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Custom GIANT multirotor - 25lbs payload, 20 minutes flight

#42
Just curious, did the TV station provide the white background screen?
No, we have our own cyclorama wall, which also happens to be the room where I do a lot of the assembly for larger projects. The crew just came in and told us where to put things.

I don't have a link to the interview yet because it's part of a special on wedding photography that's supposed to air October.
 
#43
Started soldering today. I've done about half of the 92 solder joints and 112 heatshrink coverings... I'm still waiting on my female bullets and 2 more ESCs, but hopefully I can start bench testing motor-esc pairs tomorrow
 
#44
Started soldering today. I've done about half of the 92 solder joints and 112 heatshrink coverings... I'm still waiting on my female bullets and 2 more ESCs, but hopefully I can start bench testing motor-esc pairs tomorrow
This is an incredible build so far. You know what would be awesome?? If you shipped it to me when you're done with it. That would be awesome.
 
#46
Sorry for the delay guys. I have been working on the X8... just not really stopping to post about it!

So far I've done all the soldering for the power system. Let's just say it was a lot.
IMG_1289.JPG IMG_1290.JPG IMG_1291.JPG

Then we bench tested all Motor-ESC pairs:
IMG_1293.JPG

Who needs cable management anyway?
IMG_1298.JPG IMG_1299.JPG

Assembly:
IMG_1301.JPG IMG_1302.JPG IMG_1305.JPG

Once we got everything set up with the Pixhawk, it was time for the inaugural arming. Powered up. Got the usual ESC beeps every second while the Pixhawk was initializing, then we armed the beast.

Except ESCs kept on beeping once every second. Indicating no signal.

Now, I know the ESCs and motors all work because I tested them using a Spektrum Receiver. And I know the Pixhawk works because I literally just had the same board installed in a quad. Even so, I decided to test the Pixhawk's PWM output with a servo. Everything seemed to work. Then I tested the motors again with a receiver. No issues there.

So what's going on here???? Why aren't my ESCs working with the PWM output from the Pixhawk???

My current theory is that the Pixhawk's 3.3v logic is simply not playing nicely with the T-Motor 80A HV Flame ESCs PWM input, so I've been trying to get a logic level shifter working. Does anyone have any other theories?
 
#48
How are you powering the Pixhawk? Do you have power to the servo rail?

Also have you gone through RC Calibration on the Pixhawk and "all at once" ESC calibration?
 
#49
Check out the Pixhawk schematic, sheet 9/12. Level shifters are on board, but both supplies are connected to 3.3V. I wonder what function those level shifters are intended to perform.

http://3drobotics.com/wp-content/uploads/2014/02/px4fmuv2.4.3_schematic.pdf

Have you put a tap in one of the servo connectors (a Y adapter will do) and scoped out the PWM signals in situ?
I remember reading that the Pixhawk was outputting 3.3v logic, but clearly that's not an issue for EVERY OTHER PWM DEVICE I'VE EVER TRIED. I don't have an Oscope here, but I'll try to test the max voltage with that Y-Harness.

How are you powering the Pixhawk? Do you have power to the servo rail?

Also have you gone through RC Calibration on the Pixhawk and "all at once" ESC calibration?
I've tried powering through the USB, the servo rail, and with the 3DR power module as well as with both the power module and the servo rail. Clearly it was working for the servo I plugged in, but the ESCs are having none of it. They are OPTO ESCs, so I'm guessing it doesn't really matter if I power the rail or not.

The all at once ESC calibration had no effect on the motors. They just keep doing that short beep once a second, indicating no signal.
 
#50
OK. I would need to study those ESC's to know if they are "really" opto-isolated. Sometimes it simply means "sans BEC", which is not at all the same. But if they are, it absolutely makes a difference if the servo rail is powered or not. The opto-isolated side cannot work without being powered, since it is 'isolated' from the motor control circuit!

So ideally you will have power via the power module port (I presume you are using an attopilot 180A, so this would be via BEC. I use Polulu 5V 2.5A) as well as to the rail (I use another Polulu 5V 2.5A regulator for redundancy).

If they are beeping repeatedly, I would go through Pixhawk ESC Calibration. First, go through RC Calibration. Then, unplug Pixhawk from USB or anything like that. Move your throttle to 100%, and plug it back in. Wait for the persistent blue/red blinking. Unplug Pixhawk, then plug it back in. Hold the safety button until you hear the tone. Then move throttle to 0. Unplug, and plug Pixhawk back in, and you should be able to arm as usual.

EDIT - I read that you tried the all-at-once. I'll think about what else it might be if you already tried that. What happens when you connect a servo tester to one of them?
 
#51
I've even tried using a logic level shifter to bump up the signal. I've got one of the sparkfun boards connected like this:
Screen Shot 2015-08-14 at 11.14.40 AM.png
Left side goes to Pixhawk output.
Right side goes to ESC input.
Orange goes to 3.3v.
Red goes to 5v.

I'll try it again with a powered servo rail and redo the all at once calibration.
 
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#52
yeah.. sounds like you're pretty deep down the rabbit hole. You really shouldn't need to do anything super fancy like that. High current or not, it's still just an ESC.

One thing to be aware of with higher end opto ESC's is they frequently are preconfigured from the factory to expect a certain PWM range. KDE for example assumes a Futaba-style 1100-1900us. So you might try checking the range Pixhawk is getting in RC Calibration to make sure it's in range, and if not, adjust your radio offsets to get it in that range.
 
#53
OK. I would need to study those ESC's to know if they are "really" opto-isolated. Sometimes it simply means "sans BEC", which is not at all the same. But if they are, it absolutely makes a difference if the servo rail is powered or not. The opto-isolated side cannot work without being powered, since it is 'isolated' from the motor control circuit!

So ideally you will have power via the power module port (I presume you are using an attopilot 180A, so this would be via BEC. I use Polulu 5V 2.5A) as well as to the rail (I use another Polulu 5V 2.5A regulator for redundancy).

If they are beeping repeatedly, I would go through Pixhawk ESC Calibration. First, go through RC Calibration. Then, unplug Pixhawk from USB or anything like that. Move your throttle to 100%, and plug it back in. Wait for the persistent blue/red blinking. Unplug Pixhawk, then plug it back in. Hold the safety button until you hear the tone. Then move throttle to 0. Unplug, and plug Pixhawk back in, and you should be able to arm as usual.

EDIT - I read that you tried the all-at-once. I'll think about what else it might be if you already tried that. What happens when you connect a servo tester to one of them?
Problem solved!!!! I used a Y harness this time to power the Pixhawk through the motor one port. Previously I had been powering it through the Aux 9 port. This time the ESCs initialized without an issue!!! So clearly opto is very important, haha. Thank you!

Let me tell ya, the sound of 8 U10s running together is pretty intense.
 

jipp

Senior Member
#60
looks like a fun class. i can not see a 250 class lifting much more than 1 beer. maybe 2... but that be pushing it maybe? i could be wrong tho. heh.
chris