Andrew Morris had a problem with a small rotary tool built in China. The tool fit nicely in the hand and was useful for precision cutting, drilling, and polishing. Yet for delicate work, the tool was in bad need of a speed regulator.
Andrew had developed an analog motor speed regulator back in the mid-1990s, but this time, he wanted the benefits of a digital regulator. The digital version was just as efficient, but it was less expensive to build and easier to assemble. The digital circuit also provided more torque.
Andrew Morris' microcontroller-based DC motor speed regulator brings control for delicate work.
This gadget turns something that's almost useless into something that any gadget maker should find useful. The AC-powered rotary tools are great for heavy work, but this gadget is exactly what is needed for delicate work. The tool fits very nicely in the hand, giving the user excellent control of the drill bit, cutter or polisher. This is critical when replacing tiny surface-mount parts on printed circuit boards (i.e. cutting away old parts), where uncontrolled speed or poor manual control could tear the part off the board, causing damage. In addition to that and many other things, I've also used my older mini-drill and analog speed regulator to polish away oxidation from the tiny switch contacts in my wireless computer mouse. High speed would have torn the delicate contacts right off the tiny switches. With this gadget, the mini-drill has enough torque for most not-so-delicate work as well.
Since this article was written, the digital speed regulator has worked so well for so many projects, that the analog unit doesn't get used anymore. I keep it around since it has a lower minimum speed than the digital unit, just in case. Getting stable performance from the digital circuit at extremely low speeds might be a challenge. I haven't tried it, since the current minimum speed of the digital control has so far been perfect for my needs.
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