Active or Passive Cooling: What’s Best For The CmRat?

Active Passive Cooling CmRat

When discussing cooling solutions for devices like the CmRat, the terms “active” and “passive” cooling refer to two different approaches to dissipating heat generated by components such the compute module and the NVMe. Proper cooling ensures that devices run smoothly, perform optimally, and avoid overheating, which can lead to reduced lifespan or hardware failures.

Active Cooling

Active cooling uses mechanical components to actively reduce the temperature of a device. The most common form of active cooling involves fans or liquid cooling systems.

How it works: Active cooling systems typically consist of fans, heat pipes, or liquid-based systems that move air or fluid over hot components to transfer heat away from them. In the case of the CmRat, an active cooling setup might include a fan mounted on a heatsink attached to the processor or other high-heat components.

Advantages:

  • More effective at cooling: Active systems are generally better at lowering temperatures, making them ideal for high-performance tasks that generate a lot of heat, like running server applications, heavy computing, or gaming.
  • Improved longevity: By keeping components cooler under heavy loads, active cooling helps extend the lifespan of sensitive electronics.
  • Higher performance ceiling: Devices using active cooling can often perform at higher levels without throttling due to heat.

Disadvantages:

  • Power consumption: Active cooling systems use energy, which may slightly reduce the overall efficiency of the device.
  • Noise: Fans and other mechanical components can generate noise, which may be undesirable in certain settings, especially if the goal is to maintain a silent operation.
  • Maintenance: Fans and moving parts require periodic cleaning or replacement to ensure optimal performance.

Active Cooling On The CmRat

The stock CmRat comes equipped with a CM4-FAN-3007-B-12V, a 12V PWM fan running at 8000 RPM. It’s a fan that I have a love-hate relationship with. On one hand, I love it for its exceptional cooling performance, consistently keeping temperatures below 40°C. On the other hand, I hate it because, as of now, there’s no way to lower the fan’s RPM, making the noise quite bothersome.

You can find this fan on Aliexpress for around 15 bucks.

During our CasaOS testing, the temperature consistently stayed remarkably low. If the noise it’s not a problem for you, it’s definitely an excellent stock fan that can help extend the lifespan of your CmRat.

Better Active Cooling On The CmRat

User mnegon came up with a solution for active cooling by purchasing the Edatec CM4COOLER-S CM4 Heat Sink in silver and attaching a Geekpi “Pi Fan” (model GF4010S, 5V, 0.1A) on top.

The Edatec heatsink has a high profile, with its edges carefully filed down to ensure a flat bottom for easy installation. Simply attach it to your compute module using 4 screws, apply the thermal tape to the compute module, and secure it with the included nuts and standoffs.

You can place the GeekPi RGB fan on top to cool the entire unit.

To set it up, connect the red cable to +3V and the black cable to GND. The result is both visually appealing and provides even lower temperatures than the stock fan. And most importantly, the fan is very quiet so it’s ideal to use it in your home.

I’ll share more details in the future, as I still need to test this setup myself. But surely, for just under $15, you’ll achieve outstanding results.

Passive Cooling

Passive cooling, on the other hand, relies on natural heat dissipation without the use of moving parts or additional energy consumption. This is typically achieved by using materials with high thermal conductivity like aluminum or copper to absorb and radiate heat away from the components.

To be effective, passive cooling systems often require larger heatsinks or more surface area, which can take up more space inside a device or enclosure.

How it works: A passive cooling system typically uses a heatsink, which is a metal structure designed to maximize surface area, allowing heat to dissipate into the surrounding air. In the CmRat, a passive cooling solution might involve a large heatsink on the processor, helping to radiate heat without the need for fans.

Advantages:

  • Silent operation: Passive cooling is completely silent since there are no moving parts. This makes it ideal for applications where quiet operation is important, such as home servers or media centers.
  • No power consumption: Unlike active cooling, passive systems do not draw additional power, which can be beneficial for efficiency-focused setups like low-energy servers.
  • Low maintenance: With no mechanical parts to wear out or collect dust, passive cooling systems are often more reliable over long periods and require minimal upkeep.

Disadvantages:

  • Less effective cooling: Passive systems are generally less efficient at removing heat compared to active systems. In high-performance setups or under heavy loads, passive cooling may struggle to keep temperatures in check, potentially leading to thermal throttling or overheating.

Passive Cooling On The CmRat

DTV Electronics hasn’t officially approved any specific passive cooler, as users are free to experiment with different options. However, one of the best and most affordable choices to start with is the Waveshare 19623 CM4-HEATSINK, an aluminum heatsink designed specifically for the Raspberry Pi Compute Module 4 (CM4), with a notch for the antenna. It has a low profile and is easy to install—just attach it to your compute module using 4 screws, apply the thermal tape to the compute module, and secure it with the provided nuts and standoffs.

You can find it on Aliexpress for less than 5-6 euro.

The temperatures aren’t ideal, but I didn’t encounter any issues running everything even at over 70°C. However, prolonged exposure to such high temps may shorten the lifespan of your CmRat, so it’s important to use this heatsink with caution.

Bottom Line

When selecting a cooling solution for your CmRat, both active and passive cooling options have their merits, depending on your specific needs and environment. Active cooling, with its superior heat dissipation, is ideal for performance-driven tasks and environments where higher temperatures are a concern. The stock fan, while noisy, performs well under load, and there are affordable upgrades like the combination of the Edatec heatsink and GeekPi fan that can offer even better cooling performance.

On the other hand, passive cooling provides a noise-free and low-maintenance alternative, making it suitable for quieter applications like home servers or media centers. Although less effective at cooling during heavy loads, it’s still a viable option for users who prioritize silence and simplicity, as seen with the Waveshare CM4-HEATSINK.

Moreover, as demonstrated by user mnegon, you can also mix and match components to create a hybrid solution that takes advantage of the strengths of both active and passive cooling (and the RGB-coolness). By carefully selecting heatsinks and fans, you can achieve optimal thermal performance while minimizing noise and power consumption.

Ultimately, the choice between active and passive cooling comes down to balancing performance, noise, power consumption, and maintenance. Whether you prefer a more powerful active cooling setup, a quieter, hands-off passive solution, or a custom hybrid approach, all options can help ensure your CmRat operates smoothly and remains protected from overheating, extending its lifespan and performance capabilities.

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