ClassX Video Lessons Youtube Channel The Engineering Mindset LED Dimmer controller design – Electronics engineering pulse width modulation
In this article, we’ll explore how to design a circuit that allows you to dim LED strip lights. We’ll cover the working principles, the design process, and how to create a professional-looking printed circuit board (PCB). By the end, you’ll have the knowledge to build your own LED dimmer controller.
We’ll be using SMD 5050 LED strips, known for their low current demand and excellent illumination. These strips are wired in parallel, allowing you to cut them to your desired length. For this project, we’ll use 81 LEDs divided into nine strips of nine LEDs each. By soldering short lengths of wire, we connect positive to positive and negative to negative, forming an LED panel.
When connected to a 12V power supply, the panel draws about 1.3 amps. As you reduce the voltage, the lights dim, and the current decreases. While a manual switch can turn the lights on and off, we’ll use a MOSFET to automate this process. The IRFZ44N MOSFET is ideal due to its ability to handle the voltage and current with low resistance.
We’ll use Altium Designer for this project, a powerful tool for PCB design. Begin by starting a new project and adding components like the MOSFET, which can be sourced from suppliers like Mouser. Include terminal blocks for the power supply, switch, and LED strip light.
Connect the power supply terminal to ground and the positive terminal to the switch. The switch output links to the LED terminal, while the LED return terminal connects to the MOSFET’s drain pin. The MOSFET source pin connects to ground. To control the MOSFET, we’ll generate a pulse width modulation (PWM) signal using a 555 timer.
The 555 timer is an integrated circuit that simplifies our design. It has eight pins, each serving a specific function. The MOSFET typically blocks current flow, but applying a voltage to the gate pin allows current to pass, lighting up the LED. The higher the voltage, the brighter the LED.
The 555 timer sends pulses from pin 3 to the MOSFET. Each pulse has an on and off period, creating an average voltage. A wider on pulse results in a higher average voltage, allowing more current through the MOSFET and brightening the LED.
Pin 8 of the 555 timer connects to the power supply, and pin 1 connects to ground. Pin 4 is the reset pin, which should remain powered. Pin 5 connects to ground via a 0.1 microfarad ceramic capacitor to filter noise. Pin 3, the output, connects to the MOSFET, with a 1 kΩ resistor to limit current and protect the timer.
To turn the MOSFET off, we need to discharge the stored charge, so we place a 10 kΩ resistor to ground. Inside the 555 timer, three 5 kΩ resistors in series between pins 8 and 1 divide the voltage, providing reference voltages for two comparators.
The comparators compare these voltages and output a high or low signal. Pins 2 and 6 are connected to ensure equal voltage. The comparator outputs connect to a flip-flop, which sends a high or low signal based on the inputs.
This signal passes through an inverter, which inverts it. By applying a small voltage to pins 2 and 6, we set the timing interval. The flip-flop output controls a transistor that manages current flow from the capacitor to ground. This cycle repeats, creating a PWM signal. We use a 10 nanofarad capacitor, but a larger one could decrease frequency, though excessively large capacitors lead to impractical cycles.
After assembling a prototype to test functionality, we can adjust brightness. Finalize the PCB design by importing components into the PCB design file, arranging them, defining the board shape, adding annotations, and generating routes to connect everything. After verifying the routes, create the polygon and export Gerber files.
We’ll use JLCPCB to print our circuit board, offering great value with five boards starting at just $2. After uploading Gerber files and customizing the design, proceed to checkout and submit the order.
Once the circuit board arrives, solder the components, starting from the center and working outward. After a few minutes, you’ll have a well-assembled circuit board. Connect the lights and power supply, flip the switch, and adjust the potentiometer to control brightness.
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Assemble a basic LED dimmer circuit using a breadboard, MOSFET, and 555 timer. This activity will help you understand the physical connections and components involved in creating a PWM signal for LED dimming. Pay close attention to the connections and test the circuit to see the dimming effect in action.
Use Altium Designer to create a PCB layout for your LED dimmer circuit. Follow the steps outlined in the article to import components, arrange them, and generate routes. This exercise will enhance your skills in PCB design and familiarize you with professional design software.
Utilize an oscilloscope to analyze the PWM signal generated by the 555 timer in your circuit. Observe the changes in the duty cycle as you adjust the potentiometer and understand how this affects the brightness of the LEDs. This will deepen your understanding of PWM and its practical applications.
Research and source the necessary components for the LED dimmer circuit from suppliers like Mouser or Digi-Key. Compare prices, availability, and specifications to make informed purchasing decisions. This activity will improve your ability to navigate electronic component marketplaces.
Use a circuit simulation tool like LTSpice or Proteus to simulate your LED dimmer circuit. Identify potential issues and troubleshoot them within the simulation environment before building the physical circuit. This will enhance your problem-solving skills and prepare you for real-world circuit design challenges.
Here’s a sanitized version of the provided YouTube transcript, with unnecessary filler words and informal language removed for clarity:
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This circuit allows us to dim LED strip lights. I will show you how the circuit works, how to design one, and how to turn it into a professional-looking printed circuit board. You can download a copy of my circuit board and build your own; I’ll leave a link in the video description.
I will be using SMD 5050 LED strips, which have a relatively low current demand and provide good illumination. These are wired in parallel, so we can cut them to the desired length—just ensure you cut along the marked cut line. I will use 81 LEDs split into nine strips of nine LEDs. To connect them, we cut short lengths of wire and solder them, connecting positive to positive and negative to negative. This will give us an LED panel.
When we connect this to a 12V power supply, it draws approximately 1.3 amps. As we reduce the voltage, the lights become dimmer, and the current also reduces. We can use a switch to manually turn them on and off, but instead, we can use a MOSFET, which acts as an electronic switch to automate this process, allowing us to turn them on and off hundreds or even thousands of times per second by applying a voltage to the gate pin. I will use an IRFZ44N MOSFET because it can handle the voltage and current and has a low drain-source on-resistance.
For this tutorial, we will use Altium Designer, who has kindly sponsored this video. All viewers can get a free trial of this software using the link in the video description. We start a new project and add the components. I found the MOSFET on a supplier’s website, Mouser, and added it to the design. I will also add terminal blocks for the power supply, switch, and LED strip light.
We connect the power supply terminal to ground and the positive terminal to the switch. The switch output connects to the LED terminal, and the LED return terminal connects to the MOSFET drain pin. The MOSFET source pin connects to ground. To control the MOSFET, we will use a pulse width modulation (PWM) signal, which can be generated using a 555 timer.
The 555 timer is an integrated circuit that simplifies our design. It has eight pins used for different purposes. The MOSFET normally blocks the flow of current, but applying a voltage to the gate pin allows current to flow, illuminating the LED. The higher the voltage applied, the more current flows, and the brighter the LED shines.
The 555 timer provides the voltage to the MOSFET from pin 3, sending pulses. Each pulse has an on and off period, allowing the MOSFET to experience an average voltage. The wider the on pulse, the higher the average voltage, allowing more current to flow through the MOSFET, making the LED shine brighter.
Pin 8 of the 555 timer connects to the power supply, and pin 1 connects to ground. Pin 4 is a reset pin, which we want to keep powered. Pin 5 connects to ground via a 0.1 microfarad ceramic capacitor to filter out noise. Pin 3 is the output, which connects to the MOSFET. To protect the 555 timer, we place a 1 kΩ resistor here to limit current.
When the MOSFET is turned on, a small amount of charge is stored. We need to discharge this to turn the MOSFET off, so we place a 10 kΩ resistor to ground. Inside the 555 timer, we have three 5 kΩ resistors in series between pins 8 and 1. With around 12V from the power supply at pin 8, each resistor drops 1/3 of the voltage, giving us 8 volts and 4 volts.
These voltages are used as references for two comparators. The first comparator connects to the resistors through the negative input, while the positive input connects to pin 6 (the threshold pin). The second comparator connects to the resistors via the positive input, with its negative input connected to pin 2 (the trigger pin). The comparators compare the two voltages and output a high or low signal accordingly.
We connect pins 2 and 6 together to ensure the voltage is the same. The output from the comparators connects to a flip-flop. The first comparator connects to the reset input, and the second connects to the set input. The flip-flop outputs a high or low signal based on the inputs from the comparators.
This signal passes through an inverter, which inverts the signal. By applying a small voltage to pins 2 and 6, we can set the timing interval. The output of the flip-flop controls a transistor that manages the flow of current from the capacitor to ground. When the flip-flop output is low, the transistor is off, allowing the capacitor to charge. When the voltage reaches a certain level, the flip-flop output becomes high, turning the transistor on and discharging the capacitor.
This cycle repeats continuously, creating a PWM signal. We use a 10 nanofarad capacitor, but we could use a larger one to decrease the frequency. However, using a very large capacitor would result in impractically long cycles.
After building a simple prototype to check functionality, I can adjust the brightness. We will finish the PCB design by importing the components into the PCB design file and arranging them. We define the board shape, add annotations, and generate the routes to connect everything. After checking the routes, we create the polygon and export our Gerber files.
We will use JLCPCB to print our circuit board. They offer exceptional value, with five circuit boards starting at just $2. I will leave a link in the video description. After uploading our Gerber files and customizing the design, we proceed to checkout and submit the order.
A few days later, our circuit board arrives. We start soldering the components to the board, beginning from the center and working outward. After a few minutes, we have a well-assembled circuit board.
Next, we connect the lights and power supply, flip the switch, and adjust the potentiometer to control the brightness. Check out one of the videos on screen now to continue learning about electronics engineering. Don’t forget to follow us on social media and visit theengineeringmindset.com.
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This version maintains the technical details while improving readability and clarity.
LED – A semiconductor device that emits light when an electric current passes through it. – Example sentence: The LED in the circuit was used to indicate the power status of the device.
Dimmer – An electronic device used to adjust the brightness of a light source by altering the voltage waveform applied to it. – Example sentence: The dimmer was integrated into the lighting system to allow for adjustable ambient lighting in the room.
Circuit – A complete and closed path through which electric current can flow. – Example sentence: The engineer designed a complex circuit to control the robotic arm’s movements.
PWM – Pulse Width Modulation, a technique used to encode a message into a pulsing signal by varying the width of the pulses. – Example sentence: PWM was utilized to control the speed of the DC motor in the project.
MOSFET – Metal-Oxide-Semiconductor Field-Effect Transistor, a type of transistor used for amplifying or switching electronic signals. – Example sentence: The MOSFET was chosen for the amplifier circuit due to its high efficiency and fast switching capabilities.
Timer – An electronic device or circuit that counts time intervals and is used to control the operation of a system. – Example sentence: The timer was set to activate the heating element every morning at 6 AM.
Voltage – The electrical potential difference between two points, which drives the flow of current in a circuit. – Example sentence: The voltage across the resistor was measured to ensure it was within the safe operating range.
Current – The flow of electric charge in a conductor, typically measured in amperes. – Example sentence: The current flowing through the circuit was too high, causing the fuse to blow.
Design – The process of planning and creating a system or component to meet desired needs and specifications. – Example sentence: The design of the new microcontroller included advanced features for improved performance.
Electronics – The branch of physics and engineering concerned with the study and application of electronic devices and circuits. – Example sentence: The course on electronics covered topics such as semiconductors, transistors, and integrated circuits.
