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  • Cell Phone Design

  • The seven basic constraints that shape a mobile phone

  • series 3 engineerguy videos

  • Nothing illustrates engineering design better than a mobile phone.

  • In fact, a definition of engineering might be something like

  • "design with real world contraints."

  • Here's the seven major constraints that govern the choices made by an engineer in designing a cell phone.

  • The essential trade-off in any cell phone is compactness versus usability.

  • We want a small phone, but we also want one that fits our bodies. ho 10 00:00:31,000 --> 00:00:33,000 Here's three solutions.

  • A hinge.

  • The classic flip phone - put a hinge in and change the size and it allows you to have larger keys.

  • You can also see this same idea in slider keyboards.

  • Second, you can do what they do on this phone - a Blackberry - and maximize available space by using very tiny keys.

  • And, you can use software.

  • This is my android, the phone I use everyday

  • and I've added to it a clever littled keyboard designed for small devices.

  • I can spell my name just be doing this.

  • Very clever isn't it.

  • Next, emotions affect the design of a cell phone.

  • You don't see these too much today, but the flip of this now nearly vintage phone

  • resonates deeply in the psyche of someone my age.

  • I grew up watching Captain Kirk grab his communicator and bark a command.

  • Beam me up Scotty.

  • I'm sure phones today resonate in some way with video games or popular movies.

  • Now, next, in making a compact design an engineer considers energy.

  • In the twenty years or so that I've been using a cell phone they've shrunk.

  • Hold on.

  • Look at how huge this vintage "brick" phone is from the 1980s.

  • This isn't even one of the first ones:

  • Its one of the later ones called an "ultra classic II", slightly smaller than the first phones.

  • It weights just over a pound and seems to be mostly battery.

  • It uses a nickel-cadmium one.

  • Compare it to this lithium ion from a more modern phone.

  • Now batteries shrunk because they got better

  • we have greater energy density now

  • but likely more important is the move from

  • analog to digital signaling,

  • and a movement of much energy-draining computation

  • from the phones themselves to the towers.

  • The next constraint also helped reduce battery size.

  • Old cell phones had brick sized batteries partly because it took a lot of power to reach a cell phone tower;

  • but today we have such a density of towers that we don't need as much energy to reach one.

  • The increase in towers has made this [antenna] a nearly endangered species.

  • For this RAZR this is the closest indication of an antenna:

  • Its a rubber cover for the for the external antenna connector, used during testing of the phone at the factory.

  • The actual antenna is inside underneath one of the plastic parts of the case of the phone.

  • Now, this doesn't work as well as a huge external one,

  • but that's the the trade-off between compactness and usability I mentioned earlier.

  • Now, another reason for the phones compactness is plastics.

  • If we didn't have plastics this phone would be much larger and more expensive.

  • Take just this "latch" imagine how bulky some kind of clasp would be.

  • The fact that this plastic gives a little bit and

  • pops back in to place makes this simple, small fastener possible.

  • The phone's designer needed a deep knowledge about how plastic behaves

  • so that it could be used thousands of times without wearing out.

  • The insides - the way a phone operates - reflects yet a sixth design criteria.

  • On most modern cell phones you'll something called Enhanced or E911.

  • In an emergency an operator can locate the phone to within several hundred feet.

  • Typically it doesn't use true global positioning,

  • but instead "assisted GPS" in that it uses the location of cell phone towers to triangulate.

  • Now, this is fraught with all types of privacy issues.

  • Lastly, we need this phone to quickly change the volume

  • because as a culture we've decided that there are times when our cell phones shouldn't ring.

  • And so we can adjust the ring tone volume easily.

  • I'm Bill Hammack, the engineer guy.

  • Hi, how did you get this number.

Cell Phone Design

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