Schedule

Schedule

Tuesday, March 3

1425430800 All About Android

Wednesday, March 4

1425486600 FLOSS Weekly
1425492000 Tech News Today
1425495600 Windows Weekly
1425502800 This Week in Google
1425513600 Tech News 2Night
1425515400 Android App Arena
1425520800 Ham Nation

Thursday, March 5

1425578400 Tech News Today
1425582000 Know How...
1425587400 Marketing Mavericks
1425592800 Home Theater Geeks
1425600000 Tech News 2Night
1425601800 The Giz Wiz

Friday, March 6

1425664800 Tech News Today
1425668400 This Week in Law
1425679200 Before You Buy
1425686400 Tech News 2Night
1425690000 Padre's Corner

Saturday, March 7

1425754800 The Tech Guy

Sunday, March 8

1425837600 The Tech Guy
1425852000 This Week in Tech

Monday, March 9

1425920400 Tech News Today
1425924000 Triangulation
1425929400 iPad Today
1425936600 Coding 101
1425942000 Tech News 2Night

Tuesday, March 10

1426006800 Tech News Today
1426010400 MacBreak Weekly
1426019400 Security Now
1426028400 Tech News 2Night
1426032000 All About Android

Wednesday, March 11

1426087800 FLOSS Weekly
1426093200 Tech News Today
1426096800 Windows Weekly
1426104000 This Week in Google
1426114800 Tech News 2Night
1426116600 Android App Arena
1426122000 Ham Nation

Thursday, March 12

1426179600 Tech News Today
1426183200 Know How...
1426188600 Marketing Mavericks
1426194000 Home Theater Geeks
1426201200 Tech News 2Night
1426203000 The Giz Wiz

Friday, March 13

1426266000 Tech News Today
1426269600 This Week in Law
1426280400 Before You Buy
1426287600 Tech News 2Night
1426291200 Padre's Corner

Most Recent Episodes

Security Now

SoHo router backdoors, web-based encryption service, evolution of DNS

Tech News 2Night

Shilling pitches back at trolls.

MacBreak Weekly

Apple Watch leaks.

Tech News Today

Updates from Mobile World Congress Day 2.

Coding 101

We finish our Arduino clock.

Tech News 2Night

Google Wireless is coming.

Triangulation

Becky Worley is the tech contributor for ABC.

TWiT Live Specials

Samsung Galaxy S6 Edge, HTC One M9, Acer Liquid Jade Z, and more.

Tech News Today

Mobile World Congress coverage.

iPad Today

Cord cutting options and other TV apps.

Know How... 103

NFC Tags, Differentials, and Assembling a Transmission

July 24 2014

Verizon goes symmetrical, what is NFC and how to make your own tags, different types of differentials, and assembling the LunchBox RC car transmission.

Verizon goes Symmetrical
If you're one of the lucky few who has Verizon FIOS, rejoice! You're getting Symmetrical!

What is NFC and Using Tags

NFC stands for "Near Field Communication" and, as the implies, it enables very short range communication between compatible devices.
* This means you'll need at least one device to send a signal, and another to receive the signal.
* NFC is a standard and can be used by a large number of devices, most commonly smart phones, but if you've ever used public transit pre-pay card they also work the same way.-"

NFC is based on RFID
* RFID stands for "Radio-frequency identification" which uses electromagnetic induction to transmit information.

* The most common use in smartphones is the peer-to-peer mode, which allows two NFC-enabled devices to send information, like a photo, webpage, or mp3.
* When in this mode both devices are active when sending data, and in a passive state when receiving."

Passive NFC devices
* Like this tag that i got from Amazon, can send information to other NFC devices without the need for a power source of their own.
* Also being passive means a tag doesn't process any information sent from other sources, and can't connect to other passive tags."

"* The biggest difference between NFC and other ways of sending information using radio waves like Bluetooth or WiFi, is that it can induce a electric current with passive devices as well as send data.
* The QI wireless charging that is based on the same principle"

Next there is the read/write mode
This is a one way data transmission, where the active device, like my smartphone, links up with another device to read information from it.

* For example you can program these tags to perform certain actions. I'm using a app called NFC Tools, if you want to get really nitty gritty you might want to try tasker.

Main benefits of NFC?

* The main one is much lower power consumption, NFC is perfect for passive devices, like these tags as they can operate without the need for a power source.
* Drawbacks are, the range is around just a few inches and NFC has a transfer speed of 424 kilobit per second."
* But NFC has fast connectivity. Without have having to manually pair devices, it takes less than one tenth of a second to establish a connection.
*So if you've ever seem Android Beam or S Beam on Samsung phones, they use NFC to quickly connect and then establish a Bluetooth or WiFi Direct connection to share information between devices.

TEFU: How to use NFC, demonstration video.

Amazon TagsForDroid - 12 NFC Pack

NFC Tools

NFC Tasks

Why do we need a differential?

Why do we need a differential?
Let's consider a real-wheel drive car:
* When the car is going straight, both wheels are rotating at the same rate
* HOWEVER, when the car is turning, the OUTSIDE wheel needs to rotate FASTER than the INSIDE wheel.
* If the two wheels were locked by a solid shaft, turning would be difficult because either the inside wheel would have to spin in place, or the outside wheel would have to slide to catch up with the vehicle.

That's what a differential does. It allows for differential rotation of each individual wheel
* In our video, you can see how a typical planetary gear differential works.
* The power is supplied to a gear that is tied to two smaller gears that engage gears attached to the drive shafts.
* Power can transferred to each shaft at different rates, allowing for the differential rotation speeds.

There are many different types and subtypes of differential, but we're going to look at three:

Open Differential:
* Inexpensive - Simple - Easy to Maintain
* Power is transmitted to the path of least resistance
-- However... because of this, if one wheel loses traction, all the power will go to the wheel that has lost traction.

Limited Slip Differential:
* In a LSD, SOME power will always transmitted to the wheel with the most traction
- This can be accomplished by using brakes on the wheel with the least traction
- You can use a hydraulic system
- You can use a clutch system

Locking Differential: Power is transmitted equally between all wheels.
* For use in rugged terrain when you expect to lose traction.
* It essentially removes the differential - allowing power to be equally distributed between the wheels
* HOWEVER, it also makes it very hard to turn.

Assembling the "Lunch Box" Transmission

* Lets figure out our Ratios

The Driver Ratio (aka "The Spur/Pinion Ratio")
* This is the ratio of teeth on the "Spur" the large gear inside the transmission that receives power from the motor, and the "Pinion" the gear attached to the shaft of the motor, which engages the pinion.

In our case, the stock Lunchbox motor and transmission use a 5:1 Spur Pinion ration
- 50 tooth Spur Gear
- 10 tooth Pinion Gear
** 5/1 gearing means that the spur gear will spin once for every 5 revolutions of the pinion gear.
** A Stock 540 power band is at about 20,000 revolutions a minute (It spins faster with more power, and a 540 maxes out at about 23,000rpm)
** At that power, the Spur gear will turn 4,000 time a minute

The Internal Gear Ratio (aka "Transmission Ratio)
* It's further reduced by the gearing between the Spur Gear and the Differential.

Connect with us!
Don't forget to check out our large library of projects at www.twit.tv/kh.
- Google+ Community at gplus.to/twitkh
- Tweet at us at @padresj, @Cranky_Hippo and @Anelf3
-Check out our transcripts.