Quieting a Loud Projector Fan: A Detailed Guide to Heatsink and Fan Optimization

GreatScott!

Summary:

This video details the process of reducing the loud fan noise of a 200€ projector.

• The speaker identifies the primary issue as the cooling fan, which operates at over 50dBA.
• A teardown reveals a compact, well-designed interior and a 50W high-power LED cooled by a heatsink system.
• Initial analysis shows that the LED itself cannot be easily replaced due to optics.
• The cooling system consists of a passive heatsink with heat pipes and an active fan.
• Replacing the projector's original thermal paste with a higher-quality one reduced the LED heatsink temperature by 1°C.
• Testing various replacement fans, the speaker finds one that reduces noise by 10dBA but increases temperature by 5°C, deemed acceptable.
• A second, hidden centrifugal fan for the optics is discovered, which becomes the new loudest component.
• Since a quieter replacement for the second fan isn't available, a 9V regulator is installed to slow down the original fan, slightly reducing its noise.
• The final result is a significant noise reduction from approximately 53dBA to 46.4dBA, with the projector passing a 2-hour stress test.

My Projector Problem! [0:00]

The video begins by highlighting the increased affordability of projectors, particularly a 200€ model acquired from AliExpress that offers good image quality and user interface. The primary issue identified is the projector's loud cooling fan, measured at over 50dBA, comparable to an electric toothbrush. The goal is to make the fan quieter while maintaining functionality.

Teardown of the Projector [2:30]

The speaker disassembles the projector by removing hidden screws, detaching the front plastic piece, and carefully cracking open the shell. This reveals a neatly organized internal structure with a main PCB and well-managed wiring, indicating a thoughtful design. The projector is briefly powered on after partial disassembly to confirm all components are still functional.

Loud Fan Noise? [3:30]

The source of the loud fan noise is quickly identified, located behind a heatsink. After removing additional screws, the heatsink is pulled out, exposing a powerful fan cooling a high-power LED. This LED is intensely bright and significantly heats the surrounding air and itself. The speaker notes the necessity of understanding the heatsink system to effectively reduce fan noise by either producing less heat or dissipating it more efficiently.

LED Change? [4:19]

The high-power LED's part number is unidentifiable through online searches. Measuring its voltage and current suggests it is a 50W LED. A comparison with a common 50W LED reveals the projector's LED is significantly smaller, making heat dissipation more challenging for the same power loss. Replacing the LED is deemed impractical due to its specialized optics designed for its specific size.

• LED Power Estimation [0:04:34]
  • Voltage and current measurements (24.3V * 2.23A = 55.5W) suggest it's approximately a 50W high-power LED.

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• Size Discrepancy and Heat Dissipation [0:04:45]
  • The projector's LED is much smaller than typical 50W LEDs.
  • A smaller surface area makes it harder to dissipate heat quickly, requiring more aggressive cooling.

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• Optics and Replacement Feasibility [0:05:03]
  • The projector's optics are custom-designed for the small LED size, making a replacement with a larger, easier-to-cool LED impossible without redesigning the optical path.

Passive Heatsink! [5:15]

The main heatsink consists of the LED's aluminum PCB attached to a thicker aluminum piece, featuring two heat pipes leading to metal fins. This upper part functions as a passive heatsink.

• Passive Heatsink Principle [0:05:33]
  • A large metal slab dissipates heat through convection without active components like fans.
• Limitations of Small Passive Heatsinks [0:05:53]
  • When reduced to the projector's heatsink size, passive cooling is insufficient, leading to LED temperatures around 200°C.
• Projector's Thermal Management [0:06:09]
  • The projector's LED temperature is actively monitored, and an emergency thermal switch opens at 80°C to prevent overheating.

Active Heatsink! [6:22]

The projector's cooling system is an active one, using heat pipes to transfer heat from the LED to the fins, where a fan blows air to dissipate it.

• Components of Active Cooling [0:06:21]
  • Heat pipes efficiently move heat to the fin array.
  • A fan actively forces air through the fins, enhancing heat transfer.

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• Space Constraints [0:06:41]
  • Increasing the size of the heatsink is not possible due to the projector's compact housing and custom-made components.

Thermal Paste Replacement? [6:55]

The connection between the LED PCB and the aluminum heatsink uses thermal paste. The original paste appeared dry and insufficient.

• Hypothesis for Improvement [0:07:05]
  • Replacing the old thermal paste with a better quality one could improve thermal conductivity, moving heat more quickly from the LED to the heatsink.
• Temperature Test (Before) [0:07:18]
  • A 10-minute test with the old thermal paste showed the upper heatsink at approximately 46.5°C and the lower heatsink at 40.5°C.

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• Thermal Paste Application [0:07:36]
  • The old paste was removed, and new thermal paste was applied.
• Temperature Test (After) [0:07:36]
  • Repeating the test with new thermal paste showed the LED heatsink temperature decreased by 1°C, from 46.5°C to 45.5°C, a modest but positive improvement.

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Fan Replacement? [7:51]

Further analysis with a thermal camera showed the outer fins of the heatsink had room for more heat, suggesting a fan with less airflow but quieter operation might suffice.

• Original Fan Specifications [0:08:08]
  • The original fan spins at 3000 RPM, producing an airflow of 40.25 CFM and a noise level of 32.5 dBA according to its datasheet.
  • The cooling capability is primarily dependent on airflow.

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• Replacement Fan Selection [0:08:41]
  • Three new fans with similar dimensions but lower airflow and significantly lower dBA (22, 21, and 16 dBA respectively) were acquired for testing.
  • A 10 dBA drop is perceived as half the loudness.
• Testing New Fans [0:09:01]
  • The old system produced around 60 dBA at the heatsink and reached a maximum temperature of 47°C after 20 minutes.
  • Each new fan was installed and tested, measuring both dBA and temperature.
  • All tested fans achieved approximately a 10 dBA drop in noise.
  • Fan 1 was chosen as the winner, reducing noise to 50 dBA with a temperature increase to 52°C (a 5°C increase from the original 47°C). This temperature increase was considered acceptable.

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Surprise (2nd) Fan?! [9:47]

During testing with the quieter primary fan, the projector was still noticeably loud, leading to the discovery of a second, hidden centrifugal fan responsible for cooling the optics chamber.

• Identification of Second Fan [0:09:52]
  • This fan became the loudest component after the primary fan was quieted.

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• Challenges with Replacement [0:10:27]
  • The selection of suitable replacement centrifugal fans was very limited.
  • The only available option was louder than the original fan.
• Speed Reduction Solution [0:10:39]
  • An attempt to adjust the original fan's speed via its yellow wire revealed it only measured RPM.
  • The solution involved cutting the fan's power wires and installing a 9V regulator to reduce the 12V supply to 9V, slowing down the fan and slightly reducing its noise.

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Final Test & Verdict [11:11]

After reassembling the projector with the quieter primary fan and the voltage-regulated secondary fan, a 2-hour stress test was performed, which the projector survived without any issues.

• Before and After Noise Comparison [0:11:22]
  • The noise level before modifications was approximately 53 dBA.
  • After the modifications, the noise level was reduced to approximately 46.4 dBA.

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• Considerations [0:11:38]
  • The speaker emphasizes that increasing operating temperatures, even slightly, can potentially reduce the lifetime of electronic components. The chosen 5°C increase was deemed acceptable but is a trade-off.