Detectable Ballast Interference

If you are talking about the ballasts in newer fluorescent lights, then yes there is lots of electrostatic interference. In my office the interference is at ~25 kHz, but I=92ve heard of higher frequencies also.

George H.

RMCG wrote in news: snipped-for-privacy@news.x-privat.org:

Probably not. Powerful lights with fittings designed for warehouses placed in domestic greenhouses and growrooms put high energy fields normally given plenty of space, into close proximity with devices not made to tolerate it.

One thing you can do is shield ballasts with metal cases and ground them (should be already), and use star network grounding instead of ring mains. If you have a shower or cooker outlet you can do this without rewiring the house. Ground loops are usually a problem for mains frequency itself but they're not filtered, low mains frequency has no monopoly on use of a ground loop if it's there. One possibility is that lamps become small antennas, in which case a grounded fine metal mesh can screen an enclosure's front to let light out. That's worth doing given the explosion risk from HID lamps anyway. If you can afford it, you can buy braid-screened mains cables.

So use shielded cases, grounded, to control source, and star network grounds to avoid loops and help reduce noise in sensitive gear. Other than that you're at the mercy of makers who aren't designing for this kind of setting. (Discrete growrooms close to living spaces).

Naw in HPS.

Lostgallifreyan wrote in news:Xns9DDFDE203F76Dzoodlewurdle@216.196.109.145:

Another thing you can try is ferrite rings, slugs, etc. eBay knoweth where.... A lot of interference might be only at a few KHz but if it's got hard edged pulses at RF it will propagate to radios and hifi gear. So if you put ferrites on cables (same as on monitor cables, etc), you might 'blunt the edges' of some signals so they don't get noticeably rectified by transistors and diodes in sensitive stuff, or by bad joints in wiring. Ferrites can be found cheap, if you keep looking...

Indeed -- our office has some that interfere right around 450kHz, although I've never bothered to look into whether that's already a harmonic or the fundamental.

Chances are, these aren't from lamp ballasts but from PC power supplies.

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Get an oscilloscope and wave the probe around the lamp fixtures.

I've seen impressive amounts of 40 KHz crud around flourescent lamp fixtures.

Why does it matter? Is this one of those EMI-causes-cancer things?

John

They go away when you turn off the lights?

Oops, no, then it's the lights :-)

Although, the noise from my old Dell inkjet printer supply dropped to a much lower level when I turned off the lights. Which was rather weird but it really came from there.

If it's CFLs maybe get new ones. I have the Philips Marathon here in the lab, they are fairly quiet.

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They definitely give off low frequency radio energy. Some fluorescent bulb ballasts use RF emission through the glass to assist starting. All the electronic ballasts that I've seen require the entire circuit (wires, ballast, bulbs) to be in close proximity to grounded metal to catch the leaked power. Go to a hardware store and read some installation manuals.

In most cases the radiated power drops off too quickly to bother anything. I have experienced problems working on exposed audio and AM radio circuits under electronic ballasts. Adding a few more feet of distance always solved it.

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The "old" transformer-based ballasts (by themselves) had little RFI radiation; the solid state ballasts are noisy and detectable. But bear in mind that the fluorescent tubes themselves have ALWAYS been noisy and the worst culprits.

Joerg wrote in news: snipped-for-privacy@mid.individual.net:

That's why I mentioned lamps as antennas. :) Although in this case I think the whole lighting circuit extends the antenna existing in the mains circuit.

If there's a single source it can be isolated, otherwise there#s not much people can do unless there is a major paid incentive for designers of lamps and other systems to be more rigorous about emissions.

I'm not sure about this, but as far as I can make out, the noise compliance notices on stuff are far more lenient and arse-covering than they used to be. They used to emphasise a sense of security from noise according to given standards, now, they seem to tell the punter to expect it and put up with it.

Kevin McMurtrie wrote in news:4c76010f$0$22119$ snipped-for-privacy@news.sonic.net:

Fascinating. Next time I see someone asking for a cheap DIY Oudin coil I might mention that. :)

You mean CFL ballasts ? Or just old-fashioned standard flourescent tube ballasts ? Both will certainly generate 'interference' of some kind.

What's the real question ?

Graham

What's HPS? High Power... Sodium?

George H.

I can tell you we had a situation a few month ago where a couple of lights in a parking lot (sodium vapor, I think) were emitting enough interfernece to cause problems for a cell site receiver setup, atop a

5 or 6 story rooftop, less than 1/4 mile away. So, that would be 850 MHz, ~1,000 feet, and the receivers used at modern cell sites are "very" sensitive. Active gain and filters, etc... May not be the same as your situation.

George Herold wrote in news:aa3f9942-3365-4c34-b0fd- snipped-for-privacy@v8g2000yqe.googlegroups.com:

Almost... high pressure sodium.

A lot less stinky than high pressure selenium.

fd-

As a possibly interesting aside -- when shooting digital photography at high speed without flash under flourescent light, the white balance will shift slightly according to where in the 60 cycles the light source is at, at the exact moment the shutter opens. I don't know if this is the case with sodium vapor lights? I suspect it would be. Ditto for mercury vapor lights, although that would occur a much higher K temp, and perhaps not as noticable of an effect (at least, not in a photograph).