ClassX Video Lessons Youtube Channel The Engineering Mindset Design and Build a PCB – SMD LED Learn electronics engineering
In this guide, we’ll explore how to design and create your own circuit board using SMD (Surface Mount Device) LEDs. This project is a fantastic way to dive into electronics engineering, and you can even download the design files for free to order your own circuit board. Let’s get started!
We’ll use standard 1.5-volt batteries, combined in a battery holder to provide a 3-volt supply for our circuit board. A multimeter will confirm that the new batteries deliver slightly more than 3 volts.
For lighting, we have two options: standard through-hole LEDs or SMD LEDs. SMD LEDs are tiny but powerful, making them ideal for a compact circuit board. We’ll use five SMD LEDs, and you’ll need tweezers to handle these small components. A tip: work on a flat, dark surface to avoid losing them.
SMD LEDs often have a small dot on top, indicating either the anode or cathode. Always check the manufacturer’s datasheet or test the LED to determine the correct polarity. In our case, the LED lights up when the positive is connected to the dot.
We’ll select an LED with an orange light, a forward current of 20 milliamps, and a forward voltage of 1.9 volts. Since our power supply is 3 volts, this setup simplifies our circuit design.
Connecting LEDs in series would require a higher voltage supply, so we’ll connect them in parallel. This way, each LED receives the same voltage, and we only need a 1.9-volt supply. However, we’ll use a 3-volt supply, so we need a resistor to prevent the LEDs from burning out.
To find the right resistor, subtract the LED’s forward voltage (1.9 volts) from the power supply (3 volts), leaving 1.1 volts to be reduced. Using Ohm’s Law, divide 1.1 volts by the LED’s current (0.02 amps) to get a resistance of 55 ohms. The resistor’s power rating is calculated as 0.02 amps squared times 55 ohms, resulting in 0.022 watts.
We’ll use a 56-ohm resistor, which is close enough to our calculated value. It has a tolerance of one percent and can handle up to 125 milliwatts, well above our design’s requirement. These resistors are small, so tweezers are necessary for handling.
Our circuit will have five LEDs in parallel, each with a resistor. We’ll use a terminal block to connect the battery pack, allowing flexibility for future power sources. The design process involves using a PCB design software, where we add component symbols, connect them, and define ground and positive points.
In the PCB layout, we import components, position them, and draw routes between them. We connect resistors and LEDs, define positive and ground ports, and add mounting holes if needed. Once the layout is complete, we export the project to order the PCB.
We can order the PCB from a supplier, upload the Gerber files, and customize options like color. Once the PCBs arrive, we use solder paste and a heat gun to attach components. Align LEDs correctly using the datasheet, and carefully solder the power connection.
After assembling the circuit board, connect the battery pack, insert the batteries, and watch your board light up. You can even add a switch for convenience.
Congratulations! You’ve successfully designed and built a simple circuit board using SMD and through-hole components. Keep exploring electronics engineering, and check out more resources to continue your learning journey.
Familiarize yourself with PCB design software by participating in a hands-on workshop. You’ll learn how to add component symbols, connect them, and define ground and positive points. This activity will help you understand the intricacies of designing a circuit board layout.
Practice handling and soldering SMD LEDs using tweezers and a heat gun. This activity will enhance your dexterity and precision, crucial skills for working with small electronic components. Ensure you work on a flat, dark surface to prevent losing any parts.
Engage in a challenge where you calculate the appropriate resistor values for different LED configurations. Use Ohm’s Law to determine the resistance needed to prevent LEDs from burning out. This exercise will reinforce your understanding of electrical calculations.
Create Gerber files from your PCB design and simulate the ordering process with a supplier. Customize options like color and material. This activity will give you practical experience in preparing and submitting files for PCB manufacturing.
Assemble your circuit board by attaching components with solder paste and a heat gun. Test your board by connecting the battery pack and observing the LEDs light up. This session will culminate your learning experience, allowing you to see your design in action.
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 are down in the video description for that.
For the power supply, I will use standard 1.5-volt batteries. I will use a battery holder to combine them to create a 3-volt supply for the circuit board. The multimeter shows slightly more than 3 volts as the batteries are new.
For the lights, we have two main options: standard through-hole LEDs or SMD (surface mount device) LEDs. We can see a standard LED here, and next to it is an SMD LED. I’ll zoom in so you can see just how tiny these components are. However, they can produce a good amount of light, so I will use five of these to 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. 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; again, this could be either the anode or the cathode, so check the data sheet or test it.
To find the LED, we’re going to go to a supplier’s website and search through their components. I like these ones because they have a PCB footprint that we can use later in the design. We can also see that this LED has an orange light, 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, which makes our circuit board design very easy.
Now we have two options: we can connect the LEDs in series or parallel. If we connect them in series, then each LED will remove an additional 1.9 volts, meaning we would need around 9.5 volts of power supply 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 are down below for that. 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 will 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? We have a 3-volt supply, and the LED has a voltage drop of 1.9 volts. If we subtract this from the power supply, we need 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. By the way, we have also covered Ohm’s law in detail previously; links are down below for that.
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. 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’s website and I will use this one. It is rated for 56 ohms, which is 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 can handle up to 125 milliwatts, which is much higher than our 22-milliwatt design. This component also has a drawing 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 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 need 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. We start a new project and then 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 duplicate it. Then we connect the resistors together and join them to the connector. Next, we connect the LEDs together and join that to the connector as well. 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 as well. You can move the text if you wish. I’ll also add some holes so that we can mount the circuit board in the future if needed, and then I’ll adjust the position of the components. Then we just define the positive and ground ports on the board.
Now we start to draw the routes 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, so 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 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, insert the batteries, and the board lights up. You can even add a switch if you like.
So there we have it: our very own simple circuit board light using SMD and through-hole 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 social media and visit theengineeringmindset.com.
PCB – A printed circuit board, which mechanically supports and electrically connects electronic components using conductive tracks, pads, and other features etched from copper sheets laminated onto a non-conductive substrate. – The engineering students spent the afternoon designing a PCB for their robotics project.
LEDs – Light Emitting Diodes, which are semiconductor devices that emit light when an electric current passes through them. – The new laboratory equipment uses LEDs to indicate the operational status of the device.
Circuit – A closed loop that allows current to flow, consisting of various electrical components such as resistors, capacitors, and transistors. – In the electronics lab, we learned how to build a simple circuit using a breadboard and basic components.
Resistor – An electrical component that limits or regulates the flow of electrical current in an electronic circuit. – The professor explained how to calculate the resistance needed for a resistor to protect the LED from excessive current.
Voltage – The electrical potential difference between two points in a circuit, which drives the flow of current. – Understanding how to measure voltage across components is crucial for diagnosing circuit issues.
Supply – A source of electrical power, often referring to a power supply unit that provides the necessary voltage and current to a circuit. – The laboratory is equipped with adjustable power supplies to test various electronic circuits.
Design – The process of planning and creating a system or component to meet desired needs and specifications, often involving schematic diagrams and simulations. – The final project for the course required students to design a functional amplifier circuit.
Components – Individual parts or elements that make up an electronic circuit, such as resistors, capacitors, diodes, and transistors. – Identifying and understanding the function of each component is essential for successful circuit assembly.
Engineering – The application of scientific and mathematical principles to design and build machines, structures, and other items, including electronic systems. – The engineering department offers a comprehensive program in electrical engineering, focusing on both theory and practical applications.
Current – The flow of electric charge in a circuit, typically measured in amperes. – During the experiment, we observed how the current changes when different resistors are added to the circuit.
