At what frequency does the human eye notice flicker?

walkintothelight, Thank you for the insight. I will have re-read my own questions because the flash is exactly how this conversation was started I thought. Or that is at least the concept I was trying to convey. let me check

Well, just keep in mind that “500 lumens using PWM” looks an awful lot like “500 lumens using constant current”. So, at least at the PWM frequencies that are typically used, our brains are not fooled into seeing anything more.

I tend to think that by the time PWM is showing us more (by slowing the rate), the flickering would be getting very annoying. Kind of like a strobe in a night club.

As noted earlier, flicker fusion can’t be specified generally for use in an equation — it’s specific to any one individual/health/age
https://www.google.com/search?q=flicker+fusion+aging+variation

And PWM isn’t the theoretically pure square waves — even if that’s the intent, there’s some noise up and down. They can be sawtooth pulses, etc.

And each phosphor used in the emitter has its own persistence.

Specify those and build one, and you might be able to craft an equation — after empirically determining the values that come out of the circuit, and the phosphors, and the flicker rate perceived by the subject.

This is why cheap drivers use visible (low-rate) PWM, and why better drivers, if they use PWM, use a much higher frequency, to stay well out of the, er, gray zone where some people will see it.

Building a light with say three cheap low-rate-PWM drivers, each somehow coordinated with the others to keep their notches from lining up, might theoretically work. But egad.

Now remember, I’m some guy on the Internets and know nothing about this stuff, so you may find better advice from someone else.

I think I have read somewhere that in this situation the light with the PWM will look brighter.

Source?

Because, I’ve never seen PWM described that way. I think if it really did fool our eyes to give increased sensitivity, it would be much more popular and marketed heavily. And, efficiency ratings (on lower levels where PWM is used), would be much better than they are when tested. Granted, testing equipment wouldn’t be fooled, but I’ve never noticed that a 100 lumen PWM light lasts any longer than a 100 lumen constant-current light (it’s usually the opposite).

Okay I really like the conversation this has brought about. Everyone seems to have a valid point in some regard or another.

My point is this. If a flash of light lasts a known amount of time and is quantifiable in terms of brightness, temperature, current draw and is repeatable at lets say 500Mhz frequency, does the millisecond timing provide enough lapse for the LED to recover to cycle EXACTLY the same. YES because we haven’t put a limit on the millisecond recovery value.

Again, follow me on this: We all agree that the luminous output of an LED begins to diminish within milliseconds after being energized and reaching its apex output. That is the holy grail of LED performance. That single measure of time when an LED gives all it can. It is at that point the most efficient.

The performance curve.

Now explain to me that if an LED is on and off an equal amount of time during lets say a 1 minute frame at a rate 30 times per second that after 1 minute an equal amount of energy has been consumed from this arrangement as opposed to an LED that was provided constant current during the same. It may not use exactly half as much energy but indeed significantly less.

But this isnt about energy, this is about achieving maximum luminous output.

energy efficiency is a bonus.

Btw, constant current indeed operates in pulses. All electrical current does. Hertz….its how we measure it.

I’m only replying to this part.

WHAT?

No.

So tell us what hertz your AC batteries operate at.

Again, I don’t think you’re going to see that in a real experiment. In reality, PWM has demonstrated itself to be less efficient than constant current. I don’t think there’s a special frequency that changes that. You haven’t given any plausible explanation why.

No, direct current does not operate in pulses. Alternating current is probably what you’re thinking of.

Earlier in your OP it was about minimal temperature and maximum efficiency.
But now that doesn’t matter because it’s about max luminous flux. Right?

And suddenly your flashlights operate on alternating current.
Are you trolling?

Did you even read that PWM is less efficient than Constant current in the quote I posted by Wight?

It doesn’t sound like he’s trolling. He’s putting in too much work for that.

I think he sounds more like someone trying to come up with a perpetual motion/energy design. That is, there’s no way to make it work, but some people won’t let that dissuade them.

I think(?) I understand what dehc111 is getting at.

Hypotheticals:

Yes we know that an LED is not at it’s most efficient when being pulsed at 6amps 50% cycle. 3amp CC is more efficient.

But let’s say the peak efficiency is at 2amps.

We could pulse 2amps at 50% cycle (net draw of 1amp) and in a perfect world it would be more efficient than running a constant current at 1amp.

The problem being that the pulse are not instant on/offs they are ramped with the LED not being as efficient on those ramps.

Am I getting both sides to an extent?

I agree that I think this is a fundamentally flawed venture.

You could easily calculate that if you want 6000 lumens, and your emitter does 800 lumens at it’s most efficient point, how many emitters and how much power you would need. No problem. But you still want to go CC, not pulsed.

The problem is that if LEDs have an efficiency peak, it’s at an extremely low current (at least for Cree). Take any led from http://pct.cree.com/dt/index.html , I’m pretty sure that for all tested currents the efficiency lm/W decreases as the current increases. Also the efficiency lm/A (Current), which would be useful if you use a linear driver, seems to decrease monotonically as the current increases. I believe that most if not all leds follow the same pattern.

Of no practical use, but … interesting

Also a very misleading title. All they’re doing is using heat from the environment to power the LED. It’s not greater than 100% efficiency.

LMAO AC batteries…. good one…… that made me lol for real.

I apologize as I didnt mean to abandon the topic…… At all. I am trying to find someone to understand where I am trying to take this. Between my poor vocabulary and marginal communication skills on the topic, slight ADHD ADD XYZ or wut ever i suffer from, I sincerely appreciate your attention. I assure you I am not trolling or the like. My time is as valuable as yours and in the end we will all have gained something from this.

Okay. All current does pulse. Let me define pulse I suppose. Pulsation is patterned vibration < down and dirty definition.

Matter of fact all matter in the known universe pulses. It is called resonate frequency. I wont go into an atomic theory here but this is a generally accepted concept.

Now that we have established that in fact DC current pulses lets explore managing or controlling this pulsation.

To keep the conversation focused I am trying to achieve maximum luminous output sustained. secondary would be efficiency and third heat.
I am not interested in perpetual energy or any far right experimental b.s. of the kind. (at least not in this thread on this forum)

Back to the equation… You think it has no relevance ? The values are not associative ? Please help me define which values are then.

Low current as compared to what?

Low current as compared to higher current, empirically, e.g.

See also

Okay but I don’t what the red line is representing? or the dashed line.

Good link Hank! Thank you.

The article discusses modifying the waveform to compensate for an AC circuit.

This is interesting because the AC mimics the on/off pwm this thread is exploring. What I find even more interesting about that article was the proposed change from 120mhz to 150mhz the EPA tried to mandate
because of a known negative effects or sensitivities that humans experience at ~ 120mhz.

Weaponize an LED’s in this frequency range? Isnt that the same frequency (120 mhz) that LED T.V.’s utilize for rendering high definition 1080P?

Okay that will make a great topic for another thread!!!

I knew there was some kind of relative association that exists.

Okay I need to think on this more so I can construct my questions from another perspective.