Potentiometer
Till now, we’ve learned what analog signals are – their nature, and how to identify them; but we didn’t dig enough (yet) to find out how one can vary the signal so smoothly, which, in our case, is voltage. For that, let’s have a look at the cute little knob on your music system that helps you listen to the songs of your favorite heavy metal band at its loudest, a.k.a. the volume knob.
The volume knob lets you turn up the volume when you’re alone, and quickly turn it down as soon your parents enter the house. But did you ever wonder how your saviour actually saves the day for you, (almost) every. Single. Time?
The volume knob is a small but an extremely important device known as the potentiometer.
A potentiometer is nothing but a variable resistor, i.e. we can easily vary/change the value of the resistor by moving or turning the slider or the knob. Since the movement of the slider or the knob is smooth and continuous, the change in the value of the resistance is smooth. Also, we know from the previous lesson that whenever there is a resistor in a circuit, a voltage drop takes place across it, and this drop depends on its resistance. Therefore, as the resistance changes, the voltage drop also changes; this change is smooth since the change in resistance is smooth. This change is the voltage drop allows us to control the volume. How voltage gets converted into the volume is a different story for a different day.
Other than controlling the blare of the heavy metal songs, potentiometers are also used to control other things such as the brightness of lights…
…which brings us to the end of this topic and the beginning of the next.
Controlling the Brightness of LED
Coming up: an activity to build a circuit that allows us to change the brightness of an LED.
In this activity, we’re going to make a circuit that will allow us to change the brightness of an LED using the potentiometer knob that we have on evive. In fact, we have two of them. The two knobs to the right of the screen labeled as 1 and 2 are evive’s potentiometer knobs.
You can use knob 1 in your circuit via pin A9 and knob 2 via pin A10. Both the pins are under the magic lid towards the top left corner. For this activity, we’ll use knob 1. Take out your starter kit, put on your working caps and let’s get started!
What you’ll need:
- An LED
- 2 male-to-male jumper wires
- A 220Ω resistor
- The powerhouse: evive
What you must do:
- First, take one of the jumper wires and connect it to pin A9. Insert the other end the 1st hole from the left in the first row of the breadboard.
- Next, take the 220Ω ohm resistor and insert one of its legs in the same column as that of the jumper wire, but in the row below it. Then, take the other leg and insert it 1st hole of the second last row of the breadboard.
- Now, take the LED and insert the positive terminal in the same column as that of the resistor, but in the last row. Next, insert the negative terminal in the 5th hole, from the left in the same row, i.e. the last one.
- Finally, take the second jumper wire and insert one of its ends in the same column as that of the negative terminal of the LED, i.e. the 5th from the left, in the second last row. Take the free end and connect it to the GND pin of evive. It is presently under the magic lid in the top left corner, where there is a stack of 6 pins, 3 in the top row and 3 in the bottom; the GND pin in the bottom row.
- Once all the connections are made, switch evive ON by sliding the switch to INT. Rotate the potentiometer knob and observe how the brightness of the LED changes smoothly.
Below is the complete circuit:
