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The LED lighting thread

PostPost by: Spyder fan » Thu May 25, 2017 4:00 pm

Craven wrote:IIRC there may some issues with regards twin filament LED’s and the UK MOT, these clever LED lamp makers produce a single array of 21w and tap off to give the 5w. OK but that means in practice Max output being 21w, applying the brake at night only increases the output by 16w. It will be interesting to see if Alan’s appraisal includes this observation.
FWIW
Ron.


Ron,
I think that's a very good point and I will be sure to do the test in a dark garage with tail lights on before applying the brakes. I will probably get Mrs T to dab the brakes while I do photo's leaving one side standard for comparison. The cost of the bulbs is only £9.95 inc postage for the pair, if they are an improvement then that's great, if not then there's not a lot of money wasted and I always have the 14 day rule to return them if I think they are totally not fit for purpose.
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PostPost by: Chancer » Thu May 25, 2017 4:45 pm

Its time the lighting régulations came into the 21st century and rated bulbs by luminous intensity/candlepower instead of watts, 21 watts of LED light is a whole lot brighter than incandescent, great for safety regarding brake lights but there is a risk of dazzling following vehicles for rear lights, existing rear fog lights when misused are a real hazard.

130 watts of led light facing forward would be blinding and the light output per watt just keeps increasing.

As an aside regarding home LED spotlights which may be relevant to the made to the lowest cost car bulbs, I have 7 watt (7 * 1 watt led) spotlights across all my rental properties, a couple of hundred fittings, to date the daylight ones have been reliable except a couple of transformer failures but after a few years am probably approaching 100% failure of the warm white ones dependant on how long they have been running, at first I could not see how to get them apart and dint think they could be repairable so was throwing them out as I had plenty of spares.

Then when they kept failing I found that I could get them apart and indeed repair them, they are in fact just 7 LEDs in a series circuit with no other components, one fails (usually a heat sink problem) and the remaining 6 go out, this could have serious implications for the multi-led car bulbs if they also are a series circuit, the more leds per bulb the greater the odds of failure.

In my case one failed spotlight yields enough leds to repair 6 others, testing is dead easy, just shunt out each led in turn, when you get to the failed one the others all light up.
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PostPost by: mbell » Thu May 25, 2017 6:24 pm

Chancer wrote:Then when they kept failing I found that I could get them apart and indeed repair them, they are in fact just 7 LEDs in a series circuit with no other components, one fails (usually a heat sink problem) and the remaining 6 go out, this could have serious implications for the multi-led car bulbs if they also are a series circuit, the more leds per bulb the greater the odds of failure.


That is a good point. With most LEDs being 2-3v on the 12v car it is highly unlikely that a single failure would take the full light out. As with the LED count there must be a number of parallel circuits with multiple LED in serial on the bulb, rather than a single serial circuit.

However failure of one of two LED might lower the brightness output to a concerning level without being obvious from a quick light check.
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PostPost by: Quart Meg Miles » Thu May 25, 2017 10:16 pm

mbell wrote:
Chancer wrote:However failure of one of two LED might lower the brightness output to a concerning level without being obvious from a quick light check.

Few people notice the lower output of their lamps when they have the classic earth fault in their dual filament lamps, until they notice the whole unit goes out if tail and stop lamps are both active. How many people know their lights are working at all?

Refering to an earlier part of this thread, the difference between 21+5W vs 21W is small, less than 1 dB in a change of 7 dB between tail and stop power, and can be ignored. The eye is logarithmic like the ear otherwise we wouldn't cope with the brightness range we experience.
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PostPost by: Craven » Thu May 25, 2017 11:48 pm

meg
I find your comments interesting, what is your 0 db reference. Are you commenting on the eye performance in daylight or the practical situation of night vision?
Alan, a further point in your appraisal, apparently if you are still using normal turn indicators 21w bulbs the stop/brake light will vary in intensity in sync with flasher!!
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PostPost by: Spyder fan » Fri May 26, 2017 6:42 am

All very interesting.

I had been warned previously that the flasher unit or circuit would need to be altered due to much lower current drain of the LED bulbs, so I was ignoring these for the time being. At the moment I'm more interested in visibility on the road at night and having brighter stop lights day and night. Slightly brighter side lights would be good as well, so that I can use them as daytime running lights.

I have added a "check the indicators don't make the stop lights vary in intensity" to the appraisal list.
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PostPost by: Quart Meg Miles » Sat May 27, 2017 3:39 pm

Craven wrote:meg
I find your comments interesting, what is your 0 db reference. Are you commenting on the eye performance in daylight or the practical situation of night vision?
Alan, a further point in your appraisal, apparently if you are still using normal turn indicators 21w bulbs the stop/brake light will vary in intensity in sync with flasher!!
Ron.

Ron,

I was meaning the performance at night time when applying brakes with sidelamps already on, the 0 dB reference point. So with filaments the Stop lamp is a 7 dB step but with the LEDs, as described earlier, 6 dB. In the absence of direct comparison it wouldn't be noticed and present car lamps vary considerably more than that between makes.

While stacked LEDs will be pretty sensitive to voltage changes, assuming they don't use proper regulation, any significant brightness change due to other proper bulbs flashing still indicates poor earthing or shared power wiring.

I'm biased against LED signal lamps on cars, their unnaturally immediate appearance/disappearance seems too confuse my eyes and make the signals less visible, especially in lamp clusters; does anyone else experience this?
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PostPost by: Craven » Sat May 27, 2017 10:11 pm

Meg,
Alan’s practical feedback will be interesting, the phenomenon of sympathetic pulsing of stop/brake light with turn indicator is fairly well known. Several explanations have been put forward on other forums, most common being the LED’s fast response time causing their output to follow any pulses in the supply not normally seen by the slower filament bulb. Poor earth return was my first thoughts when trying to fix this but not so, even doubling up on common supply lines did not completely stop the effect.
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PostPost by: Chancer » Sat May 27, 2017 10:28 pm

I'm biased against LED signal lamps on cars, their unnaturally immediate appearance/disappearance seems too confuse my eyes and make the signals less visible, especially in lamp clusters; does anyone else experience this?

Something similar, here in France traffic lights have little repeater lights lower down the pole at driver level so you dont have to crane your neck and look up, they are all LED's of course now, on one junction only when I pull up, if I am looking forward and the red light is in my peripheral and not the macular vision it flashes, if I turn my head or swivel my eye (singular as my left one is effectively blind) its no longer flashing, this only occurs when I am driving my RHD ex UK car, if I drive a LHD car the angles are different but it should be even further to my peripheral vision, I have never worked it out and no-one else can see the flashing.

I can also see the blue light from a UV lamp be it a bank note tester and supposedly invisible IR beacons on aircraft or CCTV IR floodlights but I know the reason for that, the flickering red LED remains a mystery yet to be solved.
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PostPost by: elanfan1 » Sat May 27, 2017 11:17 pm

might be a question to put to your Opthalmic consultant at your next appointment. I've had a few thousand laser shots in my eyes and it's weird what that does in the very short term but in the longer term I still see flares from streetlights at night. I know they aren't there but still I see them - Weird!

Some great input here please keep it up. Be good if someone could populate the bob holder sizes.

Once we get some proven good quality led units perhaps we can approach a manufacturer to make up a conversion kit which would make life a lot easier.
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