Crazyflie w/ Double Motors

[Surrender]

I was successful with pairing them, i solder only one wire per time. It is also running without any problems. But if anyone also do this, please have attention with the wires, they must not create a shortcircuit!

I can fly now the double time (as lang as with a normal crazylfie).


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[KaR]V[aN]

I didn't mean that. Batteries also have internal resistance so the resistance of each cell should be paired. If not, one of them will discharge over the other leading to an infinite discharge loop between both cells discharing so fast that cells may catch fire.

I don't know up to where the protection circuit protects the cells but I would be really careful as LiPo batteries can be dangerous if you're not really familiarized with them.

[Surrender]

Hm i don't know exactly what you mean.
What u mean with "paired cells" and with the infinite discharge loop?

I only recognised that the batteries get much hotter now when flying. But there was nothing, also when i was flying outsite @ 40°C Air temp


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[absoloodle37]

Concur w/ Karvan. I had a LiPo fry on my when I was swapping connectors. When outside of the plastic JST-ZSH connector, the two metal leads can accidentally touch eachother, causing a short. I got sparks and the insulation on the black and red wires immediately melted off in a gloopy mess. Then I burned my fingers pulling the leads apart again--thankfully before they melted together. Those LiPos are no joke. I've seen youtube videos of LiPos exploding in a ball of molten napalm. Never leave them unattended without at least one lead insulated so they don't accidentally touch together. They could easily start a fire in your work area.

No one likes to explain to the fire department why they're an idiot...

[Surrender]

That is why i only worked with one free wire and not with both.
I know they are dangerous, also from videos. I was very careful with handling those while soldering wire by wire.

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[absoloodle37]

Awesome! Good on you. Just sayin'.

[absoloodle37]

Tobias/everyone,

I'm still working on my double-motor configuration w/ FPV. Double motors allows me to carry a 600mAh battery and fly for over 10 minutes! I took your advice and used the VCOM (Pin# 16) and DGND for my FPV transmitter that I bought from FPVhobby.com. After hearing that 2.4Ghz can cause interference with the control frequency, I went with a 1.3Ghz 50mW tx that draws 180mA w/ the camera. I also have a voltage regulator (5V step-up from Pololu) that I haven't installed yet.

2013-10-06 21.30.11.jpg (48.24 KiB) Viewed 8100 times

Heres my problem:
The problem is that when I throttle up, I lose control connection with the crazyradio. The Tx works fine-- even at full throttle I get a pretty clear picture with only minor distortion from engine noise. Eventually, the camera will drop out once output voltage gets below 3.4V (which is why I will install the 5V step-up soon). To troubleshoot, I've disconnected the camera and throttled up, and the control link stays solid (flashing green light & full control). Plug the camera/tx back in to VCOM and I lose control link as soon as I throttle up. When I plug the CF into a USB power source and establish a link, the control link holds fine at full throttle--even with the camera/tx plugged in.

Based on my findings, I think the battery doesn't have enough power output to handle eight motors at full throttle and a camera/Tx (180mA). Would this make sense? If I went with a lesser power transmitter (10mW tx at 140mA instead of 180mA) do you think that would make a difference? Should I get a higher output (30C?) battery? Can I configure the PCB in any way to increase current from the battery?

Thanks for your advice!
Ryan

[tobias]

Very nice build, like it a lot!

We have noticed similar problems, that when the system gets too loaded it tend to drop the radio link. As a first simple test try switching to 2M datarate on the radio. It might decrease the radio distance but we have noticed that the link is more stable during heavy loading.

[absoloodle37]

I tried switching to 2M, using various channels but that did not work. The CF lost signal as soon as I got a few feet away from the crazyradio. Considering the camera draw is 180mA, should I switch the camera's power source to VCC (rated up to 200mA), or would that not help? I guess I would run the risk of overheating the VCC regulator...

I can also try to find a 35C battery and see if that would help, given the current of VCOM is rated up to 4A. I could also return the 50mW TX/camera (draws 180mA) and get a 10mW TX/camera (draws 140mA), or do you think the 40mA decrease in current consumption won't help? Also, do you think the addition of the 5V step up regulator would help or hurt the situation? I can fly without it for a short period of time...

I guess the last resort would be to pack a second battery dedicated to the camera/tx, but the extra battery and cabling means extra weight.

Obviously I can try all these options, but which one should I try first? Thanks for your thoughts on this!

Ryan

[tobias]

I would try the 5V step-up connected to VCOM and DGND as a first step. That will help isolate the systems from each other.