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Blinking LED Indicators Shouldn’t Turn All The Way Off

Attentional noise reduction.
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(+7, -1)
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A lot of devices and products and technical gear have LED indicators. Sometimes these are static — on for something, off for lack of something. Sometimes they blink to indicate “activity”. The way they blink is an inversion of the ‘on’ logic, so that the light is on to indicate that the function is active or available or working, and to overload that single LED with another layer of information, it is momentarily turned off in a brief flash of nothingness, and back on. Thus, you have devices that will have a single LED or rows of single LEDs (eg, one LED per channel), each of which is either off (not working), on (sitting there doing nothing) or blinking (actually doing its job).

It’s a subtle design point, but I feel that taking the LED all the way off before returning back to fully on is a bit harsh on the eyes and the attention. I think it’s environmentally noisy. I propose that UI designers take the brightness down to an intermediate level instead of off. This might be halfway, in terms of power drive to the LED, or it might prove to be something like 90% of full power (or maybe the other way round — 90% reduced power) because of the non-linear way that human perception works. Or maybe a perceptual halfway isn’t as nice looking as taking it down by two thirds, or a third, or 72% apparent brightness, or something.

Technicalogically, this would be slightly unsimpler than simply having a single LED on a single pin of a port of a processor (unless you drive it as PWM). However, if you’ve got two pins on the port to spare for one LED, you could easily do it using the second pin to pull down the drive current via a transistor, or using the second pin to add drive current using resistor summing, or a variety of different ways.

It would look nicer, and that’s the main thing.

Ian Tindale, Jan 19 2011


       Seems reasonable, and I've seen 'multi-tone' LCD screens with varying shades of grey on-screen at the same time, so it's perfectly doable.   

       What would be nice in some applications would be a smooth-transition from on to off, by invoking a kind of ASDR envelope to each LCD-cell's -on- event - that way, you'd be able to construct a single chip with a common interface to control this type of display.   

       [EDIT] later - just realised my mix-up between LED and LCD. Much of the same stuff should apply though, shouldn't it? I think I've seen Christmas Tree lights that show a range of brightnesses, and Apply have that pulsing thing that tells you whether your laptop is on standby or not.
zen_tom, Jan 19 2011

       I'm sure I've seen flashing LED units in the past (some years ago) which have some circuit in them - you just feed in DC and they flash - so, some passive analogue circuit embedded inside. So it should be possible to have something capacitive in there to smooth the sharp edges from your binary drive - i.e.you don't have to use more processor pins or make fancy driver code. And you wouldn't even increase your power consumption hardly.   

       For sure, if the LED is gently pulsating, that would say to me "working", wheras when they are FLASHING ON OFF ON OFF I usually think "oh no - what's the problem ?"
VaquitaTim, Jan 19 2011

       Personally, I hate how everything simply must have an LED indicator nowadays, especially one that indicates that the unit is in 'standby mode.' LEDs may be power-efficient, but their narrow-band light is hard on the eyes, and in the bedroom I go to great lengths, (well, lengths of electrical tape, anyway), to cover them over.
RayfordSteele, Jan 19 2011

       Especially blue leds — read up on “blue light hazard”.
Ian Tindale, Jan 19 2011

       PWM would be OK, if fast enough, and two coloured LEDs would allow the same light intensity but changing from one colour to another.
Ling, Jan 19 2011

       [Rayford] - My bedroom also has bits of black paper taped everywhere to cover the LED's. Electronics stores should sell packs of black sticky paper for $3.95 as an "accessory".   

       Sound beeps should also do this - not "loud - nothing - loud - nothing - loud" but rather "loud - soft - loud - soft - loud". It would be a lot less jarring, and it would be clear when the signal was over, rather than make you wait to hear if there is another beep.
phundug, Jan 19 2011

       Just a note, but the sleep mode on Apple laptops is indicated by something like this (a pulsing LED). In my opinion, however, it gets to bright overall, as it tends to light a room to dark adjusted eyes.
MechE, Jan 19 2011

       No, that’s not this. The heartbeat LEDs on my Macs convey a completely different type of message. The information payload is fundamentally different to the simple “blinkenlight” LED that blinks on and off to indicate activity.   

       As an example, and still within the Apple realm, yesterday I set my Airport Extreeeeem to have the single green LED indicate activity. It certainly does, but it sucks all the attention in the room towards it. So do the lights on the ethernet switch. So do the lights on the BT Homehub. So do portable USB flash drives, so do card readers, etc etc and so on.   

       That’s why I had this idea, and not that one.
Ian Tindale, Jan 19 2011

       bun for "unsimpler"
Voice, Jan 19 2011

       //unless you drive it as PWM//   

       That would be nifty. On and busy could be defined as 20% and 10% respectively for low light conditions. An optosensor could do that job automatically.
bigsleep, Jan 19 2011

       You could even use the LED itself as an optosensor.
MaxwellBuchanan, Jan 19 2011

       I like to blink when the LED is on. At first this can be quite a chore, but after some practice you forget there was ever a blinking light to begin with.
daseva, Jan 19 2011

       You could try blinking when it was off, but then you'd never know if it was off.
MaxwellBuchanan, Jan 19 2011

       Oh for the days of neon tell-tales, Nixie tubes, dekatrons, and those lovely big black Bakelite quadrant meters ....
8th of 7, Jan 19 2011

       //So do the lights on the ethernet switch. So do the lights on the BT Homehub. So do portable USB flash drives, so do card readers, etc etc// So every one of these needs to be retrofitted with, at least, a piece of black tape. The Oedipal solution is much simpler.
mouseposture, Jan 19 2011

       /blinking in time/   

       What if the LED is so bright that when you are trying to sleep, you can see it through your eyelids?
Black tape on your eyes?

       Obviously, here is a great marketing opportunity for infra red LEDs, which can flash as much as they like.
Ling, Jan 19 2011

       //Especially blue leds// blue LEDs are horrible, because they have a wavelngth so much shorter than everything else that they are always (to me at least) out-of-focus. There's a hotel near where I work (where I been for meetings, etc.) which, in a failed attempt to look cool and techy has put rows of blue LEDs along the edges of the steps in its marble staircase - very dangerous.
hippo, Jan 20 2011


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