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Kinect teardown

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NiHaoMike:
Recently (several weeks ago), I got a Kinect to play with. One of its main downsides is that it needs its own power supply. I opened it up to see if I can make it powered from USB.
(Please look at http://openkinect.org/wiki/Main_Page for background information.)

You'll note that R4 is circled. That sets the UVLO for the 12V input, which is regulated down to 3.3V before anything uses it. The 3.3V buck regulator (a ST L6728) is capable of operating from 5V, but there's an external UVLO that prevents operation at that voltage. Simply add a 4.7k resistor in parallel with R4 and the Kinect will operate from a 5V supply. Current draw is about 700-800mA. A USB 3.0 port will power it, but since all of my PCs only have USB 2.0, that would require two USB connections for reliable operation. I left it running from 5V for a few hours and nothing is getting warmer than when it's running from 12V. Just to be safe, however, I rewired the fan to an always on 5V line. (That will decrease operating temperatures, prolonging lifetime and reducing sensor noise.)

Some interesting observations:
* There is a thermal fuse mounted to the IR projector. I'm guessing the developers had one melt down and decided to add the fuse just to be safe. It also looks like it was added after the sensor board was designed since it isn't directly connected to the sensor board as might be expected.
* There's a processor on the sensor board for video processing and a seemingly more powerful processor for audio processing. Why they would need such a powerful processor for audio is something I'm not understanding.
* The TI USB controller is actually for the auto leveling motor and accelerometer, despite it being labeled as an audio controller. I'm not sure why they didn't just use a generic USB microcontroller or a few GPIOs on the audio processor.

mikeselectricstuff:

--- Quote from: NiHaoMike on October 02, 2011, 10:37:33 pm ---I left it running from 5V for a few hours and nothing is getting warmer than when it's running from 12V.

--- End quote ---
Unless the audio processor is doing something, it never gets hot enough for the fan to start.

--- Quote ---Some interesting observations:
* There is a thermal fuse mounted to the IR projector. I'm guessing the developers had one melt down and decided to add the fuse just to be safe. It also looks like it was added after the sensor board was designed since it isn't directly connected to the sensor board as might be expected.

--- End quote ---
The Peltier under the laser actually heats it at room temp, so maybe to trip if the temperature feedback is lost

--- Quote ---* There's a processor on the sensor board for video processing and a seemingly more powerful processor for audio processing. Why they would need such a powerful processor for audio is something I'm not understanding.

--- End quote ---
Because it has several microphones, and does lots of clever processing to detect where the sound is coming from. ISTR it's a very meaty ARM running at several hundred MHz

Asus do a similar device without the audio and motor, whic is USB powered : http://www.asus.com/Multimedia/Motion_Sensor/Xtion_PRO/

It is also possible to run just the front sensor board on its own - ISTR it needs 5V and 3.3V, although I think the peltier module still takes the power draw over the 500mA USB limit. 
Unfortunately I think last time I looked the connector was unobtainable in small quantites.

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