out. Image 3/3: Although it seems like a small consideration, we appreciate how easy it is to separate the electronics from the wrist strap—the component most likely to wear out.
  • With less effort than peeling an orange, we peel the Fitbit Flex tracker out of the flexible wrist strap.

  • Although it seems like a small consideration, we appreciate how easy it is to separate the electronics from the wrist strap—the component most likely to wear out.

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Image 1/2: The Flex may be slightly larger than a half dollar (though smaller than half a dollar bill), but it will cost you 200 of them. Image 2/2: If anyone pays for a Fitbit Flex with half dollars, we would love to hear about it.
  • Normally we would compare the device to other similar devices. Unfortunately, we don't really have much to compare the Flex to. How about a half dollar?

  • The Flex may be slightly larger than a half dollar (though smaller than half a dollar bill), but it will cost you 200 of them.

    • If anyone pays for a Fitbit Flex with half dollars, we would love to hear about it.

  • The back of the Flex reveals the model number, FB401, and provides a nice insertion arrow. It's not quite disassembly information, but it's something, right?

Please can you give me the correct measurements for the little fitbit flex chip?

Cant't find them during your teardown.

Thanks

Anne Labs - Reply

Image 1/3: For the record, the Flex claims to be water-tight up to 10 meters, or 264 simultaneous Gatorade showers. Image 2/3: This tiny gizmo fits snugly in its USB charger when its lithium-polymer battery needs juice. Image 3/3: Not to worry, it won't take the place of your smartphone on the charger each night—this little gadget has a reported battery life of 5 days.
  • The first things we notice on the Flex are the waterproof contacts. This is good news for those who might be sweating while wearing, or tearing down, the Flex.

    • For the record, the Flex claims to be water-tight up to 10 meters, or 264 simultaneous Gatorade showers.

  • This tiny gizmo fits snugly in its USB charger when its lithium-polymer battery needs juice.

    • Not to worry, it won't take the place of your smartphone on the charger each night—this little gadget has a reported battery life of 5 days.

i lost the cable charger, anybody know the 3 pin (positive negative) for fitbit

Andrew - Reply

Have you found out? Wish ifixit tore down the motherboard.

Peter -

where is the small hole for a reset I can't find it. Any alternatives to the charging situation

Nita Ellis - Reply

The reset hole is on the charging adapter, not the device itself.

odaiwai -

To answer for charging purposes. The center pin is positive. And while looking at the led side of the flex and the pins towards you, the right pin is ground.

theabsolut1 - Reply

Thank you! It was very helpful to have such a precise description of the pins.

facebook20dllahr -

How many volts? 5v? what is the third pin for?

Mariano Adolfo Nardi - Reply

3 Volts worked for me, also it looks like a button battery which is typically a 3 V bat

Richard Vaughn - Reply

Image 1/2: Around here, we're big fans of [http://www.dozuki.com|Dozuki]. We're also big fans of [product|IF145-165|dozukis|new_window=true]. When saw comes to gadget, you know it's a teardown. Image 2/2: Remember that teardowns are for fun and should not be followed as disassembly instructions. Please do not cut into your device with a dozuki.
  • With no visible point of entry, we figure the path to victory can be carved with judicious application of sharp tools.

  • Around here, we're big fans of Dozuki. We're also big fans of dozukis. When saw comes to gadget, you know it's a teardown.

  • Remember that teardowns are for fun and should not be followed as disassembly instructions. Please do not cut into your device with a dozuki.

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Image 1/3: Next out is the Bluetooth antenna, used for communicating with devices and the accompanying dongle. Image 2/3: Oops! We appear to have a tiny hitchhiker; that's a piece of the motherboard hanging on to the antenna. Image 3/3: To those of you following along at home: you don't need to chop up your PCB.
  • Our first extraction: the light guides for the LEDs that pass for a display on this slim, dare we say emaciated, unit.

  • Next out is the Bluetooth antenna, used for communicating with devices and the accompanying dongle.

  • Oops! We appear to have a tiny hitchhiker; that's a piece of the motherboard hanging on to the antenna.

    • To those of you following along at home: you don't need to chop up your PCB.

      • P.S. Don't follow along at home.

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  • Pulling components out through the top of the Flex worked for a little while, but it's time to get to the good stuff.

  • Using our handy rotary tool, we cut through the plastic casing of the Flex tracker.

  • Well hello there, Rico Suave! Peeling back the Flex's stylish plastic jacket reveals the components we've been looking for.

  • Repairability update: This little guy is never, ever, ever going back together.

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Image 1/3: Small and encased in a thin sheet of metal tape, the battery is soldered to the motherboard. By this point, a replaceable battery is the least of our worries. Image 2/3: We're getting some [http://www.youtube.com/watch?v=Eab_beh07HU|good vibration|new_window=true][http://www.youtube.com/watch?v=-eSN8Cwit_s|s|new_window=true] from the prominent vibrator that functions as an alarm. Image 3/3: We're getting some [http://www.youtube.com/watch?v=Eab_beh07HU|good vibration|new_window=true][http://www.youtube.com/watch?v=-eSN8Cwit_s|s|new_window=true] from the prominent vibrator that functions as an alarm.
  • The main board slides right away from the contact pins. Now we can get to the juicy bits.

  • Small and encased in a thin sheet of metal tape, the battery is soldered to the motherboard. By this point, a replaceable battery is the least of our worries.

  • We're getting some good vibrations from the prominent vibrator that functions as an alarm.

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  • This is how your vibrator works in your Fitbit Flex.

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Image 1/3: The NFC tag enables a tap launch of the Flex tracker's associated mobile app with "select NFC-enabled Android devices." Image 2/3: [http://youtu.be/96kwILL35ig?t=13s|"It's like magic."|new_window=true] Image 3/3: This little guy looks like a likely candidate for the NFC controller.
  • Stuck right on to the front of the board we find a near field communications (NFC) antenna.

  • The NFC tag enables a tap launch of the Flex tracker's associated mobile app with "select NFC-enabled Android devices."

  • This little guy looks like a likely candidate for the NFC controller.

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Image 1/2: STMicroelectronics [http://www.st.com/web/catalog/mmc/FM141/SC1169/SS1295/LN962/PF252048?s_searchtype=partnumber|32L151C6|new_window=true] Ultra Low Power ARM Cortex M3 Microcontroller Image 2/2: Nordic Semiconductor [http://www.nordicsemi.com/eng/Products/Bluetooth-R-low-energy/nRF8001|nRF8001] Bluetooth Low Energy Connectivity IC
  • The motherboard flexes to show us what it's repping:

    • STMicroelectronics 32L151C6 Ultra Low Power ARM Cortex M3 Microcontroller

    • Nordic Semiconductor nRF8001 Bluetooth Low Energy Connectivity IC

    • Our best guess is that this is the accelerometer IC

    • Charger IC: TI BQ24040

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Image 1/3: Plastic aside, we get to the goodies. Image 2/3: We quickly free the dongle board from the metal casing of the USB plug. Image 3/3: We quickly free the dongle board from the metal casing of the USB plug.
  • We just couldn't keep our scalpels to ourselves, so we ripped into the Flex's dongle as well.

  • Plastic aside, we get to the goodies.

  • We quickly free the dongle board from the metal casing of the USB plug.

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Image 1/2: Texas Instruments [http://www.ti.com/lit/ds/symlink/cc2540.pdf|CC2540F128|new_window=true] 2.4 GHz Bluetooth Low Energy SoC Image 2/2: On the contact side:
  • Enough loligagging, let's cut to the chase. This diminutive USB board houses all of the hardware needed to communicate with the Flex — and your computer:

    • Texas Instruments CC2540F128 2.4 GHz Bluetooth Low Energy SoC

  • On the contact side:

    • BLE Antenna

    • USB connection contacts

Why a second TI BLE controller in the USB dongle when there is already a Nordic Semi BLE controller on the motherboard?

Lee Courtney - Reply

Never mind. After looking at the use cases on the Fitbit website of course one needs BLE in the *wireless* sync module. I was confusing with the USB dongle.

Nice teardown, wish you had ID'd other components on the motherboard.

Lee Courtney - Reply

What an awesome teardown, it's a shame though that they make this thing basically disposable.....at 99$ + tax....I guess I can't complain too bad though, it did last a little over 1 year ;) And yes, I showered, and went swimming/diving in an 8 foot deep pool with mine on many ocassions....

My "first" Flex only lasted about 4 months though.....would anyone be interested in tearing these now "broken" units down? LOL....it really shocked me, that Fitbit did NOT want the old defective"Flex" tracker back, when they sent me the replacement.....since this is really not repairable at all ;) They simply told me to drop it off at a local "electronics recycler" (luckily that would be my local dump!) but yea, just chiming in. I enjoyed this ;) Came here to see if there's a way of "fixing" it lol.....but no such luck haha

hackerfool - Reply

The batteries tend to not hold much charge around the time the warranty runs out. If there was somewhere you could get a replacement, a few minutes with a hot air gun to take it apart and solder a new battery in would get it working again.

James Van Damme -

Image 1/2: Solid waterproofing, no moving parts, and lightweight construction make the Flex a very durable device, with the potential to last a long time. Image 2/2: The wrist strap is similarly constructed and can be easily replaced.
  • Fitbit Flex Repairability Score: 2 out of 10 (10 is easiest to repair)

    • Solid waterproofing, no moving parts, and lightweight construction make the Flex a very durable device, with the potential to last a long time.

    • The wrist strap is similarly constructed and can be easily replaced.

    • It's impossible to open the device without destroying it or at least compromising the waterproofing, making internal repairs infeasible.

    • The Flex's inaccessible (and non-replaceable) battery limits the life of the device.

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15 Comments

唔,里边似乎不太精致呀。

Jam - Reply

i also lost the cable charger, anybody know the 3 pin (positive negative) for fitbit. Any universal charger I can use?

Victor Hugo Garcia Hernandez - Reply

look at the enlarged image... Left Pin is connected to the housing of the vibrator - this tells me its GND or Neg, center pin has a much thinner track on the PCB i would call it Data, right pin therefore looks like VCC+.

Sarah -

i also lost the cable charger, anybody know the 3 pin (positive negative) for fitbit. Any universal charger I can use and how?

Victor Hugo Garcia Hernandez - Reply

Have you found out? Wish ifixit tore down the motherboard.

Peter -

The wifey lost her fitbit flex charger and there was no time to order a new one before ourtrip. For those of you wondering about the pinouts for the flex below are two pictures of how I managed to charge her using a couple of paperclips and a chopped USB cable.

http://members.shaw.ca/kroker/fitbit_fle...

http://members.shaw.ca/kroker/fitbit_fle...

Paul - Reply

Super useful pictures. Thank you !

alexanderkarailiev -

Thank you! Very helpful pictures.

facebook20dllahr -

Does a fitbit work by radio frequency waves like a cell phone does? How does this sync with your cell phone?

Morticia - Reply

it uses Bluetooth, which does in fact use radio frequency of 2.4 GHz,. However, unlike regular cell phones which also uses 2.4 GHz Bluetooth uses a radio technology called frequency-hopping spread spectrum.

dna -

Just so you all are away you can dissemble the flex without fully destroying its casing, make a small but deep incision with a sharp blade around the led display cover just enough to break the adhesive used to seal the component from there you can gently but firmly pull the board/speaker/antenna from the casing leaving behind an empty shell. Mine recently stopped charging so I decided to have a bit of fun before I seen this teardown. Needless to say a little superglue with a new battery and I've got a functional fitbit flex again. Hard part will be finding a replacement battery....

cyberstudm - Reply

That battery looks like it could be useful for mini-planes etc, ie using a single pager motor.

I have actually tried using the one from Bluetooth headsets and this does work so perhaps old broken Fitbits could be a source of replacement parts?

Andre - Reply

Have you been able to source where that battery is available? I need many small batteries like that and cant find one anywhere.

Philip Barker -

Im not sure why you guys sawed it apart, the cap by the led is held in place with something similar to hot glue, a few seconds in front of a hot air source and it comes out pretty easily, the circuit pack is also held in place with some sort of hot glue. My wife wore hers into the ocean and it quit, a soak in rubbing alcohol and drying it out restored it to working order.

CalebG - Reply

Awesome teardown. So, where is all the data stored? I mean does it store the totaled/summary data or all the raw data is stored?

Keeran - Reply

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