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From: brians@...
Sent: Jul 14, 2018 10:31 PM
To: [email protected]
Subject: [TekScopes] Stopping Lights from Strobing

Many years ago when I was a 'lecky, I worked on a very expensive lathe light fitting that was using fluorescent tubes.

I was amazed that a lathe actually had a fluorescent fitting because of strobe concerns but I found that the manufacturer "cheated" a bit for safety reasons.
Fluorescent light fittings In most commercial use locations have power factor correction capacitors fitted directly across the connection terminals otherwise the power metering will not be correct & there can be circulating current problems.
The manufacturer of the lathe fluorescent light fitting used a dual fluorescent light fitting with two separate ballasts & only had a power factor correction capacitor fitted to the one one fluorescent light.

The power factor correction capacitor caused a phase shift on the one lamp compared to the other.
I actually ran the fitting with no power factor correction capacitors fitted at all & with the one fitted & when the one capacitor was fitted then the strobe effect was not visible.

I suppose that it may be possible to phase shift some LED lamps as well with a capacitor if they use an actual iron transformer for the power supply so you could have dual LED lamps set up in a similar way.

On Sat, 14 Jul 2018 19:31:28 -0700, you wrote:

Many years ago when I was a 'lecky, I worked on a very expensive lathe

light fitting that was using fluorescent tubes.

I was amazed that a lathe actually had a fluorescent fitting because of

strobe concerns but I found that the manufacturer "cheated" a bit for
safety reasons.

Fluorescent light fittings In most commercial use locations have power

factor correction capacitors fitted directly across the connection
terminals otherwise the power metering will not be correct & there can be
circulating current problems.

The manufacturer of the lathe fluorescent light fitting used a dual

fluorescent light fitting with two separate ballasts & only had a power
factor correction capacitor fitted to the one one fluorescent light.

The power factor correction capacitor caused a phase shift on the one

lamp compared to the other.

I actually ran the fitting with no power factor correction capacitors

fitted at all & with the one fitted & when the one capacitor was fitted
then the strobe effect was not visible.

I suppose that it may be possible to phase shift some LED lamps as well

with a capacitor if they use an actual iron transformer for the power
supply so you could have dual LED lamps set up in a similar way.

This makes the assumption that the standard triac/scr "give me part of
a phase" is what's being used.

If we have a situation where the AC is rectified, then chopped at a
high frequency for PWM, then we're not dealing with line synchronized
anything.

For the backlights I use in several projects, the PWM is on the order
of one Khz or so. What I have to do there is to worry about the
frame/field rate interactions.

Harvey

Regards,
Brian.

I wonder how
much mercury based lighting actually is disposed of without release of the
Hg into the environment.. I do have a small cache of filament bulbs, mainly
for current limiters. I'm sure enough to outlast me.

Russ

LEDs don't flicker when fed with clean, filtered DC. The light fixture in my bedroom has three LED bulbs under the ceiling fan and they don't flicker under normal usage. Just before they fail, I have had some start to flash at irregular intervals. All of the LED lamps I've see tell you not to operate them base up, but the only sockets that are base down seem to be table lamps and some outside lamps. I first installed some puny 1.5W LED lamps at the gateposts for my driveway. They were still working when I replaced them with some 7 watt bulbs. In total, there have been LED lamps there for over 15 years without a failure but it is cool when they are on. I've had two failures in two years in my bedroom where they started to flash, then they died.


Michael A. Terrell


-----Original Message-----

From: brians@...
Sent: Jul 14, 2018 10:31 PM
To: [email protected]
Subject: [TekScopes] Stopping Lights from Strobing

Many years ago when I was a 'lecky, I worked on a very expensive lathe light fitting that was using fluorescent tubes.

I was amazed that a lathe actually had a fluorescent fitting because of strobe concerns but I found that the manufacturer "cheated" a bit for safety reasons.
Fluorescent light fittings In most commercial use locations have power factor correction capacitors fitted directly across the connection terminals otherwise the power metering will not be correct & there can be circulating current problems.
The manufacturer of the lathe fluorescent light fitting used a dual fluorescent light fitting with two separate ballasts & only had a power factor correction capacitor fitted to the one one fluorescent light.

The power factor correction capacitor caused a phase shift on the one lamp compared to the other.
I actually ran the fitting with no power factor correction capacitors fitted at all & with the one fitted & when the one capacitor was fitted then the strobe effect was not visible.

I suppose that it may be possible to phase shift some LED lamps as well with a capacitor if they use an actual iron transformer for the power supply so you could have dual LED lamps set up in a similar way.

On Sun, 15 Jul 2018 08:54:08 +0000 (UTC), you wrote:

I made a fixture years ago for working under the car at night. Three 150W bulbs in ceramic bases. Not only could I see everything, but it warmed up the carport in the winter!
CFLs are terrible. I do have some that have lasted a while, but most last about a year. I have incandescents that I haven't changed in ten+ years. One in a hallway is about 20 years old and still kicking.

The failure mechanism in an incandescent light is mainly related to
filament thinning as the tungsten evaporates slowly and is deposited
on the inside of the glass bulb. Eventually, the inrush current gets
that small higher resistance point up to where the filament just plain
melts.

For incandescents, the lifetime is related to the rated voltage to
applied voltage ratio. 10% more voltage, from what I've heard,
results in almost 1/10 the lifetime. 10% less, and you have a very
long life bulb. For those with choices, and 120 volts household (mine
is 122 to 123), use a 130 volt bulb to get very long life.

Now for CCFL and LEDS, well, no filament, so the failure mechanism (at
least completely for LEDS) is component failure generally due to
temperature (I ignore voltage spikes here). Some of the LED lamps get
rather hot, depending on whether the LED or the control electronics is
the problem heat source. We know what that does to the electronics.
Cheaply made is also a factor, of course. Anything in the commodity
market is generally made for lowest cost to manufacture traded off
against an acceptable failure/return rate.

There are carbon filament light bulbs (low temperature) that have been
operating for over fifty years. I have a fiber optics light source
for a microscope that has been working for several years (not
continuous), and is permanently set on the "LOW" setting.

Harvey

With incandescent bulbs you could put a diode in series and it would
last almost forever.
Efficiency was probably really crappy, but it still gave reasonable
(if a bit flickery) light output.

I've run such modified lights for many years, and I have even read
that you could buy a coin shaped diode insert in the US for just this
purpose.
No need to mention what too much of such nonsense would do to nearby
transformers.

Now for CCFL and LEDS, well, no filament, so the failure mechanism (at
least completely for LEDS) is component failure generally due to
temperature (I ignore voltage spikes here). Some of the LED lamps get
rather hot, depending on whether the LED or the control electronics is
the problem heat source. We know what that does to the electronics.
Cheaply made is also a factor, of course. Anything in the commodity
market is generally made for lowest cost to manufacture traded off
against an acceptable failure/return rate.

From: Bert Haskins <bhaskins@...>
Sent: Jul 15, 2018 9:09 AM
To: [email protected]
Subject: Re: [TekScopes] Stopping Lights from Strobing

On my solder station bench I had a drafting lamp with two 20 w tubes
that were a real pita.
I really liked the fixture so I replaced the tubes with dual row led
strips powered by a adjustable 12v smps.
Later I added a dimmer.
This ended up being just about all anyone could ask for, just the right
amount of light positioned just where you want it.

There is much less glare because the light comes from so many points.

These strips can be very versatile, they can be cut and resoldered for
use on 12, 24, 36... volts all the way up to (rectified) 120 AC.

I can furnish pictures upon request.

-- Bert

On 7/14/2018 11:29 PM, Michael A. Terrell wrote:

LEDs don't flicker when fed with clean, filtered DC. The light fixture in my bedroom has three LED bulbs under the ceiling fan and they don't flicker under normal usage. Just before they fail, I have had some start to flash at irregular intervals. All of the LED lamps I've see tell you not to operate them base up, but the only sockets that are base down seem to be table lamps and some outside lamps. I first installed some puny 1.5W LED lamps at the gateposts for my driveway. They were still working when I replaced them with some 7 watt bulbs. In total, there have been LED lamps there for over 15 years without a failure but it is cool when they are on. I've had two failures in two years in my bedroom where they started to flash, then they died.

At least where I am now near St. Louis, voltage spikes kill
incandescent, LED, and CFL bulbs about equally with a half life of
about half a year so less expensive incandescent bulbs (or passive
ballasted linear fluorescent bulbs) are the most economical by far.

At least in my experience, trying to return failed LED bulbs under
warranty is a waste of effort.

On Sun, 15 Jul 2018 11:08:39 -0400, you wrote:

Now for CCFL and LEDS, well, no filament, so the failure mechanism (at
least completely for LEDS) is component failure generally due to
temperature (I ignore voltage spikes here). Some of the LED lamps get
rather hot, depending on whether the LED or the control electronics is
the problem heat source. We know what that does to the electronics.
Cheaply made is also a factor, of course. Anything in the commodity
market is generally made for lowest cost to manufacture traded off
against an acceptable failure/return rate.

So far I have not had great luck with LED replacement bulbs built by CREE sold by one of the big box hardware stores. I used to send them back and get replacements? under warranty but as David says when you figure in the value of your time at the current lower prices it is not worth the effort. I took one of the 100W (equivalents) by Cree apart and found an amazing amount of engineering, There is a three terminal device in there, at least a dozen SMT resistors & diodes , a whopping big 33uf/350V electrolytic and a couple of dipped leaded silver micas, a small transformer even. Their is a tear down review of the 60W version here.

At least where I am now near St. Louis, voltage spikes kill
incandescent, LED, and CFL bulbs about equally with a half life of
about half a year so less expensive incandescent bulbs (or passive
ballasted linear fluorescent bulbs) are the most economical by far.

At least in my experience, trying to return failed LED bulbs under
warranty is a waste of effort.

On Sun, 15 Jul 2018 11:08:39 -0400, you wrote:

Now for CCFL and LEDS, well, no filament, so the failure mechanism (at
least completely for LEDS) is component failure generally due to
temperature (I ignore voltage spikes here).? Some of the LED lamps get
rather hot, depending on whether the LED or the control electronics is
the problem heat source.? We know what that does to the electronics.
Cheaply made is also a factor, of course.? Anything in the commodity
market is generally made for lowest cost to manufacture traded off
against an acceptable failure/return rate.

From: Artekmedia <manuals@...>
Sent: Jul 15, 2018 3:08 PM
To: [email protected]
Subject: Re: [TekScopes] Stopping Lights from Strobing

So far I have not had great luck with LED replacement bulbs built by
CREE sold by one of the big box hardware stores. I used to send them
back and get replacements? under warranty but as David says when you
figure in the value of your time at the current lower prices it is not
worth the effort. I took one of the 100W (equivalents) by Cree apart and
found an amazing amount of engineering, There is a three terminal device
in there, at least a dozen SMT resistors & diodes , a whopping big
33uf/350V electrolytic and a couple of dipped leaded silver micas, a
small transformer even. Their is a tear down review of the 60W version
here.



I no longer buy the CREE versions since I have had at least 1/2 dozen
failures in the first two years of use

I've had quite a few failures of the Cree bulbs also.? They are easy to exchange here though,? just bring 'em to Home Despot and trade them for new ones.? I haven't even had to show a receipt. I pulled one apart as well to check the build quality.? Looked pretty solid to me,? haven't bothered to trace down what failed in the dead ones though.
--Eric

Dave, I've had over a year's use form some I bought at Dollar Tree. They are on almost 24/7 and no failures so far. Due to my health, I leave them on while I'm sleeping so that I don't fall out of bed trying to find the table lamp.
Michael A. Terrell