For an art installation i am using 2 magnets that i am controlling with arduino that are attached on either side of a iron bar .
The magnets are powered by using a 12V 32A DC adaptor.
The arm the magnets are attached to is hooked up to a motor that rotates the iron bar.
the only problem is that the wires will get tangled up after rotating for a while.
I need a electrical contact which can handle the current that is given by the adaptor and can rotate.
Does anyone have any suggestions how I can build/buy something like this?
Does anyone have any suggestions how I can build/buy something like this?
Depending on the design of your project, you could probably make some slip rings out of copper pipe sections with braded copper wire running on the rings.
12V 32A ??? That's a massive amount of power for an electromagnet, how big are these things? For that large an inductive load you'll need well engineered slip rings, or risk
the things spot-welding themselves...
I soldered 2.5mm² wires to the inner and outer ring of the bearing to provide better connection than the example though.
The only problem that I'm still experiencing is that the resistance of the slip ring is varying very much... (Peaking at 5kOhm, which is unacceptable for high power transmission), although I'm thinking that this could be solved by removing the grease inside the bearing (especting this to cause the high resistance).
I haven't been able to experiment enough with it though.
My idea was to use this to avoid twisting wires on my windturbine... But the power lose is just too much at this moment.
Although it might be useful for signal currents.
I'd like to have other people thoughts on this idea.
Ward123:
I'd like to have other people thoughts on this idea.
That's not a bad looking construction; likely your losses are through a combination of the grease, poor contact, and the materials (the poor contact of the balls and the type of steel probably all adds up, and the grease doesn't help).
What you might try is to remove the plastic shields from the bearings, then flush the old grease out with brake cleaner, and try running them dry. If you absolutely need lubricant (I wasn't sure where you planned to use this slip ring assembly at on your build) - then maybe you might look for a conductive grease (perhaps "silicone bulb grease" sold at an auto-parts store?) to re-pack the bearings with.
That - or ditch the bearings, and go for a copper ring (copper pipe segments) and carbon-brush arrangement (you can get replacement motor brushes for dremels or larger motors - check hobby shops, too - or build your own from carbon rods from carbon-zinc D cells).
I had some other bearings laying around, (couple of fakes and one legit SKF brand)... guess what, that SKF bearing had like 0 Ohms between inner and outer ring, the fake ones multiple kOhms... maybe it's situated in the kind of alloy used for these bearings? Indeed it would be an idea to remove those seals and clean the grease. Its for the horizontal rotation of a wind-turbine, so the bearing won't make much revolutions (more static, only when the wind changes direction). I'm more worried about the bearing balls welding themselves to the bearing rings with high current/voltage...
-btw- credits of that wonderfull construction go to the maker Stephan Schulz, I wasn't able to make a picture of mine due to the gray pvc tube around it (wouldnt show a thing .
about those carbon contacts, doensn't they wear out quiet quickly? My idea was to use those bearings so that I didn't have to replace the carbon that often, because it's hard to reach the coupling 7m in the air
Carbon contacts last for quite a while in high speed universal motors. So it isn't even slip rings, it is on a commutator which should wear carbon brushes out more quickly. High speed rotary tools like the Dremel use them. I think they are self-lubricating.
No, I'm using regular deep groove roller bearings (inner diameter 20mm), the load on these bearings will be almostly zero, because they are only used to transfer the current.
I'm hoping that you're on the same thought that using wires soldered to bearings is much easier than those messy carbon contacts, which have to align perfect, need springs and copper tubes etc.?
I mean you said that the bearings in the wind turbine turn only slowly, if at all.
Use what works for you. If the ball bearings are working, keep using them. Those messy carbon contacts have been working for a century in motors. I'm not saying switch, I'm saying don't discount them.
