Rotating PCB

[Jeroen3]

Hi all,

I'm exploring ways to create a rotating PCB. With LED's off course.
Mouting a PCB to a motor isn't the difficult part. Getting power to the pcb is.
I've seen people using batteries on the pcb, however, I'm afraid that causes stability problems. And batteries die.

While googling I found Mercotac, however those things are apart form expensive, all "straight". You cannot mount this on the motor axis, you have to use some mechanical system to get the part rotating. I've tried looking for similar parts, but the market seems small. Or I'm not using the correct google keywords.

Brainstorming for possibilities I also though that maybe a "wireless" power transfer could be achieved. Like wireless charging, or maybe even using some coils and some strong magnets. But I do not know if that is going to get me enough useful energy. Would it?

Does anyone have experience with these "rotary connectors", or know places that sell them?
I also found brush contacts using carbon and copper rings, this is not what I'm looking for since that creates copper and carbon dust. Not to mention the sparks and emi issues.

Any thoughts?

[Alex Eisenhut]

Yes, think about how VCRs with amplifiers on the rotating head got the power to the electronics.
It was with a transformer.
However this didn't require a lot of power and it was mounted on an extremely mechanically accurate mounting.
I'd look into magnets. I've seen bike lights with a magnet on the spoke driving a coil to light a LED.
"All you need" is to figure out how to mount some powerful magnets near the PCB and use the PCB itself as the winding.
The same idea is applied to those gyroscopes you put in your hand. Forgot the name.

[Artlav]

Look up "axial flux generator".
Basically, put magnets on the stationary part, parallel to the coils on the spinning PCB.
Essentially, your PCB will be a rotor in an alternator.

[d-chord]

Can you create a concentric pair of rings on the circuit board with exposed copper?  You could have a pair of contacts that delivers power to the ring as it rotates.  This would be similar in construction to a multimeter switch mechanism but the rings are continuous.

-David

[DanielS]

Use the motor shaft as one conductor, now all you need is a brush or two... or three between the motor and a circular track on the rotating PCB - the multiple brushes reduces arcing wear on the brushes and track since you will rarely if ever break contact to all three points at once.

[eneuro]

Brainstorming for possibilities I also though that maybe a "wireless" power transfer could be achieved. Like wireless charging, or maybe even using some coils and some strong magnets.

Maybe something like this depending on PCb size and other project requirements? Free energy rotor device I've used in this magnetic stirrer 


Don't tested my wireless charger based on rotating strong HDD nedynium magnets so far, but everything needed is in old hard drive including nice 3 phase BLDC motor

[Jeroen3]

Current may never flow through a bearing, the bearing will spark, the grease will catch fire and the bearing will lock up. (on megawatt alternators. But this still applies to small bearings.)

An axial flux generator looks good, but that requires some huge mass to be rotated, through air. I was thinking about two small coils pasted on or winded through the pcb.
Giving those coils an continuous stream of (North-South-North-South) neodymiums mounted on the base. That should have some effect. But I guess the only way to know is to try.
I've worked on a LED project with 64 RGB LED's, these could draw about 3 to 4 Amps when all max white. That kind of power is probably not going to happen.

I did also find "pancake slip rings" which looks promising. However, coils have more challenge.

[AlessandroAU]

The easiest way is just a simple air gapped transformer. I've done this before on a propeller clock project.

I used a PC case fan with the fins removed so I just had the motor unit. About 150 turns of wire around the motor as the secondary and the primary former was made from a soda bottle. These pictures are pretty old and don't show the part in full detail but you get the idea. To drive the primary I used a 555 and a transistor H-bridge, frequency was a around 30khz, on the other side some UF4004 diodes and a LM9805 to regulate the voltage for the mirco.