In all kinds of engineering, we build on abstractions in a kind of inverted pyramid. Lots of people can, for example, design a system using ready-made building blocks on printed circuit boards. Fewer ...

Here is a simple mod to allow the speed of any 12V fan to be varied. All we need to do is insert a rheostat or variable resistor in the 12V wire to the fan. The rheostat should be rated at least 3 ...

In a recent thread I helped perpetuate the myth that rheostat power rating should be 1/4 the fan wattage. Checking some datasheets gave a more accurate formula.<P>Manufacturers such as Vishay quote a ...