Yesterday I took my new 3DR hexa outside for the first time. Weather was nice and sunny with brisk -7°c temperature. Even though everything worked well when testing, I immediately ran into problems outside. After connecting the battery all of the ESCs started beeping rapidly (two times per second) and refused to spin the motors. I took the hexa inside for a while to warm up for a while and the problem went away and everything seemed to work fine. Unfortunately as we all know, the assumption is the mother of all fuck ups.
I hovered the hexa, but each time I tried to land motors sped up suddenly and the whole thing flipped over faster than I could react. After breaking two props I started investigating further. There was a couple of helpful threads, one offering working solution to calibrate ESC at low temperature.
What I think what happened is this: Pwm value that ESC reads from APM changes a little with temperature. If we assume that lowest value in room temperature would be 1000, in -7 degrees it could be say 990. Now during calibration esc has saved value 1000 as the smallest possible value. When it reads value 990 at cold startup, it decides it’s not a valid value and refuses to start and starts to beep as a warning.
The real danger is in situation where ESC has started successfully, but the temperature goes down. At low throttle pwm value goes under the min limit and ESC turns off as a safety measure. Since not all ESCs do this at the same time, what happens during the flight is that APM tries to compensate this with other motors resulting an immediate flip.
Working solution seems to be to calibrate the ESCs at the lowest temperature you are going to fly. After doing that I had no problem flying outside. I think this would be important thing to mention in the wiki.
Comments
Hey guys - for anyone that has been looking what ESCs to buy for cold weather - choose these:
ZTW Spider Series 30A OPTO
Tested on my new build, no issues whatsoever. -20 Celsius? No problem! Work like a charm.
CorrosionX is a spray (liquid) that deposits a thin film on the surface you are spraying it on. Some people just dump their electronics in jar of that stuff and let ithe excess drip off afterwards. It protects metal against corrosion and is also a dielectric protecting electronics against short circuits. RC car guys use it to protect their ESC and RX. Some people even use it on servos --> https://www.youtube.com/watch?v=g2obApmI8vI
There are also other silimar products like Wet Protect that should also get the job done.
I think you can cover the whole APM, excluding the baro, without any problems.
ESCs are not more sensitive to moisture than other electronics. In your case snow/water got inside the ESC and shorted something. Anyway, if there's a possibility that your electronics might get wet then it's a good idea to coat them with something like CorrosionX.
Glad I read this before flying my quad, I am far from the maiden flight though.
Hi THomas, yes I use this method when level is only slightly off. But when it's completely screwd I just can't bring quad up into the air. And this is what usually happens after cold landing.
Max: there is a RC-controller method for leveling the vehicle:
http://code.google.com/p/arducopter/wiki/AC2_Flying#Field_Calibrations
I fly in up to -15C in Russia with Hobbywing ESCs and it's going OK. But I have another problem with cold on my APM 2.5 quadcopter. As soon as it goes below +5C leveling gets completely screwd-up upon each landing. Soft landing into snow or hard landing, regardless. So I have to connect to notebook and level again, which is annoying. It's not happening in warm weather. Something on IMU side which I don't understand...
I also fly my 3RD kit quad in Finland in as low as -20C. I have calibrated the ESCs indoors and always connect the battery before I take it out into the cold. I have logged about 1h of airtime (only stabilize, no auto) this winter without problems.
After the battery runs out and I switch it to a fresh one the motors beep rapidly as explained here so I take it indoors for a while and warm it up.
I flew my quadrocopter at about -10 C and it flew ok, but the battery alarm went off after about a minute, so I was assuming the battery didn't like the cold.
Dany, that's what I'm afraid of too. Couldn't you have a problem where they lose the signal as they warm up in flight?
-
1
-
2
-
3
of 3 Next