Ben Krasnow found a method to control speed of a universal motor (a 120V AC drill motor in this case) by using a CdS photoresistor instead of the original variable resistor used to control the standard triac dimmer circuit that was the drills trigger. The CdS photoresistor is driven by an LED that is controlled by a PWM pin from an arduino microcontroller. This system provides a very easy way to control 120V AC devices with a single PWM pin, and not use any timing code or worry about zero-crossing of the AC power since this is done intrinsically in the circuit. It also offers true electrical isolation between the AC line voltage and microcontroller.
Simplicity at its best.
Forrest Higgs wanted a way to measure distance for a robot he is making without the need of ultrasonic rangefinders, only alternative he had was with laser for direct measurement or offset trigonometric measurement.
Since direct measurement lasers cost alot he went with the second option, he placed a web cam and a laser pointer point...
CNCroro made a made a CNC foam cutter from easy to find and cheap materials. The low price of the project doesn't mean low results though, the accuracy provided by the four unipolar drivers is up to 0.006mm/step making it more than adequate for a good precision project that its builder desired.
Cutting at spee...
Luk made an inductance meter which comes in handy when winding your own coils or transformers as needed in switching power supplies. It becomes even necessary for winding flyback transformers where the air gap must be adjusted.
The author of the original circuit is unknow but Luk made the PCB and added an additional range switch and a buzzer.
Complete details and schematics can be found here.