g4lab wrote:Chris if your unit is still tingling with all the power supplies unplugged it sounds like a flash capacitor might be holding a charge for a while. Does it keep tingling for a long time.
Gene, thanks for sharing your insight. The potential for a flash capacitor to be the culprit is good to have on the radar screen. In my particular case, though, I don't think flash capacitors are involved. First, if you recall
the Bratcam's lighting stage, it physically and electrically isolates the light sources from the camera and subject stages. The lighting stage and camera/subject stages are not touching, and each sits on a wooden platform. Not visible in the linked image, there is also a sheet of non-slip rubber between the lighting stage and the wooden platform. Flashes are set off by radio triggers, and have no contact with the camera. Further, when I use small flashes, only their plastic mounts contact the Noga support arms, so they should be electrically isolated even from the lighting stage. Also, I have moved more and more toward the use of continuous light, and now rarely use flash. The halogen illuminators are suspended from the ceiling, on a wooden shelf hung by nylon ropes from wooden joists, with the fiber optic light guides lamped on the Noga arms attached to the lighting stage. So even these are well isolated from the camera, where I feel the tingling.
No doubt you know far more than I about the behavior of electrons. Is there something that makes you dubious that inductance could be the cause of the tingling? The Bratcam has a lot of metal, and it is situated above--though rather far above--a bunch of electrical cords carrying full wall power. Perhaps more importantly, the Bratcam has a number of data and low-voltage cords running to it, which, even when disconnected at their distal ends, may be crossing or lying near these wall-power cords. When the wall-power cords are disconnected from wall power, the tingle goes away. When they are reconnected to wall power (not reconnected to the Bratcam), the tingle comes back. I'll repeat and emphasize that in both the wall-power connected and wall-power disconnected cases, the cords running into the Bratcam are unconnected at their distal ends. So they should not be getting power directly, but could well be getting it through inductance and carrying this induced charge to the Bratcam. I only barely comprehend electricity, but this sounds like induction to me.
If you see holes in my thinking, please point them out! I love to learn, and value being corrected when wrong.
You asked if the tingling lasts a long time. If my memory is correct--and it might not be, as I didn't take notes--it lasted for a few seconds to a minute or two after disconnecting wall power from the nearby electrical cords. And it seemed to take a few minutes for the tingling to recur after reconnecting wall power to the nearby cords. My thought was that the rig was exhibiting both inductance and capacitance. But without good notes, this thought should be taken with a large grain of salt. As my scientist friends tell me, if an experiment isn't documented in a lab notebook, it didn't happen. A couple of solid tests suggest themselves, and perhaps one of these days, I'll conduct them. In the meantime, the issue has not interfered very much with my photography.
--Chris