i'm going to show you how to design and make your very own version of this circuit board it's perfect for learning electronics and you can even download my design files for free and order the circuit board yourself links down in the video description for that for the power supply i will use some standard 1. 5 volt batteries i will use this battery holder to combine them to create a 3 volt supply for the circuit board the multimeter shows slightly more than three volts as the batteries are new for the lights we have two main options the standard through-hole leds or smd type leds which stands for surface mount device we can see a standard led here and next to it is an smd led i'll zoom in so you can see it here you can see it next to a scale so you can really see just how tiny these components are however it can produce a good amount of light so i will use five of these as that will keep the circuit board simple but also fairly small the smd leds are tricky to handle so you'll need some tweezers for that my top tip is to handle them on a flat dark colored surface because if you drop them on a carpet you're probably never going to find them again as a quick test how many objects can you see in this carpet tell me the grid reference for them and let me know your answers in the comment section down below the smd led typically has a small dot on the top although you might need a microscope to see this but sometimes the manufacturer uses this to indicate the anode and other times it's used to indicate the cathode so always check with a manufacturer's data sheet or you can test it yourself here you can see that this led illuminates when the positive is connected to the dot on the back you should find a symbol also again this could be either the anode or the cathode so check the data sheet or test it here we can see the led illuminates when it's connected like this to find the led we're going to go to a suppliers website and search through their components i like these ones because they have a pcb footprint which we can use later in the design we can also see that this led has an orange light it has a forward current of 20 milliamps and a forward voltage of 1. 9 volts importantly the forward voltage is less than the 3 volt supply we're going to use that makes our circuit board design very easy so now we have two options we can connect the leds in series or parallel if we connect them in series then each led is going to remove an additional 1.
9 volts so that means we need around 9. 5 volts of power supply to the circuit board to be able to power them all so we can't use this method we will instead connect them in parallel so that each led receives the same voltage then we would only need a supply of 1. 9 volts however we will be using the 3 volt supply by the way we have covered series and parallel circuits in detail in our previous video links down below for that now if we provide an led with 3 volts and it's only rated to handle 1.
9 volts then we're going to destroy it too much current is going to flow through the component and it will burn out so we need a resistor to limit the current and remove that excess voltage what size resistor do we need well we have a 3 volt supply and the led has a voltage drop of 1. 9 volts so if we subtract this from the power supply then we have to reduce the voltage by 1. 1 volts the leds are rated for 20 milliamps or 0.
02 amps so 1. 1 volts divided by 0. 02 amps gives us a resistance of 55 ohms and by the way we have also covered ohm's law in detail previously links down below for that so we also need to know the power rating of the resistor we calculate that from the current of 0.
02 amps squared multiplied by 55 ohms which gives us 0. 022 watts and that is a very small amount which is a good thing because that's how much energy we're wasting as heat from the resistor to remove that excess 1. 1 volts we basically convert the energy into heat to remove it okay so we want to use smd components so we search the supplier website and i will use this one it is rated for 56 ohms so it's slightly higher than we need but close enough it has a tolerance of one percent meaning it could be anything between 55.
44 ohms or 56. 56 ohms when i test this one it's showing 56. 3 ohms we can also see that this resistor is able to handle up to 125 milliwatts which is much higher than our 22 milliwatt design and this component also has a drawing as well which we can use in our design so we will use this component these resistors are also incredibly small so you'll need some tweezers to handle them we don't need to worry about the polarity because they will work either way we connect them so we have five leds in parallel with a resistor connected to each one next we need a way to connect the battery pack to the circuit we could just solder them but i'm going to use a terminal block so that we can easily connect to different power sources in the future if we needed to we only need a positive and ground connection so we will use this model right here now to design the circuit board we're going to be using our team designer who have kindly sponsored this video all of our viewers can get a free trial of the software and i will leave a link for you in the video description down below so do check that out so we start a new project and then we add in the symbols of the components we found i use an add-on to do that just input the part number we only have three components the led the resistor and the connector we join the led and resistor and then we duplicate it then we connect the resistors together and then we join it to the connector then we connect the leds together and we join that to the connector also then we define the ground and positive points of the circuit next we just add some annotations to the board and then go to the pcb layout and import the components drag the connector into place i'd also say check it in 3d to ensure it's facing the correct way and then move the leds into position and align them next move the resistors into place and align them also you can move the text if you wish i'll also add some holes so that we can mount the circuit board in future if we needed to and then i'll adjust the position of the components then we just define the positive and ground ports on the board and now we start to draw the roots between the components we connect the resistors and the led first then all the resistors together and connect that to the positive port then connect all the leds together and connect them to the ground port finally set your polygon and the pcb now looks like this so we can export the project to order the pcb we just head to jlcpcb who have also kindly sponsored this video they offer exceptional value with five circuit boards from just two dollars i'll leave a link for you in the video description down below do check that out and also don't forget you can download my circuit board design file for free links down below for that so we upload our gerber files and check the preview it looks good so we can then set the color although i will stick with green and then i'll head to the checkout a few days later our circuits arrive in the post and we can start building this circuit so get your components ready we will use some solder paste and you can buy this online i will leave a link for you in the video description now unless you have incredible vision which i do not you will need a microscope or you could use your smartphone to zoom in and see the board and components so all we need to do is put a small amount of paste onto each of the solder pads on the board then we start to add the components i'll add the resistors first as they are the easiest you'll need some tweezers to get them positioned correctly and also push them into the paste and then it should look something like this now for the leds make sure you align them correctly and to do that you'll need to check the manufacturer's datasheet so we just align the leds the correct way until it looks something like this now we need a heat gun and i'll be using this one here i typically set it to around 300 to 400 degrees celsius depending on the components being used and it also has a medium wind speed then we slowly move the heat gun around so that the solder begins to melt it will lock all the components into place and it should leave you with a very nice finish so we should then have a circuit board that looks like this then we just need to solder the power connection to the board and we end up with something like this now we just connect the battery pack to the board and then we insert the batteries and the board lights up and you can even add a switch if you like so there we have it our very own simple circuit board light using smd and throughput components check out one of the videos on screen now to continue learning about electronics engineering and i'll catch you there for the next lesson don't forget to follow us on facebook tick tock linkedin instagram and the engineeringmindset.
