Small light Open Source/HW electro-permanent 10kg (ideal) cargo holding magnet for the DIY multicopter drone and robotics communities
I stumbled upon this idea by reading this great article by Travis Deyle about electro-permanent magnets. These magnets are programmed (on off) with a current pulse. No static energy is required. Changing the magnetic field does require energy and is in the hundreds of mJ for our purposes. These electro-permanent magnets are just as strong as Neodymium magnets.
pdf link to the PHD thesis covering this is on the project page
there been a lot of concern of magnetic interfence with the compass, so here is the spiel
there should be no external field since the field lines are closed through the cargo iron in the on state or through the iron in the device itself.
in the prototype the iron goes beyond its saturation, the thickness should 1mm not 0.5mm same goes for the target. looking at the theoretical performance and the prototypes performance about half the field leaks, eg are not going through the metal. i expect the leakage to go down to below 10%.
a laser cut iron cover covering the magnet itself with some distance in the 5mm range, less 0.1mm thick will absorb the rest of the leakage. we should have a factor of 100 maybe 1000 that we can reduce the external field before one has to invent crazy things. mu metal might give us a few orders of magnitude more, but since its low saturation and some other factors i need to the math to get a quantitative idea on its performance.
long story short simple easy to implement shielding with proper construction should allow one to mount the compass right on top of the magnet
I hope you like my project and am looking forward to some feedback
http://www.kickstarter.com/projects/412473553/opengrab-open-hardware-electro-permanent-cargo-gri
Comments
there is an update in the post regarding compass interference...basically there will be no problems
Anybody knows if this permanent magnent can affect to the readings to the magnetometer?
How much distance we need to keep?
Worst-case, one should be able to cancel out any magnetic side-effects by using two magnetometers at two different known distances to the EP magnet. (as long as you're not saturating everything to hell of course). And as a bonus, you get a measure of the magnetization of the EP magnet :-).
Ah yes I see it now - looks promising. Well you have my money in the kickstarter so hope it helps!
What kind of power consumption will it have while active?
That design looks awesome dude - I've thrown $45 at it so far! Also, how heavy is the magnet assembly itself going to be out of interest?
No fair that my fully assembled $50 twig didn't get funded, but the electromagnet does.
We've discussed this elsewhere, but I believe it to be a non-issue. As long as the magnet is far enough away from the APM. We'll see, but I'm confident it's either not a problem, or easy to solve with MuMetal.
I have HUGE magnets in the 3800W motor on my heli, and it's not causing a problem.
And the pulse, worst case you'd get a little blip of yaw.
How much does mu-metal cost? Covering all but the business end with such plating might attenuate the magnetic field a little bit. Also, can the current compass library learn two different states of a source of static magnetic interference?
-
1
-
2
of 2 Next