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Comment by MrBuddyCasino | Hacker News Reader

LEDs just got more and more efficient. Even driving them with tiny currents produces bright light nowadays. I suspect once the efficiency increases stop, manufacturers will adapt and their engineers settle on limiting resistor values that are actually appropriate.

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So... there's these great things called data sheets, and they tell you how much current to run through your LED to yield a specific brightness level. Then you throw it into this bad boy here for instance [1]. You still have to do this to validate your design for every part picked.

It's like saying CPUs are getting more efficient, you know, so let's just run way too much voltage through them and hope for the best, and when the industry runs out of efficiency gains we can revisit it. Sure it's hotter than the devils nutsack. It'll be fine.

Efficiency gains are totally irrelevant to this conversation. It's designers who didn't read their data sheets, didn't care, or only tested their product in bright light. No excuse.

For an example datasheet check out [2], the luminous intensity vs. forward current graph is on page 7.

[1] http://led.linear1.org/1led.wiz

[2] http://www1.futureelectronics.com/doc/EVERLIGHT%C2%A0/334-15...

Blue LEDs are basically inappropriate for any purpose where they might be on at night. Making them dimmer doesn't fix the basic problem.

Use an orange or red light instead.

As a Red/Green color blind person I LOVE blue leds. They have mostly replaced the stupid Red/Green off/on indicator that I can't tell the difference between.

Now if only stop lights changed to "blue means go" we would live in a sane world. Picking two colors to mean opposite things (in life and death situations) that 5% of men can't tell the difference between is just a bit silly.

A simple solution for traffic lights would be to change the shape of stop lights to an octagon (matching the stop sign). This would be easy now they aren't a single bulb. Could also change the amber light to a triangle.

Emergency, Fire and Police flashers are mostly blue by convention. Fire, not as much, unless volunteer.

Beyond that, I've always found green lights to be fundamentally, much brighter than any red lights. Tail lights and traffic lights don't shine through bedroom windows nearly as much as when traffic lights turn green. You can see the same effect in black and white photography, but then again, not all traffic systems are the same intensity.

I have a high powered LED flashlight, with a red low-light option, and I find the red LED nearly unusable. I think red, though, is usually a dimmer color than green, when it comes to lighting in the additive color model, and lighting elements.

It's reflective colors that present much less distinguishable differences.

The human eye is more sensitive to green light, so it's not a case of red being dimmer, it's just how your eyes see them.

Traffic light manufacturers are shifting more to the blue end of the spectrum on the "go" light for this very reason.

I've noticed that myself (especially if there's a gas station nearby with a green-LED price sign). The green traffic light is, at least to my eyes, noticeably blue-green/aquamarine, where the gas station sign is emerald green.

LEDs just got more and more efficient. Even driving them with tiny currents produces bright light nowadays.

Yes. A flashlight today is one chip LED and a "do not stare into beam" warning.

Or, you know, you can just PWM them rather than having them going at full blast.

PWM resources can be quite scarce or overkill for a constant brightness level, just pick the right current limiting resistor, it's embedded design 101. Heck, it's your first-year electrical engineering class.

It's not hard to PWM by hand; it takes next to no resources.

Current limiting resistors don't really do great at lower strength; LEDs have far from linear responses and it's very constrained at the lower end that you want.

Source: wrote embedded firmware for close to a decade.

Thanks for that! I'll keep that in mind. I'm largely self-taught in embedded. Curious what you mean by PWM by hand.

> Curious what you mean by PWM by hand.

Have a timer that is some function of your PWM frequency, and manually toggle the GPIO line in the timer interrupt.

You can do it in a super loop too if you don't care about power consumption.

You don't need a whole pwm for a constant brightness reduction. The pulse width never has to change, which is the main feature of pwms.

which another large chunk of manufacturers messes up by choosing to low a frequency and not adding a filter, so now you see the flicker as soon as your eyes move...

Sure, you can screw up any scheme, regardless of how easy it is to do right.

Interestingly, when manipulating a led strip you can see light produced by voltage differences between your hands.

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