Posted by Tom Frank on the RC Forums
The JooVuu Case - how well does it control internal heat generation?
The answer to this question is..."
Very well, indeed!".
The bottom line is my tests showed the Mobius internal DSP/memory chip area maximum temperature and the external heat sink maximum temperature to be a few degrees less with the Mobius in the JooVuu case than when the Mobius is in the open air!
This may sound impossible to some, and took me by a bit of surprise, but the reality is that heat is transferred very efficiently from the Mobius heat sink plates by conduction (the most efficient method) to the much larger mass and surface area of the JooVuu case back end metal heat sink. And the JooVuu case can then more efficiently get rid of that heat than the Mobius can by radiation and convection (air movement) to the ambient air by virtue of the much large heat sink area. The net result is a very slight gain in overall heat transfer efficiency.
It's important to keep in mind the ambient air temperature will greatly impact the temperatures I posted below. On a hot summer day the air can easily be 30 deg. F higher than my indoor test room temperature (nominal 72 deg. F.) in many regions, and the camera temperatures will be proportionally higher. The same goes for cold winter temperature, when the camera battery starts to lose it's ability to hold voltage and deliver the current the camera needs to operate when the temperature drops below about 40 deg. F. So this means the JooVuu case is not likely to help keep the camera battery any warmer than the exposed Mobius can due to it very efficient heat sink design!
This conjures up the notion in my mind that perhaps the JooVuu case design could be improved with a new "hybrid" back end, comprised of a plastic piece of similar shape to the current one, but with one large (or perhaps two smaller)
removable finned aluminum heat sink(s) on top, attached with small machine screws like the tripod mount with a gasket like the back end to make it waterproof. In cold weather, the metal heat sink(s) could be removed and replaced with a simple plastic plate(s) to diminish the heat loss and give the Mobius a longer recording time in cold weather. It could save some weight in the process, and might even be able to float?
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For the more technically inclined, here's more detail on the testing:
I did a series of tests using digital temperature logging hardware with two thermal sensors. My tests were all indoor bench tests with ambient air temperature nominally about 72 deg. F.
In some tests, I also turned on cooling airflow supplied by a small 8 in. dia. "workstation" fan to simulate camera motion on a slow flying RC plane, or other action sport use.
In some tests I measure Mobius internal chip area temperature by removing the CMOS module and connecting it to an extension cable running out through the case lens opening, along with a thermal sensor placed adjacent to the DSP/memory chips inside the Mobius case. Lens openings in the case were taped shut to contain heat in the case to simulate normal use.
Here's a summary of the tests and temperatures measured. The time/temperature recording graphs are also attached for you perusal.
Test 1: Mobius DSP and Memory Chip Temp in open air (no Mobius case)
- DSP chip max. temp. = 107 deg. F.
- Memory chip max. temp = 99 deg. F.
Test 2: Mobius closed case Heat Sink Plate Temp
- Forward Heat Sink Plate max. temp. = 111 deg. F., reduced to stable 85 deg. F. with cooling airflow
- Aft Heat Sink Plate max. temp. = 114 deg. F., reduced to stable 88 deg. F. with cooling airflow
Test 3: Mobius Internal Chip Area and External Aft Heat Sink Temp
- Internal Chip Area max. temp. = 115 deg. F., reduced to stable 98 deg. F with cooling airflow
- External Aft Heat Sink max. temp. = 99 deg. F., reduced to stable 83 deg. F. with cooling airflow
Test 4: JooVuu Case Heat Sink Temp with Mobius Recording Inside
- Heat Sink Top max. temp. (sensor on "bubble" over Mobius heat sinks) = 96. deg. F., reduced to stable 83 deg. F. with cooling airflow
- Heat Sink Bottom max. temp. (sensor on bottom directly under top sensor) =96 deg. F., reduced to stable 83 deg. F. with cooling airflow
Test 5: JooVoo Case Heat Sink and Mobius Chip Area Internal Temp
- Mobius Internal Chip Area max. temp = 114 deg. F., reduced to stable 96 deg. F. with cooling airflow
- JooVuu Heat Sink Top max. temp = 95 deg. F., reduced to stable 78 deg. F. with cooling airflow