Blinking Light pattern for maximum attention distance at night - Page 1
Forum section: electronics / projects

author: Wilson__
author_rank: Frequent Contributor
timestamp: April 30, 2024, 04:47:57 am
content: WhatBrinking Light on-off patternhasmaximum 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

author: soldar
author_rank: Super Contributor
timestamp: April 30, 2024, 06:07:28 pm
content: 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.

author: johansen
author_rank: Super Contributor
timestamp: April 30, 2024, 06:12:14 pm
content: 3 pulses in 1 second, followed by one pulse per second, repeat. universal sos is pretty recognizable to the human brain.

author: Benta
author_rank: Super Contributor
timestamp: April 30, 2024, 09:16:16 pm
content: Mr. President, when was your last election?"This morning, just before bleakfast.

author: themadhippy
author_rank: Super Contributor
timestamp: April 30, 2024, 10:10:51 pm
content: 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

author: jpanhalt
author_rank: Super Contributor
timestamp: May 01, 2024, 01:13:38 am
content: 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.

author: BrianHG
author_rank: Super Contributor
timestamp: May 01, 2024, 01:39:16 am
content: 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_10This 6$ one with a directional reflector should do:https://www.xenonflashtubes.com/spiral-helical-flash-lamps/40w-spiral-strobe-flash-tube-lamp_79.htmlAlso 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.

author: themadhippy
author_rank: Super Contributor
timestamp: May 01, 2024, 02:00:11 am
content: Quotepah a mere 8kw,you really need 10x that to get noticed.https://hungaroflash.com/termekek/t-light-pro-85000w/

author: BrianHG
author_rank: Super Contributor
timestamp: May 01, 2024, 02:01:27 am
content: Quote from: themadhippy on May 01, 2024, 02:00:11 amNow we are talking...

author: BrianHG
author_rank: Super Contributor
timestamp: May 01, 2024, 02:14:02 am
content: 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

author: LaserSteve
author_rank: Super Contributor
timestamp: May 01, 2024, 02:44:04 am
content: 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

author: BrianHG
author_rank: Super Contributor
timestamp: May 01, 2024, 02:49:17 am
content: @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...)

author: Wilson__
author_rank: Frequent Contributor
timestamp: May 01, 2024, 05:06:01 am
content: 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?

author: jpanhalt
author_rank: Super Contributor
timestamp: May 01, 2024, 10:04:19 am
content: Quote from: LaserSteve on May 01, 2024, 02:44:04 am(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.

author: BrianHG
author_rank: Super Contributor
timestamp: May 01, 2024, 04:49:22 pm
content: Quote from: Wilson__ on May 01, 2024, 05:06:01 amNo, 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.

author: CaptDon
author_rank: Super Contributor
timestamp: May 02, 2024, 01:22:18 am
content: Brinking lights only certified for use in Japan, elsewhere specify the blinking light equivalent.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 02, 2024, 02:04:38 pm
content: 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.

author: Someone
author_rank: Super Contributor
timestamp: May 02, 2024, 11:37:04 pm
content: Quote from: Doctorandus_P on May 02, 2024, 02:04:38 pmWhile 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.

author: BrianHG
author_rank: Super Contributor
timestamp: May 03, 2024, 12:19:06 am
content: Quote from: Doctorandus_P on May 02, 2024, 02:04:38 pmOk, 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.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 03, 2024, 01:47:36 pm
content: Quote from: jpanhalt on May 01, 2024, 01:13:38 amThere 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.

author: LaserSteve
author_rank: Super Contributor
timestamp: May 04, 2024, 03:43:12 am
content: 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

author: Wilson__
author_rank: Frequent Contributor
timestamp: May 04, 2024, 07:28:45 am
content: 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.

author: MarkT
author_rank: Frequent Contributor
timestamp: May 04, 2024, 08:19:38 am
content: 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.

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2024, 08:29:28 am
content: i heard they had special bombs filled with xenon or helium and they would use high explosives to compress it to get a bright flashhttps://en.wikipedia.org/wiki/Argon_flash

author: Wilson__
author_rank: Frequent Contributor
timestamp: May 04, 2024, 08:42:01 pm
content: It is for night time use. Design variables are:Steady vs flashing. Flash distingusih from moonlight or background man-made light. Save battery tooFlash 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)?

author: jpanhalt
author_rank: Super Contributor
timestamp: May 04, 2024, 08:48:30 pm
content: Quote from: Wilson__ on May 04, 2024, 08:42:01 pmHaven't the first three already been answered. Flashing with a regular pattern, but probably not simply on/off.As for color at night? Have you heard about our rods and cones? Look up night vision.

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2024, 09:37:33 pm
content: i heard conflicting information on colors. best to try it yourself

author: 5U4GB
author_rank: Super Contributor
timestamp: May 05, 2024, 09:39:56 am
content: Quote from: BrianHG on May 01, 2024, 01:39:16 amWouldn't flying a US military aircraft over a Soviet city and then lighting it up with a bright flash have risked, you know, misinterpretation by the other side?

author: 5U4GB
author_rank: Super Contributor
timestamp: May 05, 2024, 09:45:03 am
content: Quote from: BrianHG on May 01, 2024, 04:49:22 pmOutside of specifically phone-camera use they are bright enough, to the extent that they're used in lighthouses and are visible for tens of km (you can run an LED lighthouse off solar-charged batteries, which is great for remote and automated lighthouses).

author: LaserSteve
author_rank: Super Contributor
timestamp: May 07, 2024, 05:16:15 pm
content: Day peak eye sensitivity is around 570 nm yellow. Night peak is around nm green.Flashing is a must against urban background lighting. Daylight Warning strobes for radiotowers are 30-60 short [ xenon strobe ] flashes per minute, switching to short bursts of flashes at night at reduced power and reduced rate, often with a change of color to red. The night adapted brain is confused by a single flash but very much adapted to locating bursts of short flashes.Aeronautical warning lights have always had a secondary use for navigation back to the 1930s, so they have far higher intensities then they actually need.Alternating green and yellow or green and white single flashes makes for a strong means to locate a position, which is why that particular sequence is legally reserved for locating airports in the US.200 to 1000 microsecond flashes l Xenon) [actually out to 100s of milliseconds] win, period. Running them in burst-pause-burst makes them distinctiveIALAs quick flashing and occulting patterns come in second.Alternating the location of flashes aka wig-wag aircraft lighting comes in third.Alternating color in short bursts comes in fourth.The US FAA has this well spelled out for Anticollision, Tower, and Airport Beacon lighting in various regulations.Recently in the US, alternating yellow green, of a pattern distinctive from the Aviation Beacon pattern has been adapted for construction vehicles on highways. in my State, Ohio, it was so effective on winter snowplows that a petition circulated to the governor's office to tame it by reducing intensity. It uses alternating colors and motion, and it is Highly effective.https://youtu.be/X5G2Ya0ZaJ0?si=eN9nHL5FAubGEswbhttps://youtu.be/ZAGZVblbS3U?si=S0ro6vgBL_ynvYyIOhio State trucks now use alternating yellow and white in the upper left and lower right and alternating green yellow in two other locations on the rear. Colors "flip" about twice per second. Using four spaced beacons with a quadrature phased [90 degree] color wig-wag sequence is amazingly effective.State Law had to be amended to have green lighting on a vehicle, and requires it to be distinctive from traffic lights at intersections.Do the pilots a favor and make your sequence different from Morse Code H, white yellow green, white green, white yellow, white white green, beacons.Steve