Getting data from a rapidly rotating device.

Hi,

I need to get data from a rapidly rotating shaft to an external receiver.

My current plan is to have a battery powered mini-pro strapped to the shaft (spinning at about 10,000 rpm) and connect it to a bluetooth modem (also on the shaft).

It would then transmit it's data to another arduino with a 2nd bluetooth modem.

My question is this, will a bluetooth modem still transmit viable data whilst spinning rapidly? Are there likely to any problems with polarization or alignment of the two modems? Or is there a better way to transmit the data?

Thanks

My current plan is to have a battery powered mini-pro strapped to the shaft (spinning at about 10,000 rpm) and connect it to a bluetooth modem (also on the shaft).

Are you nuts? What do you think that is going to do to the balance of the shaft?

will a bluetooth modem still transmit viable data whilst spinning rapidly?

Radio waves don't care.

Or is there a better way to transmit the data?

Perhaps you should start with what data you expect to get from a shaft spinning at 10,000 rpm.

Are you nuts?

Possibly

What do you think that is going to do to the balance of the shaft?

The shaft already weighs a lot so my guess is 'not much'. It already has an instrument enclosure built into it that is designed to allow the electronics to be installed on the center of rotation. 10,000 rpm is the design limit, normal operation is slower.

Radio waves don't care.

thanks, that's what I needed to know.

It already has an instrument enclosure built into it that is designed to allow the electronics to be installed on the center of rotation.

That's a whole lot different from "strapped to" the shaft, which is what you first said.

What material is the shaft made of? What material is the enclosure made of? Are you really going to get radio waves out of the enclosure/shaft?

What material is the shaft made of? What material is the enclosure made of? Are you really going to get radio waves out of the enclosure/shaft?

I've not actually seen it yet, the spec. indicates a large part of it consists of boron carbide. I believe the instrument chamber has at least one open side. I'm concerned that even if radio waves can get out in one direction, they may not get out in all directions. If I can install the mode right at one end of the shaft, then it may be ok.

Actually, radio waves are subject to doppler shift. If the transmitting antenna was significantly off-axis and the receiver perpendicular to the shaft, there would be an apparent warble in the received frequency. But the effect is going to be insignificant (hard to measure, even if you wanted to) at the speeds and distances we’re considering here.

Fulliautomatix:

What material is the shaft made of? What material is the enclosure made of? Are you really going to get radio waves out of the enclosure/shaft?

I've not actually seen it yet, the spec. indicates a large part of it consists of boron carbide. I believe the instrument chamber has at least one open side. I'm concerned that even if radio waves can get out in one direction, they may not get out in all directions. If I can install the mode right at one end of the shaft, then it may be ok.

And this one?

Perhaps you should start with what data you expect to get from a shaft spinning at 10,000 rpm.

what data you expect to get from a shaft spinning at 10,000 rpm.

Again, I'm not sure, the instrument generating the data is an SEP (Someone Elses Problem), internal stresses, radiation levels, temperature and other stuff. Just data.

Perhaps an old fashioned set of slip rings or alternatively rings of series LDR's maybe IR one set for high and one set for low data.

Must admit, my first impression was one of "Arduino in orbit"... :astonished:

My current plan is to have a battery powered mini-pro strapped to the shaft (spinning at about 10,000 rpm) and connect it to a bluetooth modem (also on the shaft).

Stress due to centripetal forces will be an issue for the mini Pro surface mount components; especially with no conformal coating. Vibration will exasberate solder fracture. Some effort should be made to ensure the instrument package is aligned and secured along the centerline of the shaft, minimizing horizontal displacement.

If the battery is LiOn, you may wish to contact the manufacturer to determine is issues exist with seals and internal construction. LiOn can be a bit nasty when shorted internally.

Ray

Put it on a turntable that spins at 10,000 rpm in the opposite direction. That way it will stand still.

My thought would be to wind a coil around the shaft and feed your data into that. Another nearby stationary coil (best would be a concentric one) can then be used as a pick-up. If you make your baud rate slow enough (say 100 baud to start with) to avoid hysteresis problems, it shouldn’t matter what speed the shaft is turning at. This transformer-like arrangement will only work on the rising and falling edges of the signal, but it should be easy enough to turn that back into a square wave. And it should work in both directions, if feedback is needed.
You could try uploading a sketch to the Arduino while it’s turning at 10,000 RPM. That would be a first! :slight_smile: :slight_smile: