A previous Design Idea describes a circuit that uses an astable multivibrator to drive an LED (Reference 1). The circuit in Figure 1 uses a simpler alternative approach. The circuit uses a 2N3904 NPN ...

Photocouplers optically links, via transparent isolating material, a light emitter and a photodetector. Used as an interface between circuits with different ground potentials, photocouplers replace ...

A very simple but highly efficient combination lock circuit is shown in the figure. Any type of on/off switches can be used, varying from commercially available inexpensive types to more sophisticated ...

The Joule Thief Circuit is a simple and clever electronic design that can power an LED using a nearly dead battery. The project demonstrates how basic components like a transistor, a toroidal coil, ...

In this lesson, students build two circuits and explore how transistors function. When Bell Labs introduced the transistor in June of 1948, a spokesman proudly announced "This cylindrical object . . .

This project is a basic flip-flop (astable multivibrator) circuit that alternately blinks two LEDs using two NPN transistors, capacitors, and resistors. The circuit uses capacitor charging/discharging ...