# How to Wire LEDs in Series & Parallel the Right Way

Welcome to the electrifying world of LEDs! If you’re a maker, an electronics hobbyist, a robotics enthusiast, or an animatronics builder, you’ve likely faced the challenge of how to wire multiple LEDs together. Understanding the different ways to connect LEDs—whether in series, parallel, or a combination of both in series-parallel circuits—is key to designing a circuit that best fits your project’s needs. Each of these configurations has its own unique advantages and disadvantages, impacting factors such as power requirements, brightness consistency, and resilience to component failure. This LED wiring tutorial will light your way through these circuit configurations, helping you understand how they work, when to use them, and how to build them. So, let’s switch on our learning and jump straight into the fascinating world of LED circuit design!

## What is a Series Circuit?

A series circuit is one of the simplest forms of electrical circuit that you can build. It’s called a series circuit because the components are arranged in a chain or sequence, one after the other, so there’s only one path along which the electric current can flow. You often hear this type of circuit referred to as You’ll often hear this type of circuit referred to as “daisy-chained” or “looped.”

Here’s how a series circuit works:

• Single Path: In a series circuit, there’s only one path for the current to take. If you trace a line from the positive terminal of the power supply (like a battery) to the negative terminal, you would go through each of the components in the circuit one by one.
• Constant Current: Because there’s only one path, the same current flows through all the components in the circuit. This is one of the most important properties of a series circuit. If you measure the current anywhere in the series circuit, it’ll be the same value.
• Voltage Division: The total voltage required is the sum of the forward voltages of each LED, which simplifies the power supply requirements. In a series circuit, the total voltage supplied by the power source is divided among the components. Each component gets a share of the total voltage, which is proportional to its resistance. This means that the voltage drop will be greater across the component having a higher value of resistance. Likewise, it will be the least for a component having lowest value of resistance.
• Additive Resistances: The total resistance of a series circuit is equal to the sum of the individual resistances of each component. So, if you add more components, the total resistance of the circuit increases, which decreases the total current flowing through the circuit.
• Dependent Functionality: One downside of a series circuit is that if one component fails (like a bulb burning out), it breaks the complete circuit, and all components stop working. This is because the single path for the current is interrupted.

Series circuits are used in various applications, including Christmas lights (older versions), some types of flashlights, and circuit breaker panels. In these cases, the advantages of series circuits, such as simplicity and constant current, outweigh the disadvantages.

## How to Connect LEDs in Series

Connecting LEDs in series is a straightforward process. Here’s a step-by-step guide:

1. Identify LED Terminals: Every LED has two terminals – an anode (longer lead, positive) and a cathode (shorter lead, negative).
2. Calculate the Resistor Value: It’s important to use a resistor in the circuit to limit the current and prevent the LEDs from burning out. The value of the resistor can be calculated using Ohm’s law, R = (Vs – Vf) / I, where R is the resistance, Vs is the power supply voltage, Vf is the sum of LED forward voltages, and I is the current (in Amps).

In the example pictured above, our series of four LEDs is connected to a 9V power supply (Vs). Let’s say each LED has a Vf of 2V. That would make for a total of 8V (2V + 2v + 2V + 2V = 8V). LEDs typically consume about 20mA so the I value in Amps we want for this circuit is .02A.

With these values, the formula now looks like this:

R = (9V – 8V) / .02

This gives us a resistor value of 50 Ohms. You can use more than one resistor in series to get to the value that you calculated but if you can’t get an exact match, it’s best to go a little higher. For instance, I would opt for a 68 Ohm resistor since they’re a more common value.
3. Connect the LEDs: Connect the anode of the first LED to the positive terminal of your power supply. Connect the cathode of the first LED (negative) to the anode (positive) of the second LED. Continue connecting all the LEDs in this way – cathode to anode.
4. Attach the Resistor: Connect a resistor (whose value you calculated above) either before the first LED or after the last one. It doesn’t matter whether you put it before or after the LED train and you’ll see schematics that show it both ways.
5. Double-check Connections: Review your connections to make sure they’re secure and correctly oriented.
6. Test Your Circuit: Power on your supply to test the circuit. All LEDs should light up. If not, recheck your connections and resistor calculations.

Always remember to consider the power ratings and limits of your components when designing your circuit. Using an appropriate power supply and limiting resistors will ensure that your LEDs don’t receive too much current, which can cause them to burn out.

Wiring multiple LEDs in a series configuration has both advantages and disadvantages.

### Pros of Wiring LEDs in Series:

• Uniform Current Flow: In a series circuit, the same current flows through all the LEDs, ensuring consistent brightness.
• Simple Voltage Calculation: The total voltage required is the sum of the forward voltages of each LED, which simplifies the power supply requirements.
• Less Current Consumption: A series configuration typically consumes less current than a parallel configuration, which can be more energy-efficient.

### Cons of Wiring LEDs in Series:

• Dependency on All LEDs: If one LED fails (opens or shorts), all LEDs in the series will stop functioning because the current path is interrupted.
• Higher Voltage Requirement: The power supply voltage must be greater than the sum of the forward voltages of all the LEDs in the series, which may necessitate a higher voltage power supply.
• Brightness Inconsistency: There may be minor variations in brightness if the LEDs are not identical due to manufacturing inconsistencies.

Remember that the choice between wiring LEDs in series or parallel will depend on your specific needs, the power supply you have available, and the nature of your project.

## What is a Parallel Circuit?

A parallel circuit is a type of electrical circuit where the components (such as resistors, LEDs, or other devices) are connected in parallel to each other. This means that there are multiple paths for the electrical current to flow, and each component is independently connected to the power source (like a battery or a power outlet). In a parallel circuit all the positive connections are tied together and back to the positive output of the power supply and all the negative connections are tied together and back to the negative output of the power supply.

• Multiple Paths: In a parallel circuit, there are multiple paths for the current to take. Each component is independently connected to the positive and negative terminals of the power source.
• Constant Voltage: One of the most important characteristics of a parallel circuit is that the voltage across each component is the same. This means that each component in the circuit gets the full voltage from the power source.
• Current Division: The total current supplied by the power source is divided among the components. Each component draws a current from the power source proportional to its resistance. The total current is the sum of the currents through each path.
• Resistance Reduction: When resistors are added in parallel, the total resistance of the circuit decreases. This is because the addition of more paths allows more current to flow.
• Independent Operation: Each component in a parallel circuit operates independently. If one component fails, it won’t affect the functioning of the other components. This is a significant advantage of parallel circuits over series circuits.

Parallel circuits are very common in household wiring and electronics because they allow each device to operate independently of the others. For example, in your home’s electrical system, different appliances are wired in parallel, so if your refrigerator light bulb burns out, your microwave and other appliances will still work.

## How to Connect LEDs in Parallel

Connecting LEDs in parallel is relatively straightforward. You’ll notice that I swapped the 9V battery for two AAs at 1.5V each for a total of 3V. Follow these steps to properly connect multiple LEDs in a parallel configuration:

1. Identify LED Terminals: Familiarize yourself with the two terminals of each LED: the anode (longer lead, positive) and the cathode (shorter lead, negative).
2. Calculate Resistor Value: To protect the LEDs from excessive current, you need to use resistors. Unlike connecting LEDs in series, when you connect them in parallel it’s best practice to give each LED its own resistor. Calculate the appropriate resistor value using Ohm’s law, R = (Vs – Vf) / I, where R is the resistance, Vs is the power supply voltage, Vf is the sum of LED forward voltages, and I is the current (in Amps).

In the example above, our LEDs are connected in parallel to a 3V power supply (Vs). Since each component in the circuit will receive the full voltage of the battery, using a 9V like we did in the series example is a bit overkill. Again, let’s say each LED has a Vf of 2V and that the current, I, each one consumes is 20mA, or .02A.

With these values, the formula looks like this:

R = (3V – 2V) / .02

This gives us a resistor value of 50 Ohms. The closest common resistor value is 68 Ohms. You can always add more than one resistor in series to get the exact value or jump to the closest common value that exceeds your calculations.
3. Connect Anodes to Power Supply: Connect the anode (positive) of each LED to the positive terminal of your power supply. You can use separate wires for each LED or connect the anodes together using a common wire (bus).
4. Attach Resistors: Connect a resistor to each LED either the anode (positive) or cathode (negative). Each LED should have its own resistor to ensure proper current limiting.
5. Connect Cathodes to Power Supply: Connect the cathode (negative) of each LED to the negative terminal of your power supply. Similar to the anodes, you can use separate wires for each lead or connect them together using a common wire (bus).
6. Check Connections: Review your connections to make sure they’re secure and correctly oriented.
7. Test Your Circuit: Power on your supply to test the circuit. All LEDs should light up. If not, recheck your connections and resistor calculations.

By following these steps, you can successfully connect multiple LEDs in parallel, allowing each LED to operate independently and receive the same voltage from the power supply.

Wiring multiple LEDs in parallel has its own set of advantages and disadvantages.

### Pros of Wiring LEDs in Parallel:

• Independent Operation: If one LED fails or is turned off, the rest of the LEDs in the circuit will continue to function. This is because each LED forms its own path to the power supply.
• Uniform Voltage: Each LED in a parallel circuit receives the same voltage. This ensures that all LEDs receive adequate voltage for their operation, regardless of the number of LEDs in the circuit.
• Flexibility in Power Supply Voltage: The power supply voltage needs to be equal to or slightly higher than the forward voltage of a single LED, not the sum of their forward voltages (like in series configuration). This allows the use of low-voltage power supplies.

### Cons of Wiring LEDs in Parallel:

• Varying Brightness: If there are slight differences in the forward voltage or resistance of the LEDs, some LEDs might draw more current and shine brighter than others. This could lead to inconsistent brightness across the LEDs.
• Higher Total Current: Parallel circuits draw more current from the power supply than series circuits. This is because the total current is the sum of the currents passing through each LED. If there are many LEDs, this could require a power supply with a higher current rating.
• More Complex Current Limiting: Each LED in a parallel circuit should have its own current-limiting resistor. This ensures that the same current flows through each LED. If a single resistor is used for the whole circuit, differences in individual LED characteristics can lead to uneven current distribution and potential LED damage.

When deciding whether to wire LEDs in series or parallel, it’s important to consider the characteristics of your LEDs, the specifics of your power supply, and the requirements of your application.

## Series vs. Parallel Circuits: Which One is the Best?

Ultimately, the choice between series and parallel depends on your specific needs, the resources available, and the practical constraints of your project. When choosing between wiring LEDs in series or parallel, take into account these factors to help you make the best choice:

• Power Supply Voltage: The total voltage of your power supply should align with the needs of your circuit configuration. For a series configuration, the power supply voltage should be equal to or greater than the sum of the forward voltages of all the LEDs. In contrast, for a parallel configuration, the power supply voltage should be equal to or slightly higher than the forward voltage of a single LED.
• Consistency of LED Characteristics: LEDs, even of the same type, can have minor variations in their electrical characteristics. If wired in parallel, these differences can cause uneven brightness across LEDs. On the other hand, in a series configuration, the same current flows through each LED, ensuring uniform brightness.
• Failure Impact: In a series configuration, if one LED fails, the entire circuit will stop working because the current path is broken. In a parallel configuration, LEDs function independently of each other. So, if one LED fails, the others will continue to work.
• Power Supply Current Rating: Parallel configurations draw more current because the total current is the sum of the currents through each LED. If you’re wiring many LEDs, the power supply must be capable of delivering high current. In series configurations, the same current flows through all LEDs, which means the current requirement is lower.
• Circuit Complexity: Wiring in parallel can become complex, especially when dealing with many LEDs, as each LED requires its own current-limiting resistor. In series configurations, a single resistor can be used for the entire string of LEDs, simplifying the circuit.
• Brightness Control: If individual brightness control is desired, a parallel configuration is preferable as each LED can be managed independently.

In general, for small numbers of LEDs and low power requirements, wiring in series can be simpler and more efficient. For larger numbers of LEDs, or when using a low-voltage power source, a parallel configuration may be more suitable.

## Why Not Both? Series-Parallel Circuits

A series-parallel circuit is a combination of series and parallel circuits. In this type of circuit, some components are wired in series and others are wired in parallel. This configuration allows for more complex designs and can offer the advantages of both series and parallel circuits. For example, you might have two sets of LEDs, with the LEDs in each set connected in series, and the two sets connected in parallel with each other.

Series-parallel circuits can be more complex to analyze and design than simple series or parallel circuits, but they offer greater flexibility and can be used to achieve a wide range of behaviors and performance characteristics in an electronic system. To analyze a series-parallel circuit, you typically start by analyzing the series circuits and parallel circuits separately, then combine the results. This often involves using basic circuit laws like Ohm’s law and Kirchhoff’s laws.

## How to Connect LEDs in Series-Parallel

Connecting two or more sets of LEDs in a series-parallel configuration involves wiring some LEDs in series, and then connecting these series sets in parallel.

In the example above, we have two sets of four LEDs wired in series and then these two sets are wired together in parallel.

Here’s how to wire your own series-parallel circuit:

1. Identify LED Terminals: First, identify the two terminals of each LED: the anode (longer lead, positive) and the cathode (shorter lead, negative).
2. Calculate Resistor Value: For each series set, calculate the appropriate resistor value using Ohm’s law, R = (Vs – Vf) / I, where R is the resistance, Vs is the power supply voltage, Vf is the sum of LED forward voltages, and I is the current (in Amps).

In the example circuit above, each series of four LEDs is connected to a 9V power supply (Vs). Let’s say each LED has a Vf of 2V. That would make for a total of 8V (2V + 2v + 2V + 2V = 8V) per set. LEDs typically consume about 20mA so the I value in Amps we want for this circuit is .02A.

With these values, the formula now looks like this:

R = (9V – 8V) / .02

This gives us a resistor value of 50 Ohms. Since 68 Ohms is the closest common value that goes above the minimum requirement, we’ll use that.
3. Connect LEDs in Series: For each set, connect the anode of the first LED to the positive terminal of your power supply, then connect the cathode of the first LED to the anode of the next LED. Repeat until all LEDs in the set are connected.
4. Attach Resistors: Connect a resistor to either the anode of the first LED in each series set or the cathode of the last LED in each series set.
5. Connect Series Sets in Parallel: Now, connect the negative leads (the other side of the series set) to the negative terminal of your power supply. Each series set should now be connected in parallel to the others.
6. Check Connections: Review your connections to make sure they’re secure and correctly oriented.
7. Test Your Circuit: Power on your supply to test the circuit. All LEDs should light up. If not, recheck your connections and resistor calculations.

By following these steps, you can successfully connect multiple sets of LEDs in a series-parallel configuration. This configuration can offer the advantages of both series and parallel circuits, including balanced brightness, independent operation of each set, and the ability to use a power supply with a voltage close to the forward voltage of a single series set.

Series-parallel circuits combine the advantages of both series and parallel circuits, but they also come with their own set of pros and cons.

### Pros of Series-Parallel Circuits:

• Flexibility: Series-parallel circuits allow for more complex designs and provide greater flexibility. They can be tailored to meet specific needs by combining components in different series and parallel configurations.
• Balanced Load: They enable better control over the current and voltage distribution across the circuit. For example, LEDs in a series-parallel circuit can have balanced brightness if the LEDs and resistors are well-matched.
• Independent Sub-Circuits: If a component within one series string fails, only that string goes out. The other strings (parallel paths) continue to function, unlike a pure series circuit where failure of one component will disrupt the entire circuit.

### Cons of Series-Parallel Circuits:

• Complexity: Series-parallel circuits can be more complex to design and analyze. Calculating total resistance, current, and voltage drop can require more steps compared to pure series or parallel circuits.
• Variable Load: If the components within the series strings are not identical, there can be uneven distribution of current, leading to differences in brightness in the case of LEDs.
• Failure Impact: While a failure in one series string won’t disrupt the whole circuit, it will disrupt the balance of current and voltage in the remaining parts of the circuit, possibly causing other components to overheat or fail.

From adding LEDs to props and costumes to illuminated control panels and robot lighting, understanding how to wire multiple LEDs together using series, parallel, and series-parallel circuits is a powerful tool in the arsenal of any maker, electronics hobbyist or professional, roboticist, or animatronics builder. Each configuration presents its own unique set of advantages and trade-offs, influencing factors like power requirements, brightness uniformity, and resilience in the face of component failure. By considering these factors and aligning them with your project’s specific needs, you can design an optimal LED circuit that truly shines. Remember, the best circuit for your project depends on your individual needs and constraints, and sometimes the brightest solutions emerge from a mix of series, parallel, and series-parallel configurations. Keep experimenting, stay illuminated, and happy building!