When using LED products, in addition to the most common connection methods known as common anode configuration and common cathode configuration, there is another less well-known method. This article will introduce these three common connection methods and explain to the readers why LED connection methods are necessary. Examples of some of these methods will also be provided.
Table of Contents
The three most common LED connection methods.
There are approximately three different LED connection methods commonly found in various products:
- Direct configuration
- Common anode configuration
- Common cathode configuration
Let’s discuss each of these methods separately.
Direct configuration
The direct configuration is the most basic way to light up an LED, and it only requires the following four conditions for the LED to illuminate:
- Connect the positive terminal of the LED to a higher voltage.
- Connect the negative terminal of the LED to a lower voltage.
- Ensure that the voltage difference between the positive and negative terminals of the LED is slightly higher than the forward voltage of the LED (excessive voltage can cause damage).
- Ensure that the current passing through the LED is less than the maximum current it can withstand (excessive current can cause damage).
These four conditions are necessary for illuminating an LED. In the direct configuration, simply controlling the voltage difference between the positive and negative terminals of the LED slightly higher than its forward voltage will easily light up the LED. If the voltage difference is too high, a series current-limiting resistor is often used to restrict the voltage and current flowing through the LED, preventing it from being damaged. For more information on designing a current-limiting resistor, you can refer to this article.
Common Anode configuration
In the common anode configuration, multiple LEDs configured in direct configuration are connected together by their anodes. Taking the circuit diagram of OPS-S4010SE-GW as an example, the circuit diagram shows that the anodes of eight LEDs labeled A-G, Dp are connected together, while the cathodes of the LEDs are connected to the output PINs. The illumination method of the common anode configuration is the same as the direct configuration, where the LEDs can be lit up by applying the correct voltage across their terminals. If the voltage difference between the positive and negative terminals of the LED is too high, a series current-limiting resistor is often used to restrict the voltage and current flowing through the LED, allowing the LED to be illuminated using a higher voltage without being damaged. The diagram below illustrates a LED circuit that includes the common anode configuration. For designing a current-limiting resistor, you can refer to this article. The order of the resistor and LED can be interchanged; both configurations can light up the LED.
Common Cathode configuration
The common cathode configuration of LEDs involves connecting the cathodes of multiple LEDs, which are configured in direct configuration, together. Taking the circuit diagram of OPS-S4011SE-GW as an example, the circuit diagram shows that the cathodes of eight LEDs labeled A-G, Dp are connected together, while the anodes of the LEDs are connected to the output PINs. The illumination method of the common cathode configuration is the same as the direct configuration, where the LEDs can be lit up by applying the correct voltage across their terminals. If the voltage difference between the positive and negative terminals of the LED is too high, a series current-limiting resistor is also used in this configuration to restrict the voltage and current flowing through the LED, allowing the LED to be illuminated using a higher voltage without being damaged. The diagram below illustrates a LED circuit that includes the common cathode configuration. For designing a current-limiting resistor, you can refer to this article. The order of the resistor and LED can be interchanged; both configurations can light up the LED.
Why are there fixed LED connection methods?
The main reasons are:
- To reduce the number of connections between the module and external circuitry.
- To enable individual illumination of each LED in different areas.
Let’s take the common anode configuration of a seven-segment display as an example. If direct wiring is used, the number of external pins would increase from PIN 10 to PIN 16. These additional pins would result in wasted PCB and module space. By using the common anode configuration, each LED can be individually lit up using the direct illumination method. This is why LED products commonly employ common cathode or common anode configurations.
Conclusion
The direct configuration allows for simple illumination of a single LED. However, if a product has multiple LEDs, using the common anode configuration and common cathode configuration can simultaneously reduce the number of output pins and enable individual illumination of each LED using the direct configuration method. Leap Opto is a professional manufacturer of LED seven-segment displays with 10+ years of experience. We can produce standard SMD LED 7-segment displays and THT LED 7-segment displays in both common anode and common cathode configurations. Our product range also includes standard SMD LED dot matrix displays, THT LED dot matrix displays, and custom-made SMD & THT LED displays. If you have any related requirements, please contact us at Sales@opledtw.com or through our contact form.