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This is a nice write-up on interfacing analog meters via USB. The project is fairly complicated, and you have to have good soldering skills to make it all work. Don’t forget, an Arduino can do this kind of thing, and it might be a little easier too!

In a sort of retro mash-up, we’ll make a USB device that displays PC status info on these gauges. The gauges can show CPU and memory usage, processor voltage — just about any numerical data typically displayed on small HD44780 based LCD character displays commonly used in PC case mods.

Driving an analog gauge – [via] Link

Related:
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Homemade analog gauge controller for PCs – Link