Basic Electronics

Multivibrator circuit is one of the first projects you start learning electronics. It is really wonderful circuit widely used for educational purposes and even in end projects as waveform generators. Lots of hobbyists simply grab a microcontroller/Arduino to blink LEDs. But using basic circuits like multivibrator may be cheaper, faster and even fun. [Ray] decided to go through multivibrator theory and explain its working in detail step by step.

Circuit itself consists of two transistors, two capacitors and four resistors. When powered, circuit generates square wave signal that can be used to flash LEDs, or clock other circuits. You will get an intuition on what causes multivibrator continuously generate. Formulas allow to calculate resistor and capacitor values for particular frequency. Especially if you are starter in electronics build one on a breadboard and do some experiments, why not to start wit Christmas lights.

This tutorial is more for digital guys who usually control things with microcontrollers and other digital circuits. Simple motors, relays, LEDs cannot be connected directly to microcontroller pins because they require more current that I/O can provide and in other hand this isn't safe way to do so. Take a look at this great video tutorial how to use simplest pnp transistor properly when controlling electromagnetic air-valve.

Probably you've done tons of similar circuits with same relays. What you usually do is connect about 1kohm resistor in transistor base circuit ant things work just great. But if you want to understand how actually transistor currents depend on each other and how to select proper transistor and right base current limiting resistor spend some time and make things clear. Completing this you will be able to build more safer and energy efficient circuits. [via]

Most of you here have heard Pulse Width Modulation (PWM) at least once in your life, but how well do you know about this PWM? If you want to unveil the mystery of PWM, then you need to spend a few minutes to read on this article...