That reminds me of the plastic they sometimes use in commercial displays: when illuminated with UV from fluorescent lights it appears to fluoresce itself, emitting bright colour along the edges. Going with your suggestion, a side illuminated fluorescent ring might be a solution, assuming it has a fast-enough decay.
-- Joe
Exactly those. Plus if you use visible light it'll dazzle visitors. Or when using IR at least add a blue LED for that cool look.
Decay may not be a big deal, depending on how large it is. Spehro only needs data rates around 10Mb/sec. Even if there is a chance that there'd be a beat with the modulation frequency somewhere one can always hop that. As long as the carrier frequencies for the other direction are far enough away so cheap filters will do.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Will an "antitwister" work?
If Google groups screwed that up just go to the US Patent Office site and look for patent #3,586,413 by D. A. Adams.
Mark L. Fergerson
I don't mean it will be so dim you can't see it, only that the loss will be high for datacom. If the OP can afford the power, great.
Cheers,
Phil Hobbs
I would look into some type of 'leaky' light pipe, possibly just a lucite ring with a flat edge that has been ground into an emitting surface. You direct your source along the axis of the tubular ring, and let defraction emit it out the edge...
Charlie Edmondson Engineering
Well, I did say I wanted to minimize the power consumption a few lines above..
Can't really spare all those watts. Maybe 5% of that.
Spreading out the light means that it is far, far dimmer, which complicates things at the optical front end. Simpler is good. Otherwise, I could just use a large number of LEDs run at low current and diffusers.
It looks like it should work with a relatively small number of appropriately aimed transmitters, or as a backup the large number with selective enable looks doable.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Optical slip rings are available commercially from people like Moog (the industrial components people, not the synthesizer people). You can get ones that only have fiber (Moog calls these a "fiber-optic rotary joint") or ones that have both fiber and copper channels. The prices start at a few hundred dollars and rise from there, but asking for a quote is free.
If you don't need continuous rotation, you might also be able to make a "clock spring" out of regular fiber-optic cable. Basically, you lay several turns of cable around the stationary part, and then run one end to the moving part. Car steering columns have something like this, made with a flexible circuit board, to connect to the airbag in the steering wheel to the rest of the airbag system. You aren't limited to less than
360 degrees, but you can't go forever either.Standard disclaimers apply; I don't get money or other consideration from any companies mentioned.
Matt Roberds
Do you have a power limitation? If not, just mount a bunch of LEDs in a ring, driven by the same signal. Mount them close enough together so that their beams overlap, ensuring that one will always be within the field of view of the pickup.
You could reduce the number of LEDs (to one perhaps) by feeding a fiber bundle and them distributing the other ends of the fiber around the circumference. A sufficiently fat fiber will result in the light diverging when emitted from the end. I forget how to calculate this angle, but some optical wizards might know.
-- Paul Hovnanian paul@hovnanian.com ----------------------------------------------------------------------- Have gnu, will travel.
I'm a bit late into this thread, but you seem to have left out some details. So far, the discussion seems to be assuming that the data link is unidirectional, and that the power limitations are on the transmitting side. Is this in fact the case?
So what's wrong with using a single LED and multiple detectors, or a fiber bundle feeding a single detector on the receiving side?
Just as a point of information, I once worked on a display device -- sort of a "propeller clock" on steroids -- in which we needed to supply about
100W of power to the rotating part, along with about 1 Mbps of data. In our case, we had a hollow shaft, so we just shined an IR LED into one end, and had a photodiode at the other end, about 10" away. Worked just fine, using ordinary UART signals (not IrDA). The power was transferred using a rotary transformer, driven at about 50 kHz.In your case, you don't have access to the rotation axis, but the optical path length can potentially be much shorter.
-- Dave Tweed
just a test. two posts to this thread have not shown up so far, but both issues are addressed by other posts.
RL
10Mb/sec ain't much. Why not use very short pulses at, say, 50MHz? Then you can use the ring of diodes or a disperser disk with one powerful diode. [...]
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
I was just thinking about enabling the appropriate LED (or small group) but your post didn't make the nature of the rotation clear. If the rotation is relatively uniform, where the logic on the rotor can figure out which way it is pointing, this should work.
The other thing that might work is one transmitter and a ring of receivers, if the power an hardware constraints of the stator are less stringent.
-- Paul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ Klein bottle for rent -- inquire within
Spehro Pefhany wrote in news: snipped-for-privacy@4ax.com:
Princetel makes FORJ's, and they work w/ slip ring manufacturers.
They also do custom work, if you have a big enough budget.
-- Scott Reverse name to reply
I originally thought in terms of small say 1 inch (25 mm) circular mirrors. Then you asked if you are missing something, you can do things similar to the circular mirrors with fiber optics.
Adding in the direction of transmission, which part TX/rex is fixed?
With dual transmitters the overlap problem goes away.
Hmmm. Do the same trick on both ends, get the same effect as shooting it along the axis.
Neat product, great bandwidth. But the application requires absolute non-contact and on axis placement is unavailable.
Just the same, i would like to see how they do multiple fibers at gigabit/s speeds.
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