How Jawbone UP Works

If you were to strip the rubber coating off the UP, you would find a strip of steel springs that keep the wristband's shape. Mounted on the strip are the UP's electronic components. These include a lithium-ion battery, a motion sensor and a vibration motor. On one end of the steel spring you'll find the 3.5-millimeter jack. On the other end is a button that lets you change the UP's mode of operation.

The battery provides the power and can last several days. Recharging requires you to plug the UP into a USB cable with a headphone-jack adapter.

The motion sensor detects changes in acceleration. Acceleration has two components: speed and direction. If an objection in motion experiences a change in either speed or direction, it has a change in acceleration. Motion sensors detect these changes through tiny electromechanical elements.

A basic solid-state accelerometer looks like a sandwich. The outer layers are capacitance plates carrying an electric charge. In between the plates is a weight suspended between them. When the entire sensor is still, the weight rests between the two plates. But in motion, forces act on the weight, which will move toward one plate and away from another. As the weight draws closer to one plate, its capacitance increases. The other plate experiences a decrease in capacitance. The sensor registers this as movement.

As you move over time, the weight continues to shift, causing more changes in the capacitance of the plates in the sensor. The sensor analyzes the data and converts it into information useful to you, including how many steps you've taken and an estimation of the number of calories you've burned.

The UP wristband doesn't have a display. To get a look at all that precious fitness data, you'll need to connect the UP to an iPhone, iPad or iPod touch -- as of this writing, an Android app is in development. Plugging the TRS plug into your device's headphone jack does the trick. But how can a headphone plug transmit data?

One of the most common uses of the 3.5-millimeter jack is for headphones. But that's not the only type of data that can travel through a TRS plug. The TRS plug is made up of three conductors called the tip, ring and sleeve. When plugged into an appropriate jack, these three conductors make contact with three contact points. This allows for the transfer of data in the form of analog signals.

Data can travel in either direction along a TRS plug. When you plug in your headphones, data from your device travels through the plug up the wire to the speakers in your headphones. The speakers convert the data from electricity into sound. With the Jawbone UP, data travels from the sensor to the TRS plug into your device. The app accepts the data and translates it into a form that's easy to understand such as how many steps you've taken or calories you've burned.

The app also lets you pair your device's abilities with the UP. For example, the iPhone has a GPS receiver inside it. When going for a jog outside, you can set your app to use the iPhone's GPS receiver to track your position during an activity. When finished, you can pair your UP with the iPhone and the app combines data gathered by the motion sensor in the UP and the GPS receiver in the iPhone.

Through the app, you can elect to share your progress with others via the Jawbone UP site, or keep it all to yourself. The app can also set challenges for you to conquer throughout the day. The vibrating motor in the UP lets you set an alert -- sit still too long and the UP will begin to vibrate, signaling that it's time to get a move on.

In sleep mode, the UP registers more subtle movements. In essence, it acts like an actimetry sensor. These sensors register a person's movements as they rest and sleep. The UP system analyzes the data by processing it through proprietary algorithms. The result is a record of whether you slept like a log or tossed and turned all night long. Sleep and fitness are related -- a good night's sleep can help you reach fitness goals faster.

You can enter information about the food you eat with the UP app. Keeping a food diary is a good idea for anyone who wants to lose weight. You can see at a glance if you're on track to shed those extra pounds -- or put on more muscle.

Studies show that people who make the effort to record their meals are more likely to lose weight and keep it off. Scientists at the Kaiser Permanente Northwest Center for Health Research conducted a weight loss maintenance trial in 2008 and discovered that subjects who kept a record of their meals and activities lost an average of 12.8 pounds (5.8 kilograms) over six months [source: Hollis, et al.].

You can do this without a special app or device, but it's a lot more work. For some, a gadget or piece of software might help break down the barrier between getting up and taking action or slacking off on the couch.

The Jawbone UP app doesn't just keep track of the calories you've eaten. It will also poll you and ask how you feel after each meal. Reflecting on how you feel may guide you to make better choices in the future.

The app can provide you with eating challenges. You're not going to find yourself gorging on a seemingly endless supply of pies. Instead, you may have to avoid processed foods for a week or two or make sure you drink eight glasses of water each day. Some challenges even let you contribute to charitable causes indirectly -- completing the challenge means Jawbone and its partners will donate money toward a particular charity.

Ultimately, the purpose of keeping track of your meals is to see how many calories you consume each day versus the number you burn through activities. Burn more calories than you consume and you're on the way to weight loss.

In late 2011, Jawbone had a problem. Customers who bought UP wristbands began calling the company to report gadget failures. According to Jawbone, the problem was with some capacitors inside the device.

A capacitor stores electrical energy. That sounds a lot like a battery, but a capacitor has a different function. A battery releases energy in a steady stream of electrons as a result of a chemical reaction. A capacitor simply stores electrons -- it can't generate them on its own. But unlike a battery, a capacitor can also release all its stored electrons at once.

A basic capacitor consists of two conductive plates with a nonconductive material called the dielectric between the two. In a simple circuit, one plate connects to the negative end of a battery -- this is the end of the battery that generates electrons. This means the plate gains electrons and as a result gains a negative charge. The other plate connects to the positive end of the battery. Electrons from this plate travel to the battery, leaving the plate with an overall positive charge.

Negatively-charged particles are attracted to positively-charged surfaces, creating a difference in potential. When the voltage across the capacitor equals that of the voltage applied by the battery, current ceases to flow through the circuit. Though the electrons in the negatively charged plate are attracted to the positively-charged plate, they can't move across the barrier of the nonconducting dielectric. Incorporating the capacitor in a new circuit by flipping a switch allows the capacitor to discharge the energy stored in it as electrons redistribute and the capacitors reach a neutral state.

In 2011, several UP wristbands suffered capacitor failures. Some had trouble holding a charge, which meant that the wristbands couldn't track data accurately. Others couldn't hold a charge at all, leaving the wristband bricked or useless. The problem was so widespread that Jawbone CEO Hosain Rahman issued a letter on the Jawbone Web site explaining the company would refund any customer's purchase. He reaffirmed the company's desire to ship products that worked as advertised and thanked customers for their support [source: Jawbone].

The real problem for Jawbone might not be faulty capacitors. The gadget market appears to be flooded with fitness devices. Companies like Motorola Mobility have entered the fray along with startups like Striiv. Is there a place for an iOS-specific fitness accessory? Or will other gadgets push Jawbone's UP system to the side? In the weight-loss gadget world, it's survival of the fittest.

The Jawbone UP is an intriguing device. It's extremely portable. It's water resistant -- you can even wear it in the shower. There's no real reason to take it off other than to charge it or synchronize your data. That might give the UP an advantage over other devices that are easier to misplace. But if you don't own an iOS device, the UP is just a fashion accessory. As someone who has tried a few different gadgets designed to keep me active and in shape, I'm curious to see if the UP can hack it in the long run.

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