Schedule

Schedule

Friday, October 24

1414180800 Android App Arena
1414191600 Tech News 2Night

Saturday, October 25

1414260000 The Tech Guy

Sunday, October 26

1414346400 The Tech Guy
1414360800 This Week in Tech

Monday, October 27

1414429200 Tech News Today
1414432800 Triangulation
1414438200 iPad Today
1414450800 Tech News 2Night

Tuesday, October 28

1414515600 Tech News Today
1414519200 MacBreak Weekly
1414526400 Security Now
1414533600 Before You Buy
1414537200 Tech News 2Night
1414540800 All About Android
1414549800 Padre's Corner

Wednesday, October 29

1414596600 FLOSS Weekly
1414602000 Tech News Today
1414605600 Windows Weekly
1414612800 This Week in Google
1414623600 Tech News 2Night
1414630800 Ham Nation

Thursday, October 30

1414688400 Tech News Today
1414692000 Know How...
1414695600 Marketing Mavericks
1414701000 Coding 101
1414704600 Home Theater Geeks
1414710000 Tech News 2Night
1414711800 The Giz Wiz

Friday, October 31

1414774800 Tech News Today
1414778400 This Week in Law
1414785600 Android App Arena
1414796400 Tech News 2Night

Saturday, November 1

1414864800 The Tech Guy

Sunday, November 2

1414954800 The Tech Guy
1414969200 This Week in Tech

Monday, November 3

1415037600 Tech News Today
1415041200 Triangulation

Most Recent Episodes

This Week in Computer Hardware

Civilization: Beyond Earth perfomance tests and building your own Dropbox.

Tech News Today

Facebook launches a new standalone app called Rooms that enables anonymous discussion.

The Giz Wiz

Pumpkin power saw, 3D scanner, and more.

Home Theater Geeks

Problems observed in Cinema Audio Systems.

Coding 101

Finishing the app building module.

Tech News 2Night

Etsy's new dongle, Aereo's legal future

Know How...

Hoverboards, Sticky Windows, and Quadcopter Pt. 2

Marketing Mavericks

Fan engagement with sports.

Tech News Today

Facebook alternative Ello raised $5.5 million in new venture funding.

Ham Nation

Gordon West explains why use a dipole.

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.

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