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ElecFreaks' Dot-Matrix Light-Pen Project

Gareth Halfacree

Chinese companies often get a bad rep in open hardware circles, largely thanks to the undeniable product cloning that runs rampant in the region. Not all companies should be tarred with the same brush, however, and ElecFreaks is definitely one of the good guys. This is demonstrated admirably by the company's latest clever creation: a light-pen input device coupled with an LED matrix display to create a low-resolution notepad.

In the current market where capacitive touch screens, resistive touch screens, TFT displays are flooding [the market], DIY enthusiasts have rarely used dot matrix screens. Here we use a 5mm 8 * 8 dot matrix screen and phototransistor to achieve a pen write function. Sounds fun? But how to specifically make it? Can we achieve a larger area pen write?
The project is mainly composed of three parts: row scan circuit, column scan circuit, the pen’s circuit. It has a photosensitive sensor in the pen, we use this pen to get the states of [the] LED.
ElecFreaks' project can be viewed in full, complete with schematics and source code, over on the official website. The team did encounter some problems during the build, including issues with sensor noise, and ask for input on improving the design.

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