Photo 2 looks more like a triangle wave than a sine wave. It is certainly not a very good sine wave. A filtered square wave from Figure 1, output A.

Photo 1 is the result of two stages of filtering (note different amplitude scale). Photos 1, 2, and 3 show the result of filtering a square wave at outputs A, B, and C, respectively. The component values will vary according to the desired frequency. However, a reasonable sine wave can be created with a three-stage RC (resistor-capacitor) filter that is shown in Figure 1.įIGURE 1. This is easier said than done because simple passive filters are not too efficient. If the harmonics can be removed, then a sine wave of the fundamental frequency remains. Basically, a square wave consists of a fundamental frequency with a lot of higher harmonics. The simplest method of converting a square wave to a sine wave is by filtering. The goal of this article is to familiarize the reader with a number of different techniques rather than to describe those techniques in detail. This article will briefly examine a number of methods of creating sine waves, and other waves, from digital values. And while they can do this quickly and efficiently, there are many more types of signals in the real world that require something other than zeros and ones. To make it less of a hassle, we can insert a toggle switch in the circuit so that we can just toggle the lever of the toggle switch if we want to turn ON or OFF the light bulb, instead of connecting or disconnecting the electrical plug.Most digital circuits are limited to outputting zeros and ones. So to turn ON the light bulb, we’ll insert the electrical plug to the outlet and to turn it off, we’ll disconnect the plug from the outlet. I hope you can imagine it, in reality, the light bulb is connected to the AC mains or wall outlet through an electrical plug and zip-cord.

In figure 3, we can see a schematic diagram of a light bulb connected directly to the AC mains. So basically, an SPST toggle switch is simply an ON-OFF switch with two terminals (A & B) that can be connected together or disconnected from each other by toggling the lever (actuator). An SPST switch has one pole and one throw, so it can only control one circuit and its pole can be connected to one terminal only. The number of poles in a switch determines how many separate circuits the switch can control while the throw-count of a switch tells us how many positions each of the switch’s poles can be connected to.

In figure 2, you can see a single-pole, single-throw (SPST) toggle switch and the circuit symbol of an SPST switch. A switch is an electrical or electronic device that can open or close a circuit, stopping or allowing the flow of current in a circuit.

Bipolar square wave equation