Crazyflie w/ Double Motors

[Surrender]

What is better: Buy a antenna for 7 up to 20€ or buy a e-Sky transmitter for 30€ + 14€ shipping cost?

[foosel]

Depends.. if you want to tinker around with it programmatically, the antenna is probably the better idea. If however you want to experience a superb flying stability, the R/C is definitely worth the money Might even be possible to use the 4-channel version (you only need 4 channels anyway for flying the CF), which comes down cheaper. I haven't yet gotten my hands unto one of those though to test, so only go down this option if you are feeling adventurous enough and have a working return option.

[smiler]

I did buy a bigger antenna but it didn't do anything for my constant disconnections. However after getting an ESKY transmitter I haven't looked back. It's so much more awesome to fly with a control that doesn't have any play on the input sticks. Only bad things about the ESKY is that it's very large and have a very plastic feel to it.

[Surrender]

Now i have bought a antenna (9dBi, from Amazon.de, Link) for 7€ and the e-sky transmitter ET6i (from here: http://www.helihausen.de/) for 30€ + 14€ sending.

Next week i can test it out, which one is best or where are the dis- and advantages.

[TheFrog4u]

when using the esky make sure you follow the wiki instuctions and use jodell's tweaks for better flight performace (link in the wiki descriptions)

[absoloodle37]

Spent an hour getting one of the double motors mounted.

Success. Even with only one side double-motored, the stabilization compensates for the changes in weight/power. The circuit really is designed well. Maneuverability is exactly the same.

http://youtu.be/AmwariOhmjY

Will repost when all motors are doubled-up.

[tobias]

I'm even surprised the Crazyflie flies that well with only one arm having double motors. That is great and it is going to be interesting to see the final result!

[absoloodle37]

Question for Tobias:

What is the max sustained power each motor can handle? Has anyone burned one out before?

You mentioned the power paths can handle up to 15W, but the motors themselves are rated at 4.2V, 800mA on the Seeed website. Is the max power of these motors really only 3.36W? (4.2V * 800mA)

If so, double motors are a necessity to split any increased current/power from a bigger battery...

Thanks for clarifying.

[SuperRoach]

That doduble motors video looked really impressive - I'm suprised the software adapts so well!

[tobias]

Motors are a education subject on its self but I'll do my best to make it understandable. Didel has a good informational page to read more.

Heat is what destroys motors. Heat is generated mainly be the winding resistance but also by friction. The Crazyflie motors have ~2.3ohm resistance which means at 4.2V and stalled it burns ~7.6W in heat. That would kill the motor quickly. More interesting is when the motor reaches maximum power, which is at about half the maximum current. After the maximum power point the motor will just generate more heat and no more mechanical power. The maximum current at 4.2V is ~1.8A and thus the maximum power at half the current 1.8/2 = 900mA -> ~ 4.2*0.9 = 3.78W. But the winding resistance increases with heat which degrades it a bit and the maximum power degrades to about ~800mA.

With the propellers the motor draws about 720mA @3.7V so it is close to the maximum power and as the battery can't deliver 4.2V at ~1.4A it becomes around 3.4V - 3.7V instead.

A Crazyflie when hovering consumes about 5W of power (~1.4A and 3.7V).

With double motors you will get double power but also increased weight. The battery should be able to handle it but the flight time will decrease, so to compensate for that a bigger battery is needed. That will add more weight and increase power consumption, so if the battery gets to big, it wouldn't add anything.