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ESC poltergeist?

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Old 02-23-2007, 10:06 PM
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wsmalley
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Default ESC poltergeist?

Well guys I decided to jump into the 20th Century and go Brushless! Got a new CC Phoenix 60, with an Aveox 36/24/2 hooked to a WeMoTec Midi fan. Haven't been able to get into the ESC programming mode yet. After running it a few minutes, I turned the throttle off on my Futaba 8UAF, then, I turned the Tx off. I was reaching to unplug the battery pack when the motor cranked up and ran a couple of seconds and shut off, a few seconds later-same thing, and again...... Unplugged the battery. Why is the motor starting? Would hate to have my hands around that thing if it had a prop, instead of a fan! What's going on? And, how come these new ESC's don't have an on/off switch? My old brushed controllers had a switch, and one or two had an arming button. Or, am I missing something?
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Old 02-23-2007, 11:02 PM
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Default RE: ESC poltergeist?

When the receiver is powered but the transmitter is off, the receiver will often generate random signals. It's not so bad if this merely causes a servo to twitch, but it can just as easily send unwanted signals to the ESC, which can be quite dangerous when it unexpectedly powers up the motor.

For this reason, always, always, always disconnect the battery pack BEFORE turning off the transmitter. Likewise, never plug in the battery pack until the transmitter is turned on. The transmitter should always be turned on first and turned off last. This applies to both brushed and brushless electric power systems and is the most basic rule of electronic flight safety.

- Jeff
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Old 02-24-2007, 10:31 AM
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Default RE: ESC poltergeist?

Good info! A feature everyone should understand. My old stuff had an on/off switch on the controller, and in some cases an arming switch. With these newer designs, one has to think about designing the craft for easy access to disconnect the battery between flights. I'm not sure I understand why a switch is not incorporated into the design. With these high powered motors today, seems like the margin for error is much greater!
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Old 02-24-2007, 05:46 PM
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Default RE: ESC poltergeist?

To safely and completely remove power to an electric aircraft, you need to interrupt the connection between the battery and the ESC. Whatever device you use to make and break that connection must carry the full current of the power system. For today's high powered systems, a switch would have to be a pretty large one, plus it introduces another failure point and more weight.

A few ESCs do have a switch, but its only function is to isolate the ESC from the receiver. It does not cut off power to the ESC, so it does not positively prevent inadvertent motor start-up. The safety and effectiveness of ESC switches has been debated a great deal. [link=http://www.rcgroups.com/forums/showthread.php?t=446961]Click here for one thread on the topic.[/link]

In addition, the ESC still draws a small amount of power even when its switch is "off." Over time, it will drain the battery if you leave it connected. Many folks have ruined lipos by leaving them connected to ESCs that are "off." Of course, for safety reasons, you should not leave lipos in a plane after flying anyway, and you definitely should not charge a lipo that is buried in a plane!

Some folks use a heavy-duty harness inline with a battery lead that requires plugging in a heavy-duty jumper (often made from a Deans Ultra plug) to complete the circuit. The plug is located such that it is accessible from outside the plane.

- Jeff
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Old 02-24-2007, 06:52 PM
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Default RE: ESC poltergeist?

I suppose you guys are goin' to tell me next that the North won the Civil War! Well, I'll bet someone else learned something here today. Sorry, to raise an old, much discussed issue, but there are new folks going into electric, high powered stuff everyday. Looks like EDF's may be the new wave.
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Old 03-01-2007, 11:02 AM
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Default RE: ESC poltergeist?


ORIGINAL: jdetray

To safely and completely remove power to an electric aircraft, you need to interrupt the connection between the battery and the ESC. Whatever device you use to make and break that connection must carry the full current of the power system. For today's high powered systems, a switch would have to be a pretty large one, plus it introduces another failure point and more weight.

- Jeff
The switch only has to CARRY the maximum current required by the system, not actually SWITCH currents at this level - unless you try to shut the plane off when running at full throttle. A DPST switch rated at 5 amps is more than adequate in applications where you are using a 40 amp ESC. Wire both poles in parallel. These switches come an a fairly small format, measureing less than 1/2 inch cube, including solder terminals and mounting through a 1/4" diameter hole.

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Old 03-01-2007, 11:42 AM
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Default RE: ESC poltergeist?

Hi Red -

My concern is that people view the switch as a safety device. As such, if they have a motor that unexpectedly starts up, flipping off the switch may be the first thing they think of doing. Since the switch will at that moment be carrying the full motor current, what would the result be?

- Jeff
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