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Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
Rather than using a mechanical slip ring, you could potentially transfer the power and information using inductive coupling. Something like Manchester encoding has one guaranteed transition per cycle, and then you just bung the signal through a rectifier/smoother to pull off the power.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Another option, especially for batch/mass production, is to etch the slip rings into the PCB, with 'through hole' connection, so the wires are on the reverse side of the board.
EDIT: You obviously also mount the motor on the reverse side of the board too
Registered Member #230
Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284
Putting any form of energy through a ball race will speed its demise. This problem is apparent with variable speed drives harmonic energy destroying the race surfaces by micropitting due to EDM
Registered Member #191
Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720
johnf wrote ...
Putting any form of energy through a ball race will speed its demise. This problem is apparent with variable speed drives harmonic energy destroying the race surfaces by micropitting due to EDM
Yes, it is called shaft current, and that's why they use insulated bearing at one end of the shaft to break the loop. However I think even smaller bearings can handle serial communication signals. One way to increase current handling is a slight preloaded, it should mostly eliminate arking and increase link reliability. Drawback is slightly increased drag.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
In a sliding contact there is a relationship between the amount of charge transferred and the pressure between the conductors. At worst, at high speeds the surfaces ride on air and the thing acts like a capacitor. If the brushes use carbon, it works when the com surface also has a electrographitic surface. Perhaps this not a place to waste time on.
If you had eight stationary LEDs in a circle, connected to a ring chaser, sending a burst at its appointed place in the circle, a spinning photo diode could extract angular position, and when in sync, a certain LED, be read for data as it was passed over. 8 frames of data/rev Fodder for a PIC program.
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help! serial communication across moving contacts.
