Design Question: Wiring & Motors

[alemus]

I am seeking help for a design solution to run wiring through a rotating shaft spun by a motor. Imagine a display mounted on the end of a ceiling fan blade - The signal and power for the display would need to come through the motor (from the within the ceiling) while the entire blade assembly is in continuous rotation. This is not the actual implementation in mind, but it plainly illustrates the design challenge.

I am guessing this problem has been solved and there are standard terms for the parts/methods for this function.

Thanks in advance for any feedback...

 

[berkeman]

I am seeking help for a design solution to run wiring through a rotating shaft spun by a motor. Imagine a display mounted on the end of a ceiling fan blade - The signal and power for the display would need to come through the motor (from the within the ceiling) while the entire blade assembly is in continuous rotation. This is not the actual implementation in mind, but it plainly illustrates the design challenge.

I am guessing this problem has been solved and there are standard terms for the parts/methods for this function.

Thanks in advance for any feedback...

Can you use RF for the data portion of the signal?

 

[alemus]

No, RF is not an option. The challenge is to run wires (signal + power) while allowing axial rotation.

 

[berkeman]

No, RF is not an option. The challenge is to run wires (signal + power) while allowing axial rotation.

Well, I can think of at least one good way to do it. What are your thoughts? It sounds like a school project, so you need to do some research on your own and throw out some ideas here.

What voltage and power level are required? What is the bandwidth and nature of the data stream?

 

[Topher925]

Usually things like this are done using slip rings.

http://en.wikipedia.org/wiki/Slip_ring

Its also very common for things like torque transducers to use AC coupled coils for transmitting power, sort of like a rotating transformer.

 

[alemus]

Berkeman - This is not a school project. I am a hobbyist working on a robotics project.

Topher925 - This is exactly what I was looking for. I knew there must be some standard practices for this, I'm just not versed in the terminology. THANKS!

 

[schip666!]

Running signal through slip-rings can get noisy, I'd look into other ways to move data.

For power, I've been wondering if one could use the brushes and armature of a regular motor -- probably with a diode bridge on the receiving end. Anyone tried that?

The rotating transformer idea sounds pretty cool, never thought of it...

 

[paa10000]

I agree with schip, slip rings would be noisy. However, they would be simple and would work if you have a very simple (slow), fault-tolerant communications stream.

If you need better data transfer and you have power on both sides of the moving object (which can easily be supplied by slip rings), you might try optical communications (i.e. IR rather than RF). You need to have a fairly clear line of site between the receiver and transmitter and you have to take into account that the receiver needs to pick up while the object is rotating. However, this method has the advantage that there are already a lot of devices for delivering/receiving IR signals on the market.

 

[Bob S]

The standard solution would be slip rings. There are two basic types; the cylindrical slip rings (can be mounted anywhere on rotating shaft) and the radial ones (mounted on either end). In both cases, the drive shaft is hollow, and the wires are inside. See one example of slip rings (2 terminal, 4 amps, 1200 RPM) at

http://www.mercotac.com/html/205.html

Bob S