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Jan 30, 2008, 03:04 AM
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Jack Crossfire's Avatar
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More flaming BEC's 4 U

So metal gears arrived after only 2 days. Unfortunately, the same story from 1/20/08 happened. Clearly the metal gears needed more current and the LM7805 promptly heated over 200F once the servos started moving. Then it just shuts down and we lose servo authority. Another point in favor of the pilot on the 1/23 crash.

Now alternatives are $25 for a commercial BEC, plug it into the BL-35X ESC, get a separate battery, build a buck converter, or just write blogs about it. Remember what happened the last time we used an ESC for servo power.

According to this story the HS-65's need up to 1.3A so that's 6A, almost as much as a second rotor. At least Hillary's not flying it.

Ultimate BEC 4 U:

HS-65 metal weight: 10.1g
HS-65 karbonite weight: 9.3g

Should be noted our boss 2 bosses ago spent a year trying to get buck converters to work. They never did really work, and then he quit.
Last edited by Jack Crossfire; Jan 30, 2008 at 05:14 AM.
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Sep 10, 2008, 06:29 AM
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kbosak's Avatar
I think using switched BEC of your own design is asking for EMC trouble around your autopilot.
Try running 5A LM1084 from 2S lipo.
"The LM1084 is a series of low dropout voltage positive
regulators with a maximum dropout of 1.5V at 5A of load
current. It has the same pin-out as National Semiconductor’s
industry standard LM317."
Sep 10, 2008, 12:28 PM
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Jack Crossfire's Avatar
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The CC-BEC worked fine and had many hours of autopilot time. It only powered the servos. The sensors were all LM317 regulated.

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