Ralf Kelz

The exposure tester in this Design Idea measures the on time of a light source, whether an LED, an incandescent lamp, a halogen lamp, or another source. It can be made with an ordinary stopwatch and a few simple components (figures 1 and 2). An electronic stopwatch...

The circuit in this Design Idea bootstraps a large capacitor in series with the solenoid to provide a large actuation voltage (Figure 1). This higher voltage provides substantially more current to operate the solenoid, speeding the operation of the solenoid. You can also...