I am working on a concept for a programming tool for primary aged students. The purpose of this post is to ensure I haven’t missed an obvious solution to the following problem:
The tool requires an array of sensors, which can be read sequentially, each senses the angular positions of a token (with a resolution of 8 possible positions for each sensor). The token will be constrained in its position, like a star shaped puzzle piece, with 8 positions possible.
It needs to be cheap (<$1ea), contactless, and reliable for the tool to be viable. There would be around 20 sensors.
(edit>) Each token would be around 40mm in diameter. (<edit)
Using an Arduino is also a requirement.
Currently I plan to use an LDR and LED pair. The token would be placed over a recess (shielding it from external light) an 1/8th segment would be open to the LDR, illuminated by the LED.
(edit>) The LDR would ‘read’ a shade, from black to white in 8 steps, from the exposed segment of the token. (<edit)
This would then be read in an analog matrix fashion.
From a few tests this seams viable. Alternatives I have considered include:
- PixyCam (CMUcam5)
- Hall Effect Sensors
- 8 x Reed Switchs for each token
All of which seem either too expensive or more difficult to construct and implement.
The PixyCam would be the ideal solution, as it is future proof for the application. However, it is also 4 or 5 times the price of the LED & LDR array. The fast frame processing rate of the PixyCam is not required, a cheaper static or low frame rate version would work if one existed, the PixyCam interface would be nice though.
In closing, how would you tackle this problem? What is the best method? Have I missed something?
Thanks in advance,