Compact Fluorescent flicker

Hi John,

Wow, I didn't even think this type of configuration was available, let alone feasible. Looks like a neat little toy and (since I just got my tax refund back), I'm gonna get one!

Mike

Thanks John!

I definitely need one. I can't think of a specific use at this instant, but I'll come up with something soon!

That's 100Hz then so you're probably getting a surge for every half cycle of the mains.

That's what I figured.

BTW, I have a friend who's wife suffers from splitting headaches when they use a CF in their living room - goes away on reversion to incandescent. Must confess I was sceptical about the flicker 'til I measured it for myself. I still think 100Hz is a bit fast for a physiological response.

Unless that person is one of those sensitive to such a rapid flicker. There are going to be people who are unable to use CF lighting and when incandescent bulbs are banned, they will have to revert to gas lamps or kerosene. Ah, the price of "progress?"

They don't bother me, except that they are harder to see by, and the savings seems worth it. Not sure about the pollutants used in them and the extra care needed for disposal.

THANK YOU for quantifying this!!

All I know is, there's a lot of us going to be smuggling incandescent bulbs in the future. I'm thinking of starting a stockpile right now. Maybe I'll call it my Retirement Plan!

Note to Midwestern readers of a certain age - back in the 50s my parents used drive from Wisconsin to Illinois to buy margarine and smuggle it back home. Anybody else remember doing that?

John -

How long had the bulb been lit before you captured this string of data? Does the flicker subside after some time?

Good question! It had only been on for about 3 minutes when I took the measurements shown.

I've just tried again - got a similar-looking result (about 12.5% intensity variation) - lamp has been on for at least 2 hours.

As a cross-check, I tried with an LV Halogen desklamp - came out with a more symmetrical (sinewave-like) curve, about 5% intensity variation. This may be real - or could be down to the rats-nest wiring of my lash-up picking up anything around.

Unfortunately, I can't find my torch (US: flashlight), and I have no other source of DC lighting. Too late tonight to start digging out LEDs & doing more lash-ups. Also have no GLS incandescents to try. If I get a chance, I'll try in daylight tomorrow.

I'd like to play around (a lot!) with this - but I'm up to the eyeballs (and beyond) with paying work for the next month or two. I'll get there eventually!

"Paying work" - a useful concept indeed!

When you finally have the opportunity to proceed with your experiments, I will be exceedingly interested to hear about your findings.

An interesting physiological note: flickering bulbs, whether CFL or LED, are much more annoying and painful when seen peripherally than when seen directly. I wonder if it's a rods-and-cones thing?

Fascinating! THANK YOU for all that good information, TomFranPat!

(I'm curious - Are you triplets, or just a three-way split personality?)

Three-way split

one part nice human being,

one part hard charging police officer,

one part mystical, spiritual, engineering and physics explorer!

But you can call me Tom

I've just tried in the (fast-failing) daylight - get up to 50% random-like variations - with period compatible with the lighter/darker bits of cloud passing outside. No sign of anything periodic (as in 50 or 100Hz).

Next step (maybe tomorrow!) will be to try the daylight test - but with the CFL switched on inside a light-proof bag (to check for possible air- or mains-borne pickup).

Will keep posting when I can.

Readings now down to near zero - need to change the load resistor to get any more data - but I can barely see the keyboard, so I'll have to turn the light on & give up for now.

John.

Work? - later, maybe. This is much more fun!

This was captured with 0.5 second sampling interval (not synched to mains!) - it shows the first 4½ minutes or so of the CFL output from turn-on. Fade-up and flicker (appearing as a beat) both very evident.

Same lamp as in post #1.

Got to go taxiing Small around now. Maybe have some more fun later!

John

You should also compare various brands of CFL bulbs. I have seen visible differences in the power-on characteristics of different bulbs used in the same socket.

That's another thing on my list!

Interesting new data:

I visited my sister for a few days last week. As always, much of our time was spent in the dining room - eating, playing cards, chatting. On the last day of the visit, she casually mentioned that the bulbs in the room's overhead fixture were CFLs! I was FLOORED! There had been no noticeable flicker, no headache - I could have sworn they were nice, friendly incandescent bulbs. I can think of three explanations:

* The fixture is overhead, so the bulbs were never in my line of sight, and there was SOME light from other fixtures, so maybe my eyes didn't register the flicker.

* There were five or six separate bulbs in the fixture - perhaps the flickers cancelled out.

* Maybe her bulbs use some new technology that solves the problem! I'll ask her what brand they are.

For her part, my sister credits the lovely antique glass in the fixture - she says it filters out any bad stuff! :)

Reasons for not being affected:

"* The fixture is overhead..." etc. This is a possibility, especially given light from other (non-flickering) fixtures.

"* There were five or six separate bulbs in the fixture ..." Wouldn't swear to it, but I suspect they'd all be in phase (as it's mains frequency flicker), so wouldn't cancel (I've obviously got some more work for the Labjack!).

"* Maybe her bulbs use some new technology that solves the problem!" This is certainly possible - I'm sure the manufacturers are pulling out all the stops to improve the lamps. Thinking about it, all it should need is a longer persistence phosphor - whether there's a trade-off between persistence & conversion efficiency, I don't know.

"... lovely antique glass ..." - that's Sister talk !

BTW - after exchanging a couple of PMs with pantaz I'm thinking that maybe a Labjack User's Group would be a good scheme - given enough support. I don't have time to do much about it at present (up to the eyeballs for end-of-financial-year deliveries) - but if anyone wants to post here or drop me a PM - feel free. I'll try to share it around.

A local engineering genius tells me doesn't think the flicker is related to alternating current. He thinks CFL bulbs convert the A/C into D/C and then "chop" the signal as needed. If that's so, then it's highly unlikely that any two bulbs would flicker in sync!

Caveat: This guy's special genius in in the realm of chip design, not light bulbs, so I'd like some confirmation of his theory. Anybody out there have expertise to share?

Just did a quick check with my old 'scope. Set for line trigger, the waveform is steady as a rock! (100Hz with our 50Hz mains supply). Not knocking your mate, but if it was chopped, it'd probably be at a lot more that 100Hz.

[Labjack's got it's place (quantitative measurements, trends, data logging, ease of input to electronic data format etc.), but for some things, a good ol' 'scope is just the job!]

[Aside - interesting story about the 'scope. It's an HP 1741A (100MHz, with persistence mode). It came free with a junker of an Escort I got for £400. The garage guy said he "used to be into all that stuff" - but hadn't used it for years. He thought (correctly) that I'd give it a better home.]