This is a follow up question to 'How does a Capacitive ID / Signatures / Sensing system work? e.g. Google Bloks'
In the 'Google Bloks' project. A tangible programming experience is created by allowing children to place physical instruction blocks (Pucks) next to each other.
The computer is able to read the sequence of instructions and turn it into a program to e.g. control a robot.
It uses a capacitive sensing / capacitive ID system to detect whether an instruction card is a "GO FORWARD" or a "TURN LEFT" card (for example).
From the technical whitepaper :
Pucks are easy to create, for example by cutting paper, or 3D printing the form and then drawing the capacitive signature with conductive ink. This enables an infinite number of commands to be easily made on the fly by anyone.
The Base Boards have their function specified by the puck placed on them. The Base Board has a capacitive sensor and magnetometer. The capacitive sensor reads the command expressed by the puck, and the magnetometer detects the state of the mechanical control by reading the magnet position.
The Base boards are able to read the capacitive signature of a puck to identify it:
I am interested in how Google Bloks uses capacitive sensing to read the conductive paint pattern, and decode it as a Puck identifier.
Looking at the images more closely, we can see the materials used for the pucks - one layer (A) with a conductive pad and the other (B) an insulator.
My guess is that if one were to paint the insulating layer (B) with some conductive ink, then together with layer A, the puck will form a capacitor. The value of its capacitance will vary depending on the pattern drawn. Thus the idea of a capacitive signature that can identify a puck.
My questions are:
Would this work in practice? Could the capacitance value be reliably read, to uniquely identify a puck?
How to detect the capacitance, contactless ? The pucks have no electrical contact with the 'reader' base board.