304 North Cardinal St.
Dorchester Center, MA 02124
304 North Cardinal St.
Dorchester Center, MA 02124
On the left are a series of power measurements I made on the Celluon PicoPro projector with an optical engine designed by Sony using a Microvision scanning mirror. The power was calculated based on the voltage and current from current coming from the battery using the HDMI input.
The first 6 measurements were with a solid image of the black/white/color indicated. For the last 3 measurements I did an image that was half black on the left and the other half white, an image that was top half black, and a screen of 1 pixel wide vertical stripes. The reason for the various colors/patterns was to gain some additional insight into the power consumption (and will be covered in a future article). In addition to the power (in Watts) added a column with the delta power from the Black image.
The Celluon PicoPro consumes 2.57 Watts for a fully black image (there are color lines at the bottom, presumably for laser brightness calibration) and 6.14W for a 32 lumen full white image. When you consider that a smart phone running with the GPS only consumes about 2.5W and a smart phone LCD on full brightness consumes about 1W to 1.5W, over 6W is a lot of power (Displaymate has and excellent article on smartphone displays that includes the power consumption). The Celluon has a 3260mah / 12.3Wh battery which is bigger than what goes in even large smartphones (and fills most of the left side of the case).
So why does the Celluon unit not need a fan, the answer is A) it only outputs 32-lumens and B) it use a lot of thermal management build into the case to spread the heat from the projector. In the picture below I have shown some of the key aspects of the thermal management. I have flipped over the projector and indicated with dashed rectangles were the thermal pads (a light blue color) go to the projector unit. In addition the cast aluminum body used to hold the lasers and the optics which acts as a heat sink to spread the heat, there is gray flexible heat spreading material lining the entire top and bottom of the case plus a more hidden, a heat sink amalgamation essentially dedicated to the lasers as well as aluminum fins around the sides of the case.
The heat spreading material on the left (as view) top of the case is pretty much dedicated to the battery, but all the rest of the heat spreading, particularly along the bottom of the case goes to the projector.
The most interesting feature is that there is a dedicated heat path from the area where the lasers are held in the cast body to the a heat sink “hidden chamber” or what I have nicknamed “the thermal corset”. You should notice that there are three (3) light blue heat pads on the right side of the case top and that the middle one is isolated from the other two. This middle one is also thicker and goes through a hole in the main case body to a chamber that filled with a heat sink material and then covered with an outer case. This also explains why the Cellouon unit looks like it is in two parts from the outside.
Don’t get me wrong, having a fanless projector is desirable, but it is not due to the “magic” of using lasers. Quite to the contrary, the Celluon unit has comparitively poor lumens per Watt, about double the power of what a similar DLP projector would take for the same lumens.
You may want to notice in the table that if you add up the “delta” red, green, and blue it totals to a lot more than the delta white. The reason for this is that the Celluon unit never puts out “pure” fully saturated primary colors. It always mixes a significant amount of the other two colors (I have verified this with several methods including using color filters over the output and using a spectral-meter). This has to be done (and is done with LED projectors as well) so that the colors called for by standard movies and pictures are not over-saturated (if you don’t do this, green grass, for example” will look like it is glowing).
Another interesting result is that the device consumes more power if I put up a pattern were the left half is black and the right half is white rather than having the top half black and the bottom half white. This probably has something to do with laser heating and not getting a chance to cool down between lines.
I also put up a pattern with alternating 1 pixel wide vertical lines and it should be noted that the power is between that of the left/right half screen image and the full white image.
So what does this mean in actual use? With “typical” movie content, the image is typically about 25% to 33% (depends on the movie) of full white so the projector will be consuming about 4 Watts per hour which with a 12.3Wh battery will go about 3 hours. But if you are web browsing, the content is often more like 90% of full white so it will be consuming over 6W per hour or 4 to 6 times what a typical smartphone displays consumes. Note this is before you add in the power consumed in getting and processing the data (say from the internet).
The Celluon projector may be fanless, but not because it is efficient. From a product perspective, it does do a good job with its “thermal corset” of hiding/managing the power.
This study works from the “top down” by measuring the power and seeing where the heat is going in the case, the next time I plan to work some “bottom’s up” numbers to help show what causes the high power consumption and how it might change in the future.