Les signaux : Signal numérique

What is Digital Signal?

A digital signal is a signal that represents a quantity as a series of discontinuous values. It isn’t analogous to the original quantity/quantity that it is representing. It can only represent a set of discontinuous values; the number of these values ranges from 2 to any number that is not infinity. The simplest digital signal can represent only 2 values: ‘zero’ and ‘one’, or ‘true’ and ‘false’, or ‘HIGH’ and ‘LOW’, and it is known as a binary signal.

We’re surrounded by digital signals. Devices such as laptops, computers, mobile phones, televisions work on digital signals. In fact, laptops, computers, and mobiles don’t understand anything other than the digital language.

If we were to represent a binary signal using a voltage vs. time graph, it would look a square wave, like the one below:

Sometimes, digital signals are also using to represent analog signals in discrete/discontinuous steps. When we visualize these signals from a far place, they seem to be continuous; but when we look at them in detail, we realize that they are small, discontinuous steps.

Activity

Let’s make a simple circuit to see what a digital signal looks like.

What you’ll need:

• a 10kΩ resistor
  
• 2 male-to-male jumper wires
  
• 2 male-to-female jumper wires
  
• a tactile switch
  

What you must do:

1. First of all, take the tactile switch and insert it across the gap in the breadboard such that each leg goes in a different column.
2. Next, take the 10kΩ resistor and insert on of its legs in the same column as that of the left leg of the tactile switch, and the other in any other column on its left. Make sure that you leave a hole empty between the left leg of the switch and the resistor leg.
3. Now, take a male-to-male jumper wire, and insert one of its end in the same column in which the left leg of the resistor is inserted. Then, connect the other end to the GND pin in the analog pin stack labelled as ANALOG IN, right above the breadboard. There will be two GND pin; connect the wire to the first GND pin.
4. Take the second male-to-male jumper wire and connect one of its ends to the 5V pin in the ANALOG IN pin stack. Take the free end and insert it in the same column as that of the right leg of the tactile switch. Once all of this is done, it’s time to bring in the graph pins.
5. Take a male-to-female wire and insert the male end into the hole between the left leg of the switch and the resistor. Then, connect the female end to the left GRAPH pin. Next, take the second male-to-female jumper wire and connect the male end to the second GND pin the ANALOG IN pin stack. Then, connect the female end to the GRAPH pin in the middle.

And you’re done! Turn evive ON by sliding the switch to INT, and select Mini Oscilloscope; you’ll see a green line in the centre of the screen. Whenever you press the switch, you’ll see a rectangular pulse that stays there for as long as you press the switch; and more the number of times you press the switch, more will be the number of pulses.