So a week or two ago they put new LED T-8 (4') bulbs overhead in my lab. Today I was doing some noise testing and I wondered how 'bad' the new bulbs were. They are great, a quick survey and I could see no peaks in my noise spectrum. So I grabbed a photodiode to look at them... The light is a beautiful 120 Hz signal.
When I looked close in (AC coupling, same gain for photodiode) there are 'steps' at ~50 kHz... but dang small.
Sweet! George H.
Wow, that's amazingly good! I know the old-style T12 fluorescents in our lab are fairly noisy. Horrible noise when the rapid-start circuit is lighting the lamps, and then some noise when they are running. But, in a crazy way, that is good, as we do a lot of noise-susceptible gear, so if it runs well in the lab, we know we are in fairly good shape for EMI susceptibility.
Jon
We have fancy new LED lights in our office. I threw a wire on top of one, to a scope, and found essentially no EMI. Fluorescents with electronic ballasts are terrible.
They also have annoying smart motion sensors, required by law here. I disabled the one in my office, because I don't much like overhead lighting and they were always turning on and off when they felt like it.
They are 10 volt dimmable, which I might get into with a pot some day. Meanwhile, they are just off.
The whiteboard light kept falling off the cabinet, so I added LED spots.
and a dedicated camera.
I test the electrostatic leakage on this noise box with the overhead lights... or use to... I'll have to ask them to save me a ballast and tubes for testing. I think they are throwing them out.
I could build my own electrostatic noise source.. but it might be illegal.
George H.
The boss just replaced all the lights with LED tubes he got on eBay (or, really, who cares where). They flicker all day. Especially when the fuser element on a printer warms up to print.
He now wants to spend money on line conditioning equipment (which I suspect may not help). Oh, and the dimmable LED's he bought from Alibaba (or again, who gives a shit?)... they don't DIM.
Perfect.
This is the same guy who manages the SIP phones in our office, and most of the network (except for Engineering). On most days, ours is the only network running. It's too bad he's the boss or all these problems could be fixed. But I've given up. The office lights flicker so much now that you hardly even notice. But at least they're at full brightness.
The name on the bulbs is Starco lighting... huh they seemed to be based out of the same building I work in... that explains a lot.
George H.
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