We are going to go over wiring up circuits on breadboards and use this as an opportunity to wire up the circuits that we'll be using for the rest of the chapter. If you are already a pro in breadboarding and circuitry, feel free to move on to the next video.

Breadboards are the bread and butter of prototyping as they allow you to wire up a circuit quickly and temporarily without any soldering at all. Here I have two common sizes of breadboards. We will be using the larger one because it's a bit easier to fit all of our components onto it, but all breadboards typically work the same, regardless of size or brand.

So we have all of these holes or contact points here, which is what we will be placing our components and jumper wires into. And these are actually connected together in a series of rows and columns. All the points on these two outer sections are connected in long rails here, often called the power rails. And all of these inner holes here are connected in rows of five. So in row one here, pins A, B, C, D, and E are all connected together and so on for every single row.

Here I have a voltmeter wired up so that if I make an electrical connection with these two jumper wires, we read 3.3 volts. So if I plugged one into this row here, you can see that four of the other points in this row are also electrically connected together, but not the ones next to it or the ones across the board on the other side. If I plug one into these outer rows here, we can see that every single pin in this negative rail is connected together. And same deal for the positive one. And something that catches a lot of beginners off guard is these two outer rows are not connected together. So if I've got one plugged into here, none of these rows will make an electrical connection.

Now something to keep in mind is that there is a limit to the amount of current that you can run through these connections on the breadboard. About one amp is a safe limit, and we will be talking about this in a later video. But for everything that we're doing in this chapter, we aren't going to encounter any issues with that just quite yet.

Now we're going to wire up some circuits, starting with the circuit from last video, just that LED and resistor combo. Remember, as always, we should ensure that our Pico is unplugged and unpowered before we start wiring up anything to it. A good first move is to place the Pico into the breadboard like so, just on the centre edge here with the USB sticking out on this side.

We're going to start by connecting the power rails of the breadboard to the power output pins of our Pico. We'll start by connecting any of the ground pins to the breadboard's negative rail. I'll just be using the top one here because it's easy to find. And then we'll connect the 3V3 out pin of the Pico to the positive power rail on the breadboard.

Now this 3.3 volt output pin we have just connected will always supply this voltage when the Pico is plugged in. It's not like a GPIO pin where we have to tell it to do so with code. It always supplies that voltage. And this is really helpful as it kind of acts as a battery or a power source which we can use to power the things that we're about to plug into our Pico.

Now we're just going to plug in our LED and resistor according to the diagram. This resistor is called a current limiting resistor and without it you will kill the LED. It can't just be any random resistance value but picking that exact value is a bit too advanced for this video right now. So if you have a packet of LEDs that came with resistors, use the resistors from that pack. If not for these normal LEDs a resistor between 220 and 500 ohms will work very nicely. We will then connect one side of the LED and the resistor to ground with a jumper wire. Just like so. Now the LED does have a polarity meaning that it will only work one way. If you look closely one of the legs will be shorter than the other. We call this one the cathode and it should be the side that is connected to ground. Don't worry too much about getting it the right way around. You're not going to kill the LED by putting it in the wrong way. You can just flip it around if it doesn't work.

And we will finish this off by connecting the other side of the LED and resistor to pin 16 of our Pico. If you wanted to you could now run the code from last video as we talked about. Just ensure that you have changed the code to use pin 16 instead of the onboard LED. And as always double-check that your circuit is correct before you plug in or power on the Pico.

Right now I've got that code running here and this is a good opportunity to introduce the concept of a closed circuit. Now a closed circuit just means that you create a nice loop for electricity to flow in but it's vitally important as without it nothing here is going to work.

We are also finally going to introduce voltage and current which are often a bit tricky to understand at first but a very common analogy to use is water. Now imagine this circuit is a sort of water system instead of an electrical system. Our Pico starts from ground or zero volts and outputs 3.3 volts on pin 16. And you can think of voltage as kind of like water pressure. More voltage is more pressure so it goes from no pressure at ground to 3.3 volts of electrical pressure at pin 16. And you can also think of the Pico as having a tap on that pin which we can turn on and off with code to control the pressure on pin 16. And as it passes through them it loses its water pressure or voltage as it goes back to zero volts or no pressure at ground. And the flow of water in this analogy is current. The more current the faster the flow of electricity through the circuit.

Now when we unplug this wire here we create something called an open circuit and the LED isn't turning on anymore because electricity doesn't have anywhere to flow. We no longer have a nice closed circuit. Think of this wire here as a pipe that we have blocked off on the end. Water's got nowhere to flow. You can have a lot of pressure coming from the Pico, a lot of voltage, but if there's nowhere for the water to go there's going to be no water flow through the circuit. There's going to be no current flowing through the circuit and so nothing works. There's no power delivered to anything. But when we plug it back into ground we make a nice closed circuit again and electricity can flow in a loop. And this is a very important concept when making circuits with components like these as a loose connection or a wire in the wrong place can stop that flow of electricity and nothing is going to work.

Now we're going to use the rest of this video as an opportunity to wire up two more things on our breadboard which we will be using in the coming videos. We will continue by placing the button in the middle of the breadboard like so and connecting one side of it, I'm just going to select this pin here, to the power rail of our breadboard. And then we'll connect the other side of it, I'm just going to select this one here, to GPIO 15 of the Pico.

Now we're going to connect a rotary potentiometer to our board which has three pins on the bottom. So we're going to plug that into the breadboard and we're going to make sure that each pin sits in its own row and they're not connected together. We'll plug the other two pins of our potentiometer into ground and our 3.3 volt rail. It doesn't really matter which side is which, it'll work both ways. We'll plug the middle pin of our potentiometer into GPIO 26 of the PicoSure, here is the transcript formatted into paragraphs:

"And with that we are done and that looks a lot more messy and chaotic than our diagram. So whatever you need to do to manage your cables and make it look nice so that you can follow what's going on, do so.

If you have wired up these components to the same pins as I have here and according to that diagram, then you should be able to follow the rest of this chapter without any more wiring required.

So three key takeaways. One, the breadboard has power rails on the top and bottom with the inner contact points connected in rows of five. Two, voltage and current are electrical concepts with voltage being like electrical pressure and current being electrical flow. And three, a circuit using components like this must have a closed loop or it most likely won't work."