RFID Reading Field Visualizing Probe Design

Introduction

Last week while I was watching some videos on Vimeo looking for inspiring material, I hit the jackpot: “Immaterials: the ghost in the field”. I was so intrigued by their work; I didn’t even pay attention to the publishing date (2 years ago). While watching the video ideas started rushing through my head, since for a while I’ve been working with RFID and always faced problems with the reading field of the antennas. Of course going to the datasheets and trying to figure out the reading volume’s shape could be one possibility, but it’s just not “real” enough. I wanted to know more about the people behind this project and reached nearfield.org. The research was complete, the papers were published, the website was last updated in 2011 but people were still posting comments.

I started wondering what happened to this amazing technique, and why no one has pursued this study. In the meantime, while I could not argue the beauty of the outcome of this technique I couldn’t resist not thinking of how inefficient, time consuming and limited it was. So I decided to design my own tool that could take this research a step further.

RFID Reading Volume 3D Mapping Probe:

The concept is simple; it is visualized in the diagram below:

RFID Reading Field Visualizing Probe High level architecture
RFID Reading Field Visualizing Probe High level architecture

 

 

The diagram is at a very high level of abstraction and it’s not worth going into its details at the moment as some components might vary upon implementation. However, I’m gonna describe what is illustrated above:

  1. The Probe is made out of 5 modules:
    1. RFID Tag
    2. Coordinates Recording module
    3. Accelerometer
    4. LED
    5. Controller
  1. Once the Probe, specifically the Tag (1a) is at a reading distance from the RFID antenna, the reader dispatches a signal to the processing software layer that will in turn trigger the recording algorithm.
  2. The recording algorithm will ask the Controller to grab data from the 2 modules (1b and 1c) and will ask the LED (1d) to blink.
  3. The data is then gather, analyzed, stored and the coordinates with the accelerometer data will be used to draw 3D point cloud of the reading volume.
It is worth to note, that this Probe can be adapted to different technologies. Actually, any technology that offers instance response.

To be more specific, I drew a simple annotated sketch of how the probe might look like:

RFID Reading Field Visualizing Probe Sketch
RFID Reading Field Visualizing Probe Sketch

This design is currently pending a prototype. I’m gonna be working on it as of next week. I’ll update this post accordingly.

I will choose one of these 2 paths:

  1. Develop a mobile application and embed the missing modules to a smart phone and have the application do all the logic.
  2. Implement the probe using an open source controller (Arduino and the likes). I’m sure I will not need much processing power on the Probe level since all the work will be done by the controlling pc.

Potential Value:

Since this is a side project, I will neglect all business value of this project and focus on the personal educational benefit; maybe some student, researcher might find value in this work as well. I have not yet done my homework with regard to looking for off the shelf solutions; I am going to work on it either way, even if some argue that I’ll be re-inventing the wheel.

 

 

Sparkfun: Color LCD Shield back-light problem patch

Problem

As I was working on a project that makes use of the Sparkfun color LCD shield I noticed after running sample code that the back-light is not working properly. Adding to that, it was a bit challenging to find Arduino (v1.0) compatible libraries to make this shield work as it was intended. The solutions for these 2 problems are summarized below.

Back-light fix

Credit is due where credit is due. The original hacker who, with a bit of research and reading a few comments on the product’s page, found the solution can be reached through this link. Although the description of the fix is quite straight forward, I though it could be simplified more.

The problem relies in a resistor on the board (R1) that was supposed to have the value of 15KOhm but was (for some reason) replaced with a 3.3KOhm resistor (as shown in the picture below).

Original Color LCD Shield - sku: LCD-09363
Original Color LCD Shield
sku: LCD-09363
images are CC BY-NC-SA 3.0

 

 

 

 

 

 

 

 

 

 

 

In order to resolve this issue and provide enough voltage to activate the back-light, this resistor needs to be short-circuited by soldering the edges of 2 components as shown in the picture below. A small solder drop is enough to provide you with an elegant fix.

 

 

Soldering fix
Solder the 2 edges and you’ll be good to go.
Close up for the fix
Close up for the fix

That should do it.

Libraries compatibility problems

I naively assumed that upgrading my Arduino IDE to version 1.0 would not break any existing library, however as it turns out it does. The libraries that enable the color LCD shield do not work with v1.0. The libraries that are available either use “WProgram.h” or “wiring.h” header files which have been merged in the new version of the Arduino IDE with the “Arduino.h” header file. In addition, replacing these header files with “Arduino.h” does not seem to fix the compilation error.

So in order to avoid hours of pain, Arduio IDE v0023 runs the LCD shield libraries perfectly well.