More powerful coreless motor

Firmware/software/electronics/mechanics
Alfredvc
Beginner
Posts: 12
Joined: Tue Apr 29, 2014 10:54 pm

More powerful coreless motor

Post by Alfredvc » Fri May 09, 2014 4:34 pm

I was wondering if it was possible to fit the crazyflie with more powerful coreless motors.
I have looked at two alternatives so far:
Are any of these alternatives viable?

Birdman
Beginner
Posts: 6
Joined: Sun May 11, 2014 2:01 am
Location: San Francisco Bay Area

Re: More powerful coreless motor

Post by Birdman » Wed May 14, 2014 7:40 am

I have just ordered my CrazyFlie and I to am interested already on what the chances of running a little bit bigger motor. I am going to look into it for sure. 8-)

tobias
Bitcraze
Posts: 1818
Joined: Mon Jan 28, 2013 7:17 pm
Location: Sweden

Re: More powerful coreless motor

Post by tobias » Wed May 14, 2014 8:37 am

The power system itself can handle up to maybe 15W continuous (~1A per motor) but if too much power is drawn it tend to degrade the radio performance (then 2 Mbit mode tends to work better). We have successfully tried 7x16 motors but 7x20 motors should work as well. You should probably upgrade the battery when you do this as well.

Alfredvc
Beginner
Posts: 12
Joined: Tue Apr 29, 2014 10:54 pm

Re: More powerful coreless motor

Post by Alfredvc » Wed May 14, 2014 11:13 am

Thanks for the answer!

I have been looking more in detail into replacing the motors since i will be needing more power and a slightly larger frame and have narrowed it down to three choices:
More information about the motors among with many others can be found at http://www.rcgroups.com/forums/showthread.php?t=2009496

Would it be possible to use the 8.5x20mm motors or would this be too much for the power system to handle? If so, is there a way around this?

tobias
Bitcraze
Posts: 1818
Joined: Mon Jan 28, 2013 7:17 pm
Location: Sweden

Re: More powerful coreless motor

Post by tobias » Wed May 14, 2014 11:56 am

There are some factors that limit the current.
1. The battery. The 170mAh battery for the Crazyflie has a protection circuit (PCM) to cut it off at over 4A continuous. Switch to a bigger and better battery.
2. The battery connector. Can be worked around by switching to a better connector or soldering the battery directly.
3. The board traces. These can probably handle 10A but has not been tested or calculated. External wires could be soldered to increase current capability.
4. MOSFETs. These should be able to handle at least 3A per motor.
5. The noise the increased current generate. This is probably the most difficult factor to handle but could be helped by putting decoupling capacitors between ground and the battery connected motor terminal.

Then there is the issue with the added weight, vibrations, etc which have to be taken care off.

So by taking care of the above you should be able to use the 8.5x20mm motors. Please let us know what you decide and how it turns out!

Alfredvc
Beginner
Posts: 12
Joined: Tue Apr 29, 2014 10:54 pm

Re: More powerful coreless motor

Post by Alfredvc » Wed May 14, 2014 1:32 pm

Tobias,

I will indeed get a bigger/better battery and probably replace the battery connector for the regular rc jst connector.

Do you have any more information on the trace width/copper thickness or any other way of calculating the max current of the traces? If not, i think i will have to go for the 7x20mm since the bigger 8.5x20 will draw around 11A max all together.

If im not wrong about the decoupling capacitors, they should be placed as close as possible to the motor on the + and - cables right?

Ill definitely post the progress of the project! I will start in the beginning of june but want to order the parts now so i have them by then!

tobias
Bitcraze
Posts: 1818
Joined: Mon Jan 28, 2013 7:17 pm
Location: Sweden

Re: More powerful coreless motor

Post by tobias » Wed May 14, 2014 2:55 pm

It shouldn't be too hard to put an external +BAT wire. Or even easier, you can solder all positive motor wires directly to the battery connector (if they are long enough). Then that wont be an issue. Then you can also easily solder a capacitor, try maybe 100uF, between + and - on the battery connector.

The decoupling capacitor should be between +BAT and GND and not the + and - on the motor cables.
Attachments
CF VCC layer.png

Alfredvc
Beginner
Posts: 12
Joined: Tue Apr 29, 2014 10:54 pm

Re: More powerful coreless motor

Post by Alfredvc » Wed May 14, 2014 3:24 pm

Thanks for all the informative replies! Ill get started on buying the parts!!

piesi
Beginner
Posts: 6
Joined: Thu Jul 10, 2014 8:34 am

Re: More powerful coreless motor

Post by piesi » Thu Jul 10, 2014 8:45 am

Hi,
I made some experiments with the 8.5*20 mm Hubsan motors and
wrote my results down here:
http://frankpiesik.info/2014/06/01/crazy-experiments/
To hold the motors and safe the cf, I've made some 3d-printable frames
you can download here:
https://github.com/Piesi/pCraze


greetings!

omwdunkley
Expert
Posts: 162
Joined: Thu Jun 06, 2013 9:56 pm
Location: Munich

Re: More powerful coreless motor

Post by omwdunkley » Fri Jul 11, 2014 6:00 am

Awesome! Id love to see some videos))

Post Reply