Author Topic: 24000 lumens of workshop lighting  (Read 710 times)

24000 lumens of workshop lighting
« on: July 13, 2020, 04:27:57 pm »
Just scrapped the flourescent batten fittings for four of these luminares.
https://cpc.farnell.com/v-tac/669-vt-8-50/grill-fitting-50w-led-150cm-6400k/dp/LA07402 @ £23 each they  give a lot of lumens per £.
With the full 200W 24,000 lumens output the Operating Theatre Workshop is so well lit that I can now solder without my +3 dioptre close up glasses. :-)
Just out of interest I  wondered about flicker frequency - A 2N3906 lost its tin hat and got wired up onna bit of veroboard as a lashup phototransistor. PP3 supply biased on with a fewmegs of base resistor - good 10KHz squarewave out using a test LED light source.
'scope showed a 100Hz raised sinewave from the luminare 620-1150 mV pk-pk. dark collector DC Voltage was 330mV. May post some photos of the illuminations after a tidy up.

Kim

  • Timelord
Re: 24000 lumens of workshop lighting
« Reply #1 on: July 13, 2020, 04:59:23 pm »
Just out of interest I  wondered about flicker frequency - A 2N3906 lost its tin hat and got wired up onna bit of veroboard as a lashup phototransistor. PP3 supply biased on with a fewmegs of base resistor - good 10KHz squarewave out using a test LED light source.
'scope showed a 100Hz raised sinewave from the luminare 620-1150 mV pk-pk. dark collector DC Voltage was 330mV. May post some photos of the illuminations after a tidy up.

I really wish they'd include this spec in the datasheet.  That would give barakta multiple images every time she moves her head, and the stonking migraine would follow soon after.
Careful, Kim. Your sarcasm's showing...

Re: 24000 lumens of workshop lighting
« Reply #2 on: July 13, 2020, 05:57:25 pm »
I realized that could still be a problem for some.  It's not bad either as these things go, between approx 30 and 100% sinusoidally rather than the expected 0-100% raised cosine.I tried the hand wave finger strobe test first and could not observe any effect.

Kim

  • Timelord
Re: 24000 lumens of workshop lighting
« Reply #3 on: July 13, 2020, 06:01:31 pm »
Yeah, barakta's more sensitive than most people, because her eyes don't track horizontally.  She moves her head and sees motion blur (or stroboscopic effects, under flickering lighting) the way a long-exposure camera would.  She can see the 100Hz ripple on mains-powered tungsten lamps, for example, which I certainly can't.
Careful, Kim. Your sarcasm's showing...

Re: 24000 lumens of workshop lighting
« Reply #4 on: July 13, 2020, 06:12:11 pm »
That's amazing, the thermal inertia must Shirley mean it's only a certain percentage of the total light output..

Kim

  • Timelord
Re: 24000 lumens of workshop lighting
« Reply #5 on: July 13, 2020, 06:20:33 pm »
I think the CFL in our kitchen has something of the order of a 15% ripple (not a pure sine wave) on it, and she moans about that.  (It's the least bad one I can find that's decently bright.)

High-contrast edges exacerbate the effect, so she'll struggle with stripey decor too.

The really impressive thing is how disinterested the medics are about the whole thing "some lighting causes some people to get migraine" is their level, and even orthoptics don't really care beyond her double vision (everything outside a 15° central field).  We've had to work a lot of this stuff out from first principles, after several of those "What do you mean you can move your head without seeing a blur?" conversations.
Careful, Kim. Your sarcasm's showing...

Re: 24000 lumens of workshop lighting
« Reply #6 on: July 13, 2020, 06:42:07 pm »
That's amazing, the thermal inertia must Shirley mean it's only a certain percentage of the total light output..
The light comes from LEDs. They emit light while cold and the response time is in nanoseconds. Lots of badly designed LED lights have huge modulation. VW even managed to modulate the LEDs at 100 Hz on car tail lights where the power source was DC.
Quote from: Kim
Paging Diver300.  Diver300 to the GSM Trimphone, please...

Re: 24000 lumens of workshop lighting
« Reply #7 on: July 13, 2020, 07:29:00 pm »
Correction:  at that point I was commenting about tungsten filament lamps. ∆∆ absolutely right about LEDs night riding in a group with pedals and road surface strobing away is horrible. Upthead these light I am using are good for most people.

Kim

  • Timelord
Re: 24000 lumens of workshop lighting
« Reply #8 on: July 13, 2020, 07:30:58 pm »
It appears that the film people have problems with it...

https://cinematography.net/edited-pages/Tungsten-lamp-flicker-at-96-fps.htm  (ignore the mid-thread digression into leftpondian centre-tapped mains supplies)

Sounds like it depends on the filament design.  The last one barakta objected to was a mains-voltage 250W halogen, I haven't compared it to a bog standard 40W lamp, or indeed 12V halogen via a magnetic transformer.  (IIRC 12V is the sweet spot for filament mechanical sturdiness, so might correlate with a bit more thermal mass?)

It's academic, as we've done away with tungsten on efficiency grounds.  (Though I note that many photosensitive migraine sufferers are sticking to tungsten lighting to avoid triggers, which may be unwise.)
Careful, Kim. Your sarcasm's showing...

Re: 24000 lumens of workshop lighting
« Reply #9 on: July 13, 2020, 07:36:12 pm »
Just scrapped the flourescent batten fittings for four of these luminares.
https://cpc.farnell.com/v-tac/669-vt-8-50/grill-fitting-50w-led-150cm-6400k/dp/LA07402 @ £23 each they  give a lot of lumens per £.
With the full 200W 24,000 lumens output the Operating Theatre Workshop is so well lit that I can now solder without my +3 dioptre close up glasses. :-)
Just out of interest I  wondered about flicker frequency - A 2N3906 lost its tin hat and got wired up onna bit of veroboard as a lashup phototransistor. PP3 supply biased on with a fewmegs of base resistor - good 10KHz squarewave out using a test LED light source.
'scope showed a 100Hz raised sinewave from the luminare 620-1150 mV pk-pk. dark collector DC Voltage was 330mV. May post some photos of the illuminations after a tidy up.
The 50 W ones have a power factor of >0.9. That means that the current taken is broadly sinusoidal, like the mains supply. The light has to take current when the voltage is well below the peak voltage in order to get a good power factor. (The lower power lights in that range don't have to bother doing that, and as a result they have much worse power factors)

One way of getting a good power factor is to have several strings of LEDs, with a circuit to turn on different numbers of strings depending on the instantaneous voltage. Here is a typical control IC that claims >0.9 pf:-https://docplayer.net/28993664-Sw5909-datasheet-ac-direct-control-ic-for-led-lighting-rev-0-1-jul-26-rev-0-0-silicon-works-co-ltd-1.html

That circuit runs without an energy storage capacitor, and the current taken from the supply is vaguely sinusoidal and in phase with the voltage, so the light output should also be sinusoidal at twice the mains frequency, which is what you found.

I've got some 22 W PIR-controlled outside lights that use that IC, and the flicker was very bad. I improved it by putting a capacitor across the LED string that is on all the time. It's better, but I can still see it a bit, and I wouldn't work under them even after the improvements, but they'll do for taking the bins out.

It wouldn't work to put capacitors across the other strings as they are shorted out during parts of the cycle, so diodes would have to be added to stop capacitors being discharged each half cycle. The IC was on the same aluminium PCB as the LEDs, so modifications like that are a pain.

I tried putting a big capacitor directly across the rectifier, and there was no flicker, but the IC went into thermal shutdown after a couple of seconds and then cycled on and off every second or so after that.

Quote from: Kim
Paging Diver300.  Diver300 to the GSM Trimphone, please...

Kim

  • Timelord
Re: 24000 lumens of workshop lighting
« Reply #10 on: July 13, 2020, 07:43:09 pm »
One way of getting a good power factor is to have several strings of LEDs, with a circuit to turn on different numbers of strings depending on the instantaneous voltage. Here is a typical control IC that claims >0.9 pf:-https://docplayer.net/28993664-Sw5909-datasheet-ac-direct-control-ic-for-led-lighting-rev-0-1-jul-26-rev-0-0-silicon-works-co-ltd-1.html

That's quite clever.  In a yes-but-it-still-flickers kind of way.

In my more tragic moments, I've wondered about the practicality of feeding lighting circuits with mains-voltage DC, so you could use chinesium LED lamps with impunity.  Then I remember the capacitive droppers...
Careful, Kim. Your sarcasm's showing...

Re: 24000 lumens of workshop lighting
« Reply #11 on: July 13, 2020, 07:46:20 pm »
It appears that the film people have problems with it...

https://cinematography.net/edited-pages/Tungsten-lamp-flicker-at-96-fps.htm  (ignore the mid-thread digression into leftpondian centre-tapped mains supplies)

Sounds like it depends on the filament design.  The last one barakta objected to was a mains-voltage 250W halogen, I haven't compared it to a bog standard 40W lamp, or indeed 12V halogen via a magnetic transformer.  (IIRC 12V is the sweet spot for filament mechanical sturdiness, so might correlate with a bit more thermal mass?)

It's academic, as we've done away with tungsten on efficiency grounds.  (Though I note that many photosensitive migraine sufferers are sticking to tungsten lighting to avoid triggers, which may be unwise.)
I've seen strobing on fan when lit with a 40W 230V 50 Hz tungsten lightbulb. It wasn't bad, in that it didn't make the fan look stationary, it just meant that the bolts on the fan hub could be sort of seen with it running. When lit with a torch the bolts were a complete blur.

At school, the physics master demonstrated 1kHz modulation of light from tiny light bulb.

Also at school, the stage lighting had some 1 kW tungsten halogen light bulbs. They appeared to have a big time constant, in that the red glow from the cooling filament took about 2 seconds to vanish. However, the heat loss mechanism would have been different at white-hot temperatures than at red-hot temperatures.
Quote from: Kim
Paging Diver300.  Diver300 to the GSM Trimphone, please...

Re: 24000 lumens of workshop lighting
« Reply #12 on: July 13, 2020, 07:47:26 pm »
 I  think the luminaries I am using must therefore have some energy storage on the low voltage string as divers modified lamp

Kim

  • Timelord
Re: 24000 lumens of workshop lighting
« Reply #13 on: July 13, 2020, 07:55:44 pm »
Also at school, the stage lighting had some 1 kW tungsten halogen light bulbs. They appeared to have a big time constant, in that the red glow from the cooling filament took about 2 seconds to vanish. However, the heat loss mechanism would have been different at white-hot temperatures than at red-hot temperatures.

Because of this stage lighting dimmers usually have a (independent of the control system) pre-heat setting to keep the filament at just-below-a-visible-glow temperature, in order to speed their response to dimming up (down is usually less of a problem, because eyes are also slow to react) and reduce thermal shock.  Which (along with TRIACs that aren't very good at switching off when lightly loaded) can lead to Hilarious Consequences if you try to use them to control small loads[1].

There can be a noticeable difference in response between different designs of tungsten halogen lamp when dimmed quickly with the same signal, especially if you turn the pre-heat off.


[1] Hence 'ghost load' (a lamp connected in parallel out of view[2]) - not to be confused with 'ghost light' (a lamp left on so the first person in doesn't trip over trying to find the switch for the work lights).
[2] Something that was routine in the days of resistive dimmers.
Careful, Kim. Your sarcasm's showing...

Re: 24000 lumens of workshop lighting
« Reply #14 on: July 13, 2020, 08:04:19 pm »
One way of getting a good power factor is to have several strings of LEDs, with a circuit to turn on different numbers of strings depending on the instantaneous voltage. Here is a typical control IC that claims >0.9 pf:-https://docplayer.net/28993664-Sw5909-datasheet-ac-direct-control-ic-for-led-lighting-rev-0-1-jul-26-rev-0-0-silicon-works-co-ltd-1.html

That's quite clever.  In a yes-but-it-still-flickers kind of way.

In my more tragic moments, I've wondered about the practicality of feeding lighting circuits with mains-voltage DC, so you could use chinesium LED lights with impunity.  Then I remember the capacitive droppers...

In my more tragic moments, I've actually done that, having chosen the bulbs with care.

Some chinesium LED lights have a mains rectifier, followed by a too-small electrolytic capacitor, and then a switch-mode supply. The too-small capacitor either leads to residual flicker, or overheats and dries up and causes the switch-mode supply to shut down, and restart and so on. An external rectifier and capacitor allows a generous capacitor rating (sometimes so generous that there is a slight delay from flicking the switch to the light output stopping). It can also revive bulbs that are dead due to failed too-small capacitor without needing to open them up.

Lights with capacitive droppers often have no smoothing, or smoothing that uses the stock of too-small electrolytics that the bulb manufacturers have. I've de-flickered those by adding significantly larger capacitors, but that needs them to be opened up.

Quite a few LED light bulbs have the electronics in the base, and a flat aluminium circuit board that is across the top of the opaque white part, and the translucent part is completely empty. The translucent part can often be removed by just pulling, leaving a working bulb. Often the + and - are marked, and the voltage can be measured, and a suitable capacitor can be added. A large electrolytic capacitor sticking up in the middle of the circuit board is surprisingly difficult to see when the translucent part is back in place. Lights fixed like that may take a moment to turn on as the capacitor charges, and may dim slowly when turned off. I may have over-done the capacitor size in places.

Both types of modification will be less flicker at the expense of worse power factor.
Quote from: Kim
Paging Diver300.  Diver300 to the GSM Trimphone, please...

Re: 24000 lumens of workshop lighting
« Reply #15 on: July 13, 2020, 08:17:22 pm »
Which (along with TRIACs that aren't very good at switching off when lightly loaded) can lead to Hilarious Consequences if you try to use them to control small loads.
The capacitance between wires can lead to mains powered LED lights glowing when turned off.

The ones with mains voltage rectifiers followed by an SMPS can flash every now and then, when the capacitor is charged. Capacative dropper ones usually glow.

I guess it is worse with two-way switched lights, where the cables will have live and switched live adjacent, without an earth wire in between.
Quote from: Kim
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Kim

  • Timelord
Re: 24000 lumens of workshop lighting
« Reply #16 on: July 13, 2020, 08:28:57 pm »
Yeah I've seen that happen, too.

Also encountered the inverse effect at Dr Biggles's house: lamps that would flick off for a few mains cycles in order to measure the ambient brightness to work out whether they were supposed to be on or not.  Probably okay in an outside light, but bloody annoying indoors.  In the interests of sanity, I relocated them to the box in the cupboard and replaced them with Yet More Halogens[1].


[1] Not content with a career in aviation, he's always willing to do his bit for climate change, especially if it involves spending more money.
Careful, Kim. Your sarcasm's showing...

Re: 24000 lumens of workshop lighting
« Reply #17 on: July 13, 2020, 08:31:35 pm »
Can you not drive them with a linear power supply that provides a constant DC voltage?
I think you'll find it's a bit more complicated than that.

Re: 24000 lumens of workshop lighting
« Reply #18 on: July 13, 2020, 08:42:55 pm »
I'm not sure you exactly mean 'linear' that's the type of PSU with a wound iorn cored transformer, and regulator transistors on heatsinks. But coming back to my 50 Watt led luminaries  they would each  require the type of switching PSU brick that is connected to a laptop. Not going to buy  that plus the rest for £23 from CPC.

Re: 24000 lumens of workshop lighting
« Reply #19 on: July 13, 2020, 09:17:25 pm »
I meant not a switch mode power supply so it wouldn't be noisy with the remains of the mains cycle.
It was meant for Kim really as you aren't bothered by the 100Hz flicker.
I think you'll find it's a bit more complicated than that.

Re: 24000 lumens of workshop lighting
« Reply #20 on: July 13, 2020, 09:24:19 pm »
'pologies, still I think Kim has molishing molished.

Kim

  • Timelord
Re: 24000 lumens of workshop lighting
« Reply #21 on: July 13, 2020, 09:40:54 pm »
Most of our room lighting is now based on my own LED drivers, which take DC from a switching power supply, and then do current-dimming (via a high-frequency switching regulator) of the LED.  Fully dimmable, zero perceptible flicker, very little (>200kHz) ripple measurable at the LED with an oscilloscope, and barakta-approved.

I found some 7W LED lamps from Wilko that do a proper job (as long as the mains voltage stays in spec, see rants passim) of smoothing, which is fine for the bathroom.  We also found some (DC-powered, via a wall-wart) desk lamps that PWM dim in the 50kHz range, which barakta can't percieve.  It's just the kitchen that's a bit of a compromise, as we're stuck with a big bright CFL in the landlord's crappy fitting in order to see the muck amongst the dinge.

Then there's the challenge of display devices.  Most computer LCD displays PWM dim their backlight in the 200-400Hz range, which is headache-inducing.  Multiplexed LED displays exhibit all sorts of exciting artifacts, but they're less of a problem as barakta doesn't spend much time staring at them.  A recent annoyance is our new kettle, which has a nice bright BLUE! LED ring of yes-I'm-on-ness (which is more useful when you can't hear it boiling), but appears to be driven by a half-wave rectifier.  I need to dig the security bits out and see how much space there is for modifications...
Careful, Kim. Your sarcasm's showing...

Re: 24000 lumens of workshop lighting
« Reply #22 on: July 13, 2020, 11:41:38 pm »
A recent annoyance is our new kettle, which has a nice bright BLUE! LED ring of yes-I'm-on-ness (which is more useful when you can't hear it boiling), but appears to be driven by a half-wave rectifier.
These https://www.mobilefun.co.uk/quirky-pivot-power-flexible-5-plug-power-adapter-white-39661 had four white LEDs run from half-wave rectified mains.

What was inexplicable was that the four LEDs were in two strings, so taking twice the power from the mains that would have been taken with all four in series.

I put all four in series, and added a smoothing capacitor. The half-wave rectification remained, as it was easier to fit twice the size of capacitance than to rearrange the circuit even more.
Quote from: Kim
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Kim

  • Timelord
Re: 24000 lumens of workshop lighting
« Reply #23 on: July 13, 2020, 11:48:47 pm »
That's presumably what they mean by 'quirky' (not generally my first priority in power distribution).
Careful, Kim. Your sarcasm's showing...

Re: 24000 lumens of workshop lighting
« Reply #24 on: July 13, 2020, 11:56:35 pm »
Maybe fault tolerance - I presume the LED's indicate 'Power ON'.  In my early days Marconi TV transmitter fault indicator lamps were normally  'ON' - so you could presume if OFF the lamp had burnt out or indeed there was a fault condition. We called it Marconi Logic.