Hello everyone. I welcome you to my blog post describing (not only) my Custom NFC Tags which I designed, ordered and assembled as part of NFC or RFID Project14 Competition.
I originally promised different project in the discussion of the main competition thread. In the meantime, I got better idea. I originally promised wheel of luck with NFC tag and reader for indicating wheel location. This looked to me like a cool toy but otherwise it was quite useless. But in meantime I got better (and more useful) idea. I decided to upgrade my Duratool Storage Box again. Now with NFC tags. Last time it was successful, so I try to continue the success of this storage box which I originally received for free from Element14. My original idea was to make offline search tool. Every cabinet will have tag with ID and 2D coordinates of cabinet location (row and column in the storage box). Except this information tag will remember parts inside the cabinet and also some parts in nearby cabinets (and their locations). Because capacity of tags memory is limited it will know only about locations of some of the other parts, not about all. Then you will be able to use reader, enter name of part and search it in two steps. The first step is find any cabinet which know location of the thing. As I mentioned cabinets do not know location of all parts, so it may take multiple attempts. After you find any cabinet which know it, it switches to the navigation mode and using X and Y location of tags will show arrow on display navigating you to the correct cabinet location. Because all tags know the X, Y locations it is possible to update row when moving reader near cabinet and seamlessly navigate you to the destination which contains searched thing.
Did not receive NFC Reader
The issue is that I did not received NFC reader (in time). I ordered ST X-NUCLEO-NFC03A1 as part of my reward from previous Project14 competition. Because of some delays in ordering my basket it went out of stock and was backordered but even it was restocked about month ago I still did not receive it. Time run out, and I had to redesign my project for being able to complete it even without NFC reader. For this reason, I was thinking about NFC readers, and I realized that almost every phone has NFC reader, so I tried to proceed in this way. Unluckily NFC in iPhone is very limited and software support in iOS is also very minimalistic. Every interaction requires to pop up system window and all actions must be executed by user interaction (pressing button), so it is hard/impossible to make app as interactive as I originally want. For example navigation to target cabinet mentioned in previous section is impossible to implement without requiring user to click button after moving hand by every ~7 cm.
Alternate Project Idea
I let original idea in the background but simplified it for being able to realize it with iPhone NFC reader only. I added tags to every cabinets and programmed tags with information describing content of the cabinet. After placing phone near to the cabinet, you can find its content even without opening the cabinet. Sometimes it is useful. For example, when you have multiple resistors/capacitors/inductors or other small components in the multiple cabinets, and you do not know if it is in first or second cabinet with the passives. Searching with phone may be faster than looking on every component in the cabinet and checking its value before realizing that searched part is in different cabinet… I implemented it and I find it very useful in this situation.
See it in the action!
These tags I used as part of my project, and you will see them later.
Experiments was also sponsored by ST. ST send me free samples of ST25DV64KC-IE6T3, ST25TN01K-AFH5 NFC Tags. I ordered them in the time when shipping on their store was free, so I received them totally for free.
Finding Location of Phone NFC Antenna
But before I started developing my project, I tested very interesting Field Indicator card from tag bag and checked where do the iPhone has NFC antenna? As you can see on the video below it is in upper part of phone.
Custom NFC Tags
For my project I need 30 tags because storage box contains 30 cabinets. In fact, I need less because I do not need to tag cabinets used as temporary storage or cabinets containing only one easily determinable part. I decided to tag 20 of 30 cabinets. Tag bag do not contain required number of tags and some of them are too large for cabinets, or they have very specific use case (like tag that you have seen for indicating NFC field strength). For this reason, I designed my own PCBs with trace antenna and made my own NFC tags!
This was my first design with any antenna. Because I am not skilled in RF, I was not sure if my design will work. For this reason, I tried three different designs. All I ordered on OSHpark and assembled them.
Here they are: