Schedule

Schedule

Monday, October 20

1413824400 Tech News Today
1413828000 Triangulation
1413833400 iPad Today
1413846000 Tech News 2Night

Tuesday, October 21

1413910800 Tech News Today
1413914400 MacBreak Weekly
1413921600 Security Now
1413928800 Before You Buy
1413932400 Tech News 2Night
1413936000 All About Android
1413945000 Padre's Corner

Wednesday, October 22

1413991800 FLOSS Weekly
1413997200 Tech News Today
1414000800 Windows Weekly
1414008000 This Week in Google
1414018800 Tech News 2Night
1414026000 Ham Nation

Thursday, October 23

1414083600 Tech News Today
1414087200 Know How...
1414090800 Marketing Mavericks
1414096200 Coding 101
1414099800 Home Theater Geeks
1414105200 Tech News 2Night
1414107000 The Giz Wiz

Friday, October 24

1414170000 Tech News Today
1414173600 This Week in Law
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

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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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