LED Receiving Cards – Choosing for Your Screen

LED receiving cards are a component you cannot see from the front of the screen, yet they determine whether the modules display the image sharply, stably and in line with the video processor's parameters. In an advertising installation, an LED wall in a club, a screen in a shopping centre or a mobile event structure, the receiving card is responsible for passing data to the right sections of the screen. A wrong choice can mean refresh-rate problems, incorrect colours, limited resolution or difficult servicing.

What are LED receiving cards?

An LED receiving card, also called a receiving card, is mounted inside a module, a cabinet or another structural part of the screen. It receives the signal sent from the controller or video processor and then drives a specific number of LED pixels. In practice, the card determines which diodes light up, at what brightness and at which moment of the refresh cycle.

In a typical system the signal runs from the image source, for example a computer, a media player or a camera, to the video processor. The processor scales and splits the image and then sends the data over network cable to the receiving cards. Each card drives its assigned portion of the LED surface. Subsequent cards pass the data on, forming a signal chain for the whole screen.

A receiving card should not be confused with a sending card. The sending card or the processor's output port passes data to the installation, while the receiving card handles control on the side of the LED modules. In small screens both tasks may be integrated in a single control device, but in professional LED walls they are usually separate components of the system.

Choosing a card for the screen's resolution and configuration

The most important parameter is the maximum number of pixels the card can handle. This is not only about the total resolution of the screen. What also counts is how the surface is divided into sections assigned to particular cards, and the limits on the width and height of the image handled by a single output.

For example, a screen with a resolution of 1920 × 1080 pixels may use several or even a dozen receiving cards. The split depends on the dimensions of the cabinets, the resolution of the modules used and the planned cable routing. A card with high pixel capacity is not always the best choice. In a fine-pitch screen it can simplify cabling, but you must at the same time keep a bandwidth reserve and the correct placement of cards inside the structure.

Before choosing, it is worth establishing three data points: the resolution of a single module, the number of modules in a cabinet and the target resolution of the whole wall. Only then can you plan how many cards are needed and how to split the load. This stage matters both for fixed screens and for rental structures, which must be quick to configure in different layouts.

Module scanning and hardware compatibility

The receiving card must work with the type of drive used in the LED module. Key factors include the scanning parameters, the type of LED driver ICs and the HUB configuration, that is, the connector linking the card to the modules. Not every card will work correctly with every module, even if they can be physically connected.

An incorrect scanning configuration can cause flickering, missing parts of the image, disturbances in rows or incorrect brightness. For this reason, when building a screen from components you should use the configuration file supplied for the given module. The file stores parameters such as pixel layout, colour channel order, scan frequency and driver settings.

Particular care is needed when upgrading an existing wall. Replacing cards with a different model may require not only loading a configuration but also updating the video processor or changing the connection topology. The installation may work but fail to reach its original image quality if the system is not properly calibrated.

Refresh rate, greyscale and picture for the camera

The receiving card affects parameters that are especially noticeable in professional applications. One of them is the refresh rate. For screens viewed only up close by shop customers or venue guests, standard values are often sufficient. The situation changes when the screen works in front of a camera, during an event streamed online or on a television stage.

Too low a refresh rate can show up as banding, flicker or an uneven picture in the recording. For such productions it is worth designing the system with cards and modules that support a higher refresh rate and correct control at low brightness. The card alone will not fix the module's limitations, but it can be the limiting factor for the capabilities of the whole set.

Greyscale is also important, that is, the number of intermediate levels between black and full brightness. Good reproduction of tonal transitions matters for video material, product photos and animations with gradients. In a shop window, imperfections may be less visible than on a large LED wall viewed from a short distance. The choice of parameters should therefore follow from the screen's purpose, not only from the price of the component.

Connections, redundancy and service

Receiving cards most often communicate via standard network cables. The order of connections must match the configuration in the control software. A badly routed chain will not always switch the screen off completely – sometimes it shows up as swapped parts of the image, no signal in some of the cabinets or the wrong orientation of sections.

In larger screens it is worth considering signal redundancy. It consists of a backup data path that takes over after the primary connection is interrupted. Such a solution is justified in advertising displays that run unattended for long periods, information screens in commercial venues and installations where downtime carries a high operating cost.

When planning service, access to the cards counts. In a front-service screen the card should be replaceable from the front together with the module or through a suitable service opening. In a rear-access structure, space behind the screen must be provided. A good design also includes cable labelling and port marking, because with several dozen cabinets this cuts diagnosis from hours to minutes.

How to choose a control system for the application

For a small lightbox, a simple text display or a screen in a shop window, ease of configuration and compatibility with a specific module are often the priority. For an LED wall in a conference room, image scaling, support for multiple sources and stable refresh become more important. Event screens additionally require quick installation, robust connections and the ability to work in changing configurations.

The working environment should also be taken into account. An outdoor screen exposed to high brightness and long operation will have different requirements than an indoor screen in a showroom. In a transparent or flexible installation, structural limitations may force a particular placement of cards and cables. Control components should be chosen together with the modules, power supply, processor and structure, not as an independent purchase.

In projects based on LED modules, LEDMAX EUROPE can help match the receiving card, processor and other control elements to the real resolution and application of the screen. The best starting point is always the specification of the modules and a drawing of the planned surface. This way the system has the right performance reserve from the start, and later commissioning does not turn into a series of random configuration attempts.