This is a follow-on from my first blog
NFC Uses
So why would I use it?. 
In the last post I discussed how NFC might be influencing our every day life.
But we can also make it useful to us as well.
I've been looking at a new car, and while I haven't been looking at the Dodge Hellcat (the Dodge Challenger SRT is enough).
I did notice they solved the issue of someone using all that performance when they don't need to.
They produced two keys types, one that supports the full ability (the RED key), and another that doesn't (the BLACK key).
The statement below says it all ..
The red key unleashes all 707 horsepower and every one of the Hellcat’s numerous performance settings for suspension, steering and traction control.
The black key limits peak power to “just” 500 while keeping engine rpm below 4000 and the transmission out of first gear (with no paddle shifter control).
This key should keep valets from destroying your rear tires while you eat, but even 500 horsepower and second gear would provide an entertaining joy ride…
source 2015 Dodge Challenger SRT Hellcat: Top 10 Amazing Facts about America's Most Powerful Car - Forbes
I'm presuming this uses the transponder chip in the key to change the ECU to reduce the engine performance, and transmission.
A long time ago there were two keys for cars.
One allowed opened the doors, boot, glovebox and access the ignition, while the other you handed to the valet and would only open the door and access the ignition.
While it allowed some protection for valuables it didn't limit the performance ...
I don't need that. 
Well that is one use, and I'm sure other manufacturers use the key tag to personalise some settings in the cars as well.
The tags within new car keys are an added expense (usually the dealer rips you off to program the car to accept it), but it does mean any copy of the key can't be used.
what else have you got.
I upgraded my smart phone (the display on the other was getting too small to see) and my new phone has NFC.
I thought how useful, I don't do Tap and Pay so its a waste. 
BUT the manufacturers included two stickers (tags) in with the phone.
One was a 'BED' tag, and the other a 'NAVIGATION' tag.
These are programmable, so you can modify what they control and then write it back to the tag.
So with some of these tags, I can stop having to access several menus to turn on and off the features I want.
It struck me that this could have been an alternative in my "Beyond the Phone" wireless challenge to detect if the tablet was still on its holder.
NFC Ring
Say what. 
This is a rather clever 'wearable' that incorporated two tags into a ring.
One is hidden while the other is visible.
https://www.kickstarter.com/projects/mclear/nfc-ring
The kickstarter was successful (806%), and I'm pleased to see John has been upgrading his unlocking app.
I was fortunate to win the Peoples Choice in the Beyond the Phone Challenge, and the prize was a Nexus 7 tablet.
This featured Wireless Charging and NFC.
At the same time element14 had procurred some customised NFC Rings, and Dr Christian DeFeo kindly found one for me.
They are based on the signature range and feature a Public and Private tag.
photo source http://store.nfcring.com/products/signature plus the 3 minions (me, myself and I)
Dudley Dudley has used one to unlock his phone, but the early version app has now been upgraded.
My Experience with the NFC Ring
I initially tried them on the Nexus 7, and it was difficult to find the right spot.
With the wireless charging coil also on the rear, the NFC 'sweet spot' was tricky to find using just the ring.
Now that I have a few tags, I will revisit it in a future blog.
I have been able to read (and accidently write) my ring using my phone, but it is a little tricky.
One of the benefits of the ring is that a simple skimming exercise tends to energise both tags, meaning the data is corrupted or invalid.
This also means unless you hold your mouth just right, your valid reader can also pick up both tags.
Can I make my own?. 
Becky Stern at Adafruit has done some very interesting things with tags.
https://learn.adafruit.com/unlock-android-with-wearable-nfc/nfc-tag-ring
photo source https://learn.adafruit.com/unlock-android-with-wearable-nfc/nfc-manicure
I'm quite sure that I won't be doing anything like that with my tags.
BUT it does give some interesting ideas for adapting the tags and integrating them into other products.
I'm still not convinced.
Last year I was asked if I could assist some year 7 students (11/12 year olds) in a project.
They were entering a "Neighbourhood Engineer" project sponsored by Transpower.
Neighbourhood Engineers Awards
The school had entered previously and made a scooter stand that allowed them to be locked, and not just laying everywhere.
They won that award and have continued selling the device around the country.
This year their theme was "Technology to assist the Elderly", and they decided they could use proximity tags to light up a LED on a key, so the elderly person knew which one to use.
The idea was great, but unfortunately the reality is different, so we adapted the design and made a portable reader.
The tag was fitted to the door, and pocket sized prototype held 4 keys with a LED next to each. When the reader detected the tag, it light the appropriate LED.
The reader was only one part of the project.
We identified that you couldn't mount a tag on a metal surface, and the cards had no markings to allow them to be fitted.
The solution was a 3D printed enclosure, that raised it from the surface, and provided mounting options.
Sadly I don't have photos of the final reader prototype.
http://www.nea.org.nz/2014-Winners.cfm#JM1
It should be noted that these weren't the only parts of this entry.
They included identifying wireless charging devices to fit their grandparents electronic devices, the shopping bag holder and a 3D printed universal fit piece to assist turning a key.
Tags
They are all the same right?.
Unfortunately they aren't all the same.
Besides the tag electronics, there are different frequencies.
The common one is 125KHz, and you can find tags, and cards for these from many sources.
They come in different shapes, colours and tend to be a certain size.
Micro-chips for implanting into animals tend to be 134KHz
I have also seen similar tags in 125KHz but these are NOT designed to be implanted.
Most 'prox' tags are 13.5MHz. The range is improved and the tag antenna can be physically smaller.
Likewise some of the readers can only read certain tags and some can read and write to certain tags.
So if you decide to go and buy a reader and tags, please ensure they are compatible.
Okay enough talk show me.
In the next blog, I'll show an example using an Arduino, and the Raspberry Pi EXPLORE-NFC.
Mark
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