I am trying to figure out what is the best why to connect sensor (or low voltage connections anyway) on a rotating object. My first trial will be positioning the sensor on a ceiling fan' blade. How can I wire the sensor so that the signal will "come out" with the other wires (from the shaft, then routed with the power cables somewhere)?
I am sure this is a silly question for lots of you, but I don't even know what is the real name to call it! At the moment I am trying to make a conductive strip fixed on the shaft which will connect to the wire coming from the blade. It's not very precise and it will surely get messy when it comes to 3 wires (i am gonna use hall effect sensors)..
I think the method you are describing would be called slip ring. I'm having a hard time imagining why the sensor and activating component can't be reversed so that the activator is rotating and the sensor is stationary.
Yes put a magnet on the blades and a hall effect sensor mounted on a stick to the ceiling.
Alternatively use an IR or laser beam in reflective or transmission mode.
Well in the radio control world many use a small and relatively inexpensive portable optical RPM meter that can just be aimed at a rotating propeller to get the speed of the rotating prop, so simple optical sensor/emitter and cleaver coding can perform the task without any modification to the fan.
You are assuming he wants to monitor rpm... there may be other kinds of sensors?
If the wired part can be stationary, you're much better off. If not, try an optical/ir or radio/rf link with a battery -- or maybe even an energy harvester if it's low wattage.