Switches are an interface between machines and us. We can control them by switching ON/OFF as per the requirement. Now we can broadly divide these switches based on means of controllability into mechanically and electrically controlled. A switch present in the switchboards in our homes can be categorised into mechanically controlled as we switch between ON-OFF using our hands/ by other means. We can control these switches by ourselves as long as the switching rate is within the human capabilities. Many of the applications at micro-level(in microprocessors), macro-level(in the regulation of heavy machines) or in unfeasible environments can be accomplished by the electrical control of switches. Now in layman’s terms, consider that power board switch. Observe that it has 2 terminals, and the control is using our hand/by other means. For an electrical switch we need to replace the control by hand with a wire(since electrical is all about wires :) ). So an electrical switch has an extra terminal, and we have a 3 terminal device that switches between two states.
So in this module, we will learn about 2 such switches: MOSFET as a switch and a relay. Both of these are 3 terminal devices. The 2 terminals are the usual circuit connections, and the 3rd terminal is the control terminal. Now, this control is given by a microcontroller(say an Arduino UNO). The switch between states depending upon the voltage on the control signal. If this voltage is lesser than a certain threshold, the switch will be OFF and vice-versa.
Now use a 1)Relay(LU-5-R) 2)MOSFET in your circuit and make an electrically controlled switch. In your circuit use an LED, a resistor, a battery and one of these switches. Connect all of them in series and check if the LED switches ON/OFF as directed by your instructions through micro-controller. Enjoy switching!