Blinking Light pattern for maximum attention distance at night

[Wilson__]

What Brinking Light on-off pattern has maximum recognization distance? at night after sunset with some man-made light in background, natural moon light and no fog/mist? 

Person is attentively seeking for the guide light. 

Maximum distance means the light is dim.

Examples are stroke red light on aeroplane top and bottom, white light on runway lead-in section (running ball of light) and red light on tall buildings.

Many thanks

 

[soldar]

Flashing/strobing. Max power with minimum duty cycle. Directional if possible. Repetition rate ... dunno... depends on particular circumstances, not too frequent, not too long. Needs more frequent to first catch, less to keep locked. Start with a nice round numbre: 1 flash per second.

[johansen]

3 pulses in 1 second, followed by one pulse per second, repeat. universal sos is pretty recognizable to the human brain.

[Benta]

"Mr. President, when was your last election?"
"This morning, just before bleakfast."
 

[themadhippy]

seem to recall the eye is most sensitive around the 6hz area,and  the standard "im lost can anyone  see me " is 6 flashes a minute with a minute gap.so id be tempted to strobe the light at 6hz with  5 seconds  strobe 5 seconds off repeated 6 times and then a minute off

[jpanhalt]

For me, an easy pattern to recognize is two rapid pulses followed by a longer pause.  As variation is two blinks followed by one blink A consistent blink is harder to distinguish from stars.  Although an SOS is probably easy to recognize, I don't think that's a good idea unless there is an emergency.

[BrianHG]

Make sure you use a massive Xenon strobe tube.  Careful about getting too close or looking into one, they can easily blind you.  Also, make sure you have a glass cover or film gel which blocks most of the UV coming out of it.

Also keep paper or wood away from the front of it.  The bright one are so strong that you can get instant flash-fire ignition.

Expect the strong ones to be seen for a few 10s of miles if you have a basic reflector and line of sight.


Example mid power one: Mid-High power Xenon  (Strong enough to instantly flash a sheet of paper into flames and burn your skin)

These modern still in production ones are probably in the power range you need:
https://www.xenonflashtubes.com/flash-lamps-by-shape_10

This 6$ one with a directional reflector should do:
https://www.xenonflashtubes.com/spiral-helical-flash-lamps/40w-spiral-strobe-flash-tube-lamp_79.html

Also take a look at the stage lighting Xenon drivers and bulbs.  They are designed to run up to 12hz with an external trigger and they can maintain ~1kw average output.

Note that you wont find the huge high power Xenons which used to be used for spy plane photography.  Those were designed to light up a small city from a few miles above during the night before the days of digital spy satellite technology.

[themadhippy]

Example mid power one: Mid power Xenon  (Strong enough to instantly flash a sheet of paper into flames and burn your skin)

pah a mere 8kw,you really need 10x that to get noticed.https://hungaroflash.com/termekek/t-light-pro-85000w/

[BrianHG]

Example mid power one: Mid power Xenon  (Strong enough to instantly flash a sheet of paper into flames and burn your skin)

pah a mere 8kw,you really need 10x that to get noticed.https://hungaroflash.com/termekek/t-light-pro-85000w/

Now we are talking...

[BrianHG]

Use this guy if you want an entire city to unquestionably see you with a single flash:
https://invention.si.edu/seeing-dark-aerial-reconnaissance-wwii

[LaserSteve]

Actually IALA, the International  Association of Lighthouse Associations, has nice range equations published for this. As did thevUS Coast Guard at one time. Pulse Pulse Pause, is highly effective as is Morse Code Letters S and H.  If you can create the Illusion of movement, aka Airbus wingtip strobes, vs Boeing, you get far better detection vs background.

Steve

[BrianHG]

@Wilson, sorry for going to town on your thread.  The point I was making was make the light sharp and bright.  For huge distances, think like the strobe you see in the night sky from aircraft.  Those are only 40-200watt bulbs.  For something on the ground, battery powered Xenon strobe emergency beacon lights already exist which flash once a second and can be seen over a mile away if anyone is looking in that direction.  These strobes are using the cheap tiny 1-2$ xenon flashes used in small dance disco lights or older cameras from 15 years ago before super bright LED and digital cameras could operate under low LED light conditions without severe grain.

Look at the products and videos for ideas here:
https://www.made-in-china.com/products-search/hot-china-products/Xenon_Beacon_Warning_Light.html
(You know the real Xenon ones are the ones which the video camera can't properly capture, the other sad dim ones which you can see are the LED types...)

[Wilson__]

Did LED flash bright enough now and replace xeon tube for camera build-in flasher?  Guide number of says 10, for photo of a few people group at a few meter away?

[jpanhalt]

Actually IALA, the International  Association of Lighthouse Associations, has nice range equations published for this. As did thevUS Coast Guard at one time. Pulse Pulse Pause, is highly effective as is Morse Code Letters S and H.  If you can create the Illusion of movement, aka Airbus wingtip strobes, vs Boeing, you get far better detection vs background.

Steve

(dit dit, ..) is "i' in Morse code.  It is very easily recognized and is the initial letter of ILS beacons followed by a location identifier.  I wonder whether many pilots even bother listening to it nowadays.  For me, it was always a "welcome home."  "Hi" is "dit dit dit dit" pause "dit dit."  You might hear cars with license plate call signs do that on the highway with their horns -- at least in the US.     I've not heard that in awhile.

[BrianHG]

Did LED flash bright enough now and replace xeon tube for camera build-in flasher?  Guide number of says 10, for photo of a few people group at a few meter away?

No, led does not flash bright enough to replace a camera xenon flash.  What has happened is that your phone's camera can now operate with 1/100th the light output without delivering a picture full of grain/noise.

You wont find a film camera using 25ASA or 100ASA film being exposed with a led flash.
The xenon flashes usually around 100x faster, and simultaneously delivering over 1000x (guesstimate) the flux.  The xenon bulb's output are even measured in 'Joules' of energy.  The cheapest camera xenon flashes strike at 300v-600v, with something like 50 to 100 amps.  That's a ~30,000 watt pulse.  Driving an led at 300v by 50 amps wont shine at all, it will just blow up.

I guess in today's world, not many have seen a true xenon flash bulb in person.

[CaptDon]

Brinking lights only certified for use in Japan, elsewhere specify the blinking light equivalent.

[Doctorandus_P]

I am not so impressed by those Xenon things.

When I follow the link to youtube I see an 240000 lm output for 8000W lamp. That is only 30lm/Watt.

White LED lighting can get 200lm per Watt. Green led's can have a higher light output per Watt.

Efficiency of LED's goes down with higher power input. If you take two 10W LEDs, and drive them both at 5W, they will have more light output then a single 10W LED driven at 10Watt.

This also implies you do not want to PWM the LED's, With a steady constant current, you avoid the higher current peaks where efficiency goes down.

[Someone]

I am not so impressed by those Xenon things.

When I follow the link to youtube I see an 240000 lm output for 8000W lamp. That is only 30lm/Watt.

White LED lighting can get 200lm per Watt. Green led's can have a higher light output per Watt.

Efficiency of LED's goes down with higher power input. If you take two 10W LEDs, and drive them both at 5W, they will have more light output then a single 10W LED driven at 10Watt.

This also implies you do not want to PWM the LED's, With a steady constant current, you avoid the higher current peaks where efficiency goes down.

While luminous efficacy of an arc lamp may be "poor" compared to an LED, it can compress the power into incredibly short pulses which an LED cannot. If you need a short pulse then it can be a good (or the only) choice.

[BrianHG]

When I follow the link to youtube I see an 240000 lm output for 8000W lamp. That is only 30lm/Watt.

White LED lighting can get 200lm per Watt. Green led's can have a higher light output per Watt.

Ok, how many expensive 5w green led can you cram into a single point to attain a 240,000 lm pulse?
120 5watt leds?  We aren't talking about the 1watt leds.
Concentrated into a tiny package.
Luckily with such a low duty cycle, you might not need any heat sink.

Optics and packages for a huge 100watt spot led (usually made with smaller segments) can be purchased, circuit designed and manufactured.  It will take a lot of work as you want a 100watt current regulated pulse, but don't need the continuous constant power output if you want this device to run off of 2-4 batteries.

If you want continuous output, think along the lines of those DIY insane bright LED flashlights.  Your looking for a pulsed version of those where the pulse length will be around 0.1 or 0.05 seconds for human eye visual brightness instead of the less than 0.0001 second pulse of a xenon camera pulse.

[NiHaoMike]

Although an SOS is probably easy to recognize, I don't think that's a good idea unless there is an emergency.

There used to be a popular ringtone that's similar to SOS but with a crucial difference - only two long beeps instead of 3. So it's similar enough to catch attention but different enough to not be mistaken for an actual emergency call.

[LaserSteve]

Nothing Xenon in this thread other then Edgerton's lamp is even close to what I've used for laser pump lamps.  Hungaroflash's technique is to place the tube across the AC power line, and use the wiring inductance to limit current.  Others do that too, picking the trigger point towards the end of the AC half cycle.

Great technique, and I've used it, but the pulse is long, and the lamp fill  pressure is very low,  so the peak energy is low. Thus luminous   efficiency is low.

Steve

[Wilson__]

Is it better human-attention with two colour flash or single colour LED that has the highest mcd output? 

Different colour LED has different light output at same current.  So far from datasheet search, green has higher output mcd, typ 2.8 max 3.05V, fit 3.7V Li ion cell.

[MarkT]

The problem needs better definition - brighter is always more visible - so what is the constraint for the blinking pattern - is the peak brightness (power) fixed or the average brightness (power) fixed - the latter is natural for battery powered equipment where battery life is the limitation - in that circumstance short very bright pulses are perhaps the best.

If you are limited to a particular peak brightness I would suggest a high duty cycle for maximum use of that peak level, with short off-periods to attract attention.

I suspect there is some literature on this problem from way back about optimum lighthouse flash patterns, might be worth a search.

[coppercone2]

i heard they had special bombs filled with xenon or helium and they would use high explosives to compress it to get a bright flash https://en.wikipedia.org/wiki/Argon_flash

[Wilson__]

It is for night time use.  Design variables are:

Steady vs flashing.  Flash distingusih from moonlight or background man-made light.  Save battery too

Flash pattern.  How brain react best to certain pattern?

Colour.  Which color is best recognize by huamn eye at low intensity level (far away long working range)?