ClassX Video Lessons Youtube Channel The Engineering Mindset Multi-LED circuit design – LED Parallel Circuits
When designing circuits with LEDs (Light Emitting Diodes), it’s important to understand how to manage voltage and current to ensure the LEDs work properly. Let’s explore how to connect multiple LEDs to a power source, like a 9-volt battery, and make sure they light up without any issues.
Imagine you want to connect 6 LEDs to a 9-volt battery. Each LED has a voltage drop of 2 volts and needs 20 milliamps of current to function. If you connect them directly to the battery, each LED would receive 9 volts, which is too much. To fix this, you need to add a resistor in series with each LED.
Here’s how you calculate the resistor value:
Next, determine the power rating of the resistor:
Now, calculate the total current for all 6 LEDs:
A 9-volt battery typically has a capacity of about 500 milliamp-hours. With a current draw of 120 milliamps, the battery will last approximately 4 hours.
If you want to add more LEDs, you can place multiple LEDs in series on each branch. For example, if you put 3 LEDs on each branch, the voltage drop across the LEDs would be 6 volts (3 LEDs × 2 volts each). This leaves 3 volts to drop across the resistor:
The total current in each branch remains the same, so you can keep adding LEDs until you reach the maximum voltage capacity.
If you want to use LEDs of different colors, each with different voltage drops, you need to calculate the resistor for each type. For example:
The total current for these LEDs would be 60 milliamps, giving the battery a runtime of about 8 hours.
Another method is to connect LEDs in parallel, using a single resistor to limit the total current. This works best when using LEDs of the same color or rating. For instance, if you have 3 red LEDs, each with a 2-volt drop and needing 20 milliamps, you can calculate the resistor as follows:
Using LEDs with different voltage requirements in parallel can cause issues, as they may not light up properly due to insufficient voltage.
Understanding how to calculate resistor values and manage current is crucial for designing effective LED circuits. Whether connecting LEDs in series or parallel, these principles will help ensure your LEDs shine brightly and efficiently. Keep exploring electronics to deepen your understanding and skills!
Gather materials such as a breadboard, a 9-volt battery, LEDs, resistors, and connecting wires. Follow the instructions to build a simple LED circuit in series. Calculate the resistor values needed to ensure the LEDs function correctly. This hands-on activity will help you understand the practical aspects of circuit design.
Use LEDs of different colors and calculate the appropriate resistor for each based on their voltage drop. Connect them in parallel and observe how the different voltage requirements affect the circuit. Document your observations and explain why some LEDs might not light up as expected.
Create a design for a multi-LED display using both series and parallel connections. Plan the layout, calculate the necessary resistor values, and estimate the battery life. Present your design to the class, explaining your choice of connections and the expected performance of the display.
Given a set of LEDs and a power source, calculate how long the battery will last. Use different configurations and resistor values to see how they affect the battery life. Share your findings with the class and discuss strategies to optimize battery usage in LED circuits.
Use an online circuit simulation tool to design and test LED circuits. Experiment with different configurations, resistor values, and LED colors. Analyze the simulation results to understand how changes in the circuit affect the performance. This will help reinforce your understanding of LED circuit design principles.
Here’s a sanitized version of the provided YouTube transcript:
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This design allows us to use different colored LEDs, although it’s easier to calculate if they are all the same color. Let’s say we want to connect 6 LEDs to a 9-volt battery. Each LED has a voltage drop of 2 volts and requires 20 milliamps. The entire rail is 9 volts, and the other rail is 0 volts, so each LED will get 9 volts across it, which is obviously too much. Therefore, we need to place a resistor in series with each LED.
We start with 9 volts and subtract the 2 volts for the LED, leaving us with 7 volts. We need to drop 7 volts across each branch. We calculate the resistor value by dividing 7 volts by 0.02 amps, which equals 350 ohms. Next, we find the power rating: 0.02 amps squared multiplied by 350 ohms gives us 0.14 watts, so a quarter-watt resistor will be used.
Now, we need to add up all the currents in each branch. 0.02 amps multiplied by 6 LEDs gives us 0.12 amps. A 9-volt battery has a capacity of around 500 milliamp-hours, and our circuit is using 120 milliamps. Dividing 500 by 120 gives us around four hours of runtime.
We can see that there is still enough voltage on each branch to connect more LEDs. If we place three LEDs on each branch, each branch will have a reduction of 6 volts. Therefore, 9 volts minus 6 volts equals a 3-volt drop across the resistor. So, 3 volts divided by 0.02 amps gives us a 150-ohm resistor. Notice that the total current in each branch didn’t increase, so we can add more LEDs until the maximum voltage is reached.
If we want to use different colored LEDs, we can place them on different branches and find the suitable resistor for each. For example, we might have a red, blue, and green LED. Each LED has the same current requirement of 20 milliamps, but the red LED has a voltage drop of 2 volts, the blue has 3.4 volts, and the green has 3 volts.
The resistor for the red LED is calculated as follows: 9 volts minus 2 volts gives us 7 volts. Dividing 7 volts by 0.02 amps results in a 350-ohm resistor. For the blue LED, 9 volts minus 3.4 volts leaves us with 5.6 volts, so 5.6 volts divided by 0.02 amps gives us a 280-ohm resistor. For the green LED, 9 volts minus 3 volts leaves us with 6 volts, and 6 volts divided by 0.02 amps gives us a 300-ohm resistor. The total current is therefore 60 milliamps, so the battery will last around 8 hours.
Another way to connect LEDs is by connecting them in parallel and using a single resistor to limit the total current. For this design, you should only use LEDs of the same color or rating.
Let’s say we have a 9-volt battery and 3 red LEDs, all with the same voltage drop of around 2 volts and each requiring 20 milliamps of current. We add the currents together to get 60 milliamps, which will flow through this one resistor. Since they are connected in parallel, they will all have the same voltage difference across them.
We calculate the resistor by taking 9 volts minus 2 volts, which equals 7 volts. Since all the current flows through this one resistor, we divide 7 volts by 60 milliamps, resulting in a 116-ohm resistor. The power calculation comes out to 0.49 watts, so a half-watt resistor will be used.
The reason we need to use the same rating LEDs is that the voltage difference across them is just 2 volts. If we use LEDs with different ratings, they may not illuminate properly. For example, if we place a blue LED in the circuit, it requires a higher voltage, which may not be sufficient, causing it not to turn on.
That’s it for this video! To continue learning about electronics and electrical engineering, check out one of the videos on screen now, and I’ll catch you in the next lesson. Don’t forget to follow us on social media and visit theengineeringmindset.com.
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This version maintains the technical content while removing informal language and ensuring clarity.
LEDs – Light Emitting Diodes, which are semiconductor devices that emit light when an electric current passes through them. – Example sentence: LEDs are commonly used in electronic devices for indicator lights because they are energy-efficient and have a long lifespan.
Voltage – The electric potential difference between two points, which causes current to flow in a circuit. – Example sentence: The voltage across the battery terminals determines how much energy is available to push electrons through the circuit.
Current – The flow of electric charge in a circuit, typically measured in amperes. – Example sentence: When the switch is closed, the current flows through the circuit, powering the connected devices.
Resistor – An electrical component that limits or regulates the flow of electrical current in a circuit. – Example sentence: A resistor is used in the circuit to reduce the current and prevent damage to sensitive components.
Series – A type of circuit configuration where components are connected end-to-end, so the same current flows through each component. – Example sentence: In a series circuit, if one bulb burns out, the entire string of lights will go out because the current path is interrupted.
Parallel – A type of circuit configuration where components are connected across common points, allowing multiple paths for the current to flow. – Example sentence: In a parallel circuit, each bulb operates independently, so if one bulb fails, the others remain lit.
Battery – A device consisting of one or more electrochemical cells that store and provide electrical energy. – Example sentence: The battery in the remote control provides the necessary power to transmit signals to the television.
Ohms – The unit of electrical resistance, symbolized by the Greek letter omega (Ω). – Example sentence: The resistance of the resistor is measured in ohms, which indicates how much it opposes the flow of current.
Power – The rate at which electrical energy is transferred by an electric circuit, typically measured in watts. – Example sentence: The power consumed by an electrical device can be calculated by multiplying the voltage by the current.
Circuits – Closed loops or pathways that allow electric current to flow, enabling the operation of electronic devices. – Example sentence: Engineers design circuits to efficiently distribute electrical power to various components in a device.
