DiY LED - Cree CXA3070

[uzerneims]

What drivers are powering each one? If you swap drivers does it makes lines on the Vero29?

Both are Chinese, both from ebay, one is DT-xxxx driver, other is LED DRIVER, haha...
Will try to switch

But i have only left other drivers, not V29's, will try to switch drivers...
Will try to turn on both, and see diff...

But should that change something in outcome?

 

[alesh]

Both are Chinese, both from ebay, one is DT-xxxx driver, other is LED DRIVER, haha...
Will try to switch

But i have only left other drivers, not V29's, will try to switch drivers...
Will try to turn on both, and see diff...

But should that change something in outcome?

Yes, you're gonna find whether there's something wrong with your driver or Vero.

 

[SupraSPL]

That is a good question. I came across some drivers that seem to flicker when the light is in my peripheral and I am moving. I tested the lux/W to see if it was some kind of PWM that might be harming efficiency but as far as I could tell there was no difference.

Some people complain it gives them migraines and dizziness, which I do not doubt, but I don't think the plants will care as long as it is not direct PWM dimming.

Many of our LED lit laptop screens and TVs are using direct PWM dimming which makes me dizzy when I move my eyes down the screen sometimes, so I keep it at full brightness and dim with gamma controls instead. You can see it in many new cars LED tail lights. They PWM dim during regular driving and go to full brightness when the driver presses the brake. Very annoying on the road and regrettable engineering IMO, they could have used constant current dimming that was PWM controlled instead, but it would probably have cost more.

 

[stardustsailor]

Actually ,thats the way switching power supplies do work .
They apply PWM to Input voltage in order to regulate it as output voltage .
Then the "dimmed " -output-voltage is being converted to DC from AC (in case of plug supplies ),through a "diode bridge " (rectifier )and capacitors(s) (for smoothing ) .

The constant current switching supplies ,constantly regulate the duty cycle of the PWM ,in order to regulate the voltage ,based on the -measured-resistance of the load ,in order to keep the current at a certain level / value.

Weird thing ,is that PWM has a frequency -at most cases- in the kHz region.
So ,normally the human vision can not detect that " flickering " ...
But with low quality power supplies ,I guess everything is possible..

Cheers.

 

[Doer]

I have a drill press, you can do it with a hand drill but it's hard to keep them straight

That is a good question. I came across some drivers that seem to flicker when the light is in my peripheral and I am moving. I tested the lux/W to see if it was some kind of PWM that might be harming efficiency but as far as I could tell there was no difference.

Some people complain it gives them migraines and dizziness, which I do not doubt, but I don't think the plants will care as long as it is not direct PWM dimming.

Many of our LED lit laptop screens and TVs are using direct PWM dimming which makes me dizzy when I move my eyes down the screen sometimes, so I keep it at full brightness and dim with gamma controls instead. You can see it in many new cars LED tail lights. They PWM dim during regular driving and go to full brightness when the driver presses the brake. Very annoying on the road and regrettable engineering IMO, they could have used constant current dimming that was PWM controlled instead, but it would probably have cost more.

Damn. I'll probably see it everywhere now. I had not noticed before. ...or have I.....?

 

[SupraSPL]

Actually ,thats the way switching power supplies do work .
They apply PWM to Input voltage in order to regulate it as output voltage .
Then the "dimmed " -output-voltage is being converted to DC from AC (in case of plug supplies ),through a "diode bridge " (rectifier )and capacitors(s) (for smoothing ) .

The constant current switching supplies ,constantly regulate the duty cycle of the PWM ,in order to regulate the voltage ,based on the -measured-resistance of the load ,in order to keep the current at a certain level / value.

Weird thing ,is that PWM has a frequency -at most cases- in the kHz region.
So ,normally the human vision can not detect that " flickering " ...
But with low quality power supplies ,I guess everything is possible..

Cheers.

There is a critical difference between direct PWM dimming and PWM controlled, constant current dimming. I am on the lookout for the type of drivers that run the LED at high current and simply flicker it on and off to achieve dimming. This reduces electrical consumption, light intensity and junction temp, but causes unnecessary loss of efficiency from current droop and can cause physiological problems.

The flicker I am referring to is repeatably noticeable to the human eye, although very slight, with this driver and this driver. I know the human eye cannot detect flicker in the kHz range, I expect this flicker must be in the 120Hz or lower range. No big deal but it is interesting.

Thankfully I cannot detect flicker on the LED laptop or TV screens, but you can check for it by viewing through a through a camera and see how flicker increases the more you dim it, and it goes away at full brightness. The high frequency flicker can have physiological effects in some people even if the eye cannot detect it directly. They can make screens and cars that can dim flicker free but most choose not to. I checked the screen on a pair of smartphones and they do not flicker when dimmed

LED MONITORS CAN CAUSE HEADACHES DUE TO FLICKER

 

[stardustsailor]

There is a critical difference between direct PWM dimming and PWM controlled, constant current dimming. I am on the lookout for the type of drivers that run the LED at high current and simply flicker it on and off to achieve dimming. This reduces electrical consumption, light intensity and junction temp, but causes unnecessary loss of efficiency from current droop and can cause physiological problems.

Well,as I've mentioned that is exactly the same thing.But if there's a critical difference that I'm not aware of ,please do take the time to explain it ..I'm always eager to learn new things .

The flicker I am referring to is repeatably noticeable to the human eye, although very slight, with this driver and this driver. I know the human eye cannot detect flicker in the kHz range, I expect this flicker must be in the 120Hz or lower range. No big deal but it is interesting.

Thankfully I cannot detect flicker on the LED laptop or TV screens, but you can check for it by viewing through a through a camera and see how flicker increases the more you dim it, and it goes away at full brightness. The high frequency flicker can have physiological effects in some people even if the eye cannot detect it directly. They can make screens and cars that can dim flicker free but most choose not to. I checked the screen on a pair of smartphones and they do not flicker when dimmed

LED MONITORS CAN CAUSE HEADACHES DUE TO FLICKER

Flickering at general ,no matter the type of source ,yes indeed can easily cause headaches and more than that actually.
Even epileptic seizures are listed on the "menu".Although kinda rare of a "meal" .

"The effects of flicker can range from decreased visual performance to non-specific malaise to the onset of some
forms of epilepsy."

http://www.essex.ac.uk/psychology/overlays/2010-195.pdf

Cheers.

 

[SupraSPL]

It is explained somewhat in the article I linked, direct PWM dimming literally flickers the light (at full current) to achieve dimming, rather than actually reducing the current to achieve dimming. We are not talking kHz but Hz, easily noticeable to the naked eye. To dim further, it just uses longer pauses, making the flicker even worse. That is a cheap and careless dimming method when the light is intended for human use.

I have a pair of 3.6V LED headlamps. One uses PWM dimming and the other uses constant current dimming. The PWM is literally un-useable when dimmed, anytime you move your head you can see everything flashing in your peripheral, just like many of the new car taillights I mentioned. The constant current dimmed headlamp is smooth even when dimmed to very low currents, no flickering whatsoever.

When it comes to AC, there is more to the story but the circuitry is over my head. Some cheap drivers create flicker even though they are not dimmed. Most cheap drivers do not flicker though.

 

[stardustsailor]

It is explained somewhat in the article I linked, direct PWM dimming literally flickers the light (at full current) to achieve dimming, rather than actually reducing the current to achieve dimming. We are not talking kHz but Hz, easily noticeable to the naked eye. To dim further, it just uses longer pauses, making the flicker even worse. That is a cheap and careless dimming method when the light is intended for human use.

I have a pair of 3.6V LED headlamps. One uses PWM dimming and the other uses constant current dimming. The PWM is literally un-useable when dimmed, anytime you move your head you can see everything flashing in your peripheral, just like many of the new car taillights I mentioned. The constant current dimmed headlamp is smooth even when dimmed to very low currents, no flickering whatsoever.

When it comes to AC, there is more to the story but the circuitry is over my head. Some cheap drivers create flicker even though they are not dimmed. Most cheap drivers do not flicker though.

Supra,allow me to be a hardcore fan and a true believer of the moto
" You get what you pay for ".
( Especially when living in this modern world of free-market capitalism...)
Anyway ...

Allow me to give you an example of what I'm talking about ....


^^^^^ Adjusted at " x1 " an oschilloscope probe was placed on a VERO 29 ....


^^^^^ The VERO 29 was driven by a Meanwell HLP-60H-42 driver (mains: 220 VAC,50 Hz,EU ).
At 1530 mA (open dim+ and dim- ) and with a horizontal DIV of 20 usec (every horizontal side of a square is 20 usec time DIV ) ,the voltage is ~37.5 VDC .( every vertical side of a square is 10 VDC ).Do you see any flickering ?
I do not .None whatsoever ...Absolutely none ...


^^^^ same as before ,but now the VERO is driven at ~ 350mA (dimmed via resistor between Dim+ & Dim -) .
Now, every horizontal DIV is 1 msec .Vf has dropped to about 34 and something Volts.Still,no flickering whatsoever .
NONE !

I've tried several frequencies and driving currents. None detectable flickering at the range 1 Hz- 1 MHz .
Absolutely none !

Let us see what happens with a 8mm plastic packaged 1 Watt LED and a cheap SATISLED CC driver .
(model LED-L1825W-A / http://www.satisled.com/constant-current-driver-for-1825pcs-1w-high-power-led-1825x1w-driver-waterproof_p559.html )


Probe installed as in previous case ...
And ....


Voltage DIV = 1 VDC Time DIV = 10 usec .
Led is driven at ~ 320 mA , with a VF close to +3 VDC .
Flickering is not detectable by human vision as it has a frequency of about 100 kHz ...
But it's there ..
With the driver having " noise " with Vp-p (peak to peak ) of more than 2 whole volts !!!
Still ,it can cause health issues like impairments in visual performance- maybe permanent under long term exposure -.

Cheers.

 

[Doer]

The days of yester-year. I used to carry an o-scope, to service calls.

Oh, if I only had her now. I would never curse her slightly dumpy appearance, like I did before. I would never again complian she is over weight and finicky. I don't care anymore, that she is hard to bring to resolution.

 

[Doer]

Now all I have is an arduino with Processor running an 0-scope UI.

 

[stardustsailor]

I bought this from e-bay ,imported from US.
The total price (shipping & customs included ) was about $120 .
It's from the early 80's ,from a Cali-based brand ,called " JDR Instruments " .

http://imagine41.com/jdr-instrument-model-2000-dual-channel-20-mhz-oscilloscope.html

Actually it was brand new ( meaning totally unused ) and
it came along with it's manual and with a pair of -good quality probes <=brand new ,with all the accessory tips & parts - ( Coline LTD ,Made in UK ).


Later, I found out that this o-scope it's just a re-branded piece of equipment .
Rather cheap and of low-quality "Made in Korea " crap.
Still,for the total price paid (o-scope,pair of probes,shipping & customs ) ,it does it's basic job.
You get what you pay for.I insist on that one ...
Now I'm after a digital o-scope of better quality than the current analog.
But it has to wait.
A thermal imaging camera comes first .

Cheers.

 

[Doer]

Yeah, I have software for digital, multichannel spectrum analysis. But, there is nothing like knob tweeking and a CRT analog look.

This is before my time even, what my dad used in the Air Force.

 

[LeanMcsheen]

I would never have guessed those beans were so old! must have been well stored eh?

 

[Doer]

There used to be an o-scope as a prize in some of the cans.

 

[SupraSPL]

Cool experiment SDS, unfortunately way over my head. I don't think you are suggesting that only cheap LEDs flicker, more that the cheap driver is more likely to flicker? I have some $0.70 drivers that do not flicker visibly. But these 2 drivers do, visibly to the human eye, even though they are not dimmed and it has something to do with its particular circuitry, related to the frequency of the AC mains apparently. It happens when driving any LED with this driver, including Veros. I don't know exactly why these drivers flicker and most do not, I was hoping you could tell us. Digikey has a good article about it from 2012
http://www.digikey.com/en/articles/techzone/2012/jul/characterizing-and-minimizing-led-flicker-in-lighting-applications

 

[SupraSPL]

In regard to DC powered LEDs, the difference between constant current and PWM dimming is strongly evident, such as the headlamp example I gave earlier. This headlamp and many others use PWM dimming and it is disturbing, unusable


This $10 unit uses constant current dimming rather than PWM dimming and it is perfectly steady, no flicker. I slap a Panasonic Li-Ion and XPL in there and wear it all day everyday

 

[Doer]

In regard to DC powered LEDs, the difference between constant current and PWM dimming is strongly evident, such as the headlamp example I gave earlier. This headlamp and many others use PWM dimming and it is disturbing, unusable
View attachment 3382339

This $10 unit uses constant current dimming rather than PWM dimming and it is perfectly steady, no flicker. I slap a Panasonic Li-Ion and XPL in there and wear it all day everyday
View attachment 3382340

1- the headphones are low volt DC

Could it be that you both are correct? I see that a lot.

I don't think Cheap is always linear with Price. For the10 dollar headphone they didn't cheap out with the driver. In cars taillights, who cares?

I recently built a little 5v switching power supply from an adafruit industries kit. I think it was a $8.00 kit. When I got done (test run for my new digital soldering station) I could see the little test LED flickering as soon as I fired it up. WHA??

So, I hook up my Ardunio o-scope sketch, and I was shocked. The duty cycle was so coarse, you could see the switch points on the LED and the noise amplitude was close to 10x.

So, you get what you pay for. And important companies like Panasonic cannot afford to over look detail even at a $10 price point. It is all trade offs. And any company that got to be Panasonic level cannot afford to trade any Good Name and Good Will.

That is how I see it.

 

[Doer]

I bought this from e-bay ,imported from US.
The total price (shipping & customs included ) was about $120 .
It's from the early 80's ,from a Cali-based brand ,called " JDR Instruments " .

http://imagine41.com/jdr-instrument-model-2000-dual-channel-20-mhz-oscilloscope.html

Actually it was brand new ( meaning totally unused ) and
it came along with it's manual and with a pair of -good quality probes <=brand new ,with all the accessory tips & parts - ( Coline LTD ,Made in UK ).
View attachment 3381743

Later, I found out that this o-scope it's just a re-branded piece of equipment .
Rather cheap and of low-quality "Made in Korea " crap.
Still,for the total price paid (o-scope,pair of probes,shipping & customs ) ,it does it's basic job.
You get what you pay for.I insist on that one ...
Now I'm after a digital o-scope of better quality than the current analog.
But it has to wait.
A thermal imaging camera comes first .

Cheers.

If you have an iPhone or Android, you already have a TIC. They have an app for that.

 

[Doer]

imperceptible flickering

Don't you hate that. It gets to me over time at work with the over head fluorescence.

We turn them off as much as we can and still don't trip the fire codes with the walk though inspections. We engineers are not good at follow suggestions from the pencil pushers.

"Oh," we say. " How about no light is better than flicker?" TRUMP.