COB LED Basics: A Beginner's Guide

After reviewing my previous posts, I realized that I had overlooked an important topic for those who are entirely new to the COB LED lighting world. This guide aims to provide a fundamental overview of COB LED lighting systems, making it an excellent starting point if you wish to transition from traditional lighting or are a beginner in indoor gardening.

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The components of COB LED systems are relatively straightforward. They consist of several parts that integrate seamlessly. Here are the main components of a COB LED system:

• The COB LEDs
• Heat sinks to which the COBs are mounted
• LED drivers supplying power to the COBs
• Wires connecting the COBs and drivers.

Pretty simple, right? Let’s explore further.

1. COB LEDs

The most crucial part of a COB LED lighting system is undoubtedly the COB LEDs themselves. "COB" stands for "Chip On Board," indicating that multiple LED chips are collectively mounted on a single substrate, which is typically ceramic or metal. LEDs function as semiconductors that emit photons when electrons flow through a junction and fill “electron holes” on the opposite side.

Manufacturers send out data sheets containing each unit’s specifications that determine the minimum, typical, and maximum values for various parameters. Here’s a link to a sample data sheet from Cree for the CXB. You can find several characteristics of a COB in the data sheet, including:

• Color temperature (Is the light warm or cool?)
• Typical forward voltage (What is the voltage across the COB at a certain current level?)
• Maximum current (How many amps can the LED handle before it fails?)
• Temperature (How does the maximum current rating change concerning the COB's temperature?)
• Luminous Flux (How bright is the light at a specific current and temperature?)
• Relative Spectral Distribution (What light wavelengths are most prominent in the COB's output? Does it peak in the blue or red spectrum?)

So, how are these chips fixed in place? While you can secure them with screws if the board has screw holes, using holders is typically the better option.

COB Holders

If soldering isn’t your thing or you lack an iron, you’re in luck. Many COBs come with compatible holders that not only mount the COB to the heat sink but also provide a push-in connection for wiring. These holders fit over the COB, screwing down into the heat sink, which securely affixes the COB against it. Once secured, wiring becomes straightforward; simply push it into the holder’s terminals, which press onto the COB's contact points. Easy peasy!

Reflectors

If you want to intensify your lighting, consider adding reflectors at the COB’s front (often requiring a separate adapter). Reflectors come in various angles, colors, and materials to meet your lighting needs. You can also attach glass lenses or diffusers to safeguard the COBs against dirt, moisture, and other garden debris.

2. Heat Sinks

Though highly energy-efficient, high-powered COB LEDs can emit considerable heat. If this heat isn’t managed, it can impact the COB's performance and possibly lead to damages; thus, effective heat removal is essential. Heat sinks are uniquely designed to withdraw this heat from the COBs, maintaining a cooler operating temperature. They are typically made from aluminum, which conducts heat excellently.

Heat sinks come in various configurations, from the conventional "fin" design to more modern "pin-fin" models. The design of the fins—be they rectangular or pin-style—serves to maximize the heat sink's surface area, promoting effective heat transfer from the COB to the surrounding air.

Heat sinks can be categorized into two types: active and passive.

Active Heat Sinks

Active heat sinks utilize fans to direct airflow over the fins to aid in heat dissipation. Employing an actively cooled heat sink allows for utilizing a more compact design than what is possible with passive options. However, should the fan's power supply fail, the heat sink may no longer cool the COB adequately.

Passive Heat Sinks

Passive heat sinks rely solely on metallic materials without any additional components. As a rule, passive heat sinks must be more substantial compared to their active peers to manage equivalent levels of heat. The beneficial aspect of passive heat sinks is they do not feature moving parts, eliminating the risk of a fan failure leading to overheating.

Thermal Interface

For effective contact between the COB and heat sink, it’s crucial to use a thermal interface such as thermal paste or pads. Mounting a COB directly onto the heat sink without any intermediary would lead to inefficient heat transfer, causing localized overheating.

3. LED Drivers

LED drivers act as transformers, converting AC power from your outlet into the DC power that COBs require. It's essential to ensure appropriate voltage and current specifications when selecting a driver. LED drivers often arrive unterminated, necessitating proper wiring connections to integrate with your system.

When shopping for an LED driver, ensure it can provide sufficient wattage to operate all COBs in your array while matching the necessary current and voltage. The two common types of LED drivers are: constant voltage drivers, which maintain a steady voltage, and constant current drivers, which stabilize current output. For newcomers to the realm of LEDs, constant current drivers are often easier to work with.

For a deeper understanding, it would be beneficial to read posts on matching drivers to LED COB specifications, the differences between wiring systems in series and parallel, and further insights into constant voltage versus constant current drivers.

4. Wiring

Wiring is the most accessible part of the assembly—most people have experience using wire. It’s critically important to use the right gauge to connect all your COBs back to the LED driver. It’s advisable to use 18-gauge solid core wire, but validating the specifics for your setting may yield better results.

And that wraps up the basics of a COB LED system! Always approach assembly with caution, as comprehension of electricity fundamentals can be incredibly helpful for safety. If electrical matters aren’t your strong suit, consider seeking assistance from a knowledgeable individual.

If you’re looking to explore in greater depth, the DIY Guides section is a treasure trove filled with builds, articles, and calculators to aid you in crafting your own LED grow lights.

For any inquiries, feel free to join our forum, where our community is more than willing to help you, regardless of your skill level.

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