Electronic – How does a Capacitive ID / Signatures / Sensing system work? e.g. Google Bloks

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In the 'Google Bloks' project. A tangible programming experience is created by allowing children to place physical instruction blocks 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).

  • Each instruction card contains no electronics.
  • Each instruction card is somehow assigned a 'capacitive signature'
  • Instruction cards are decoded via some capacitive sensor matrix

Since there is no technical whitepaper. My question is how would this work in practice?

  • How to design the sensing system for this?
  • How would you create a capacitive signature for an instruction card?

Best Answer

So basically what I though.

The baseboard has a cap sense pattern of 8 pads, and a center magnetic sensor (hall effect?). With 8 pads, the "capacitive signature" will be as simple as conductive paint at any binary representation of 8 bits. Boom, 255 pucks. The magnetic sensor is used for "complex" pucks.

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From the technology page of the project's website:

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.

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