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    Rear light clusters

    Hi All,

    Has anyone replaced their rear light clusters with LED ones? Having water ingress issues, so need to sort my rear lights out anyway, and was wondering if I could change to a brighter set at the same time.

    Thanks
    Mike

    #2
    Originally posted by sevencranes View Post
    Hi All,

    Has anyone replaced their rear light clusters with LED ones? Having water ingress issues, so need to sort my rear lights out anyway, and was wondering if I could change to a brighter set at the same time.

    Thanks
    Mike
    LEDs are great at conserving power. The main advantage, but not of particular relevence on lamps mostly only used when the engine is running and charging the battery, is the very significant saving in battery power needed.
    The other advantage of virtually unsure value, is claimed to be longer life. But bearing in mind that replacement LEDs are less likely to be handy to obtain, there may be less advantage in life span.
    Lastly. Brightness is not likely to be much of a factor because replacement LED units are likely to be intended to simulate brightness and visibility of the originals anyway.

    Finally the water corrosion in light units is likely to affect LED (connections) just as much as bulbs if water gets into the unit.

    I am wholly in support of LEDs for the domestic side of a caravan or motorhome, but consider them less desireable or necessary for the motoring aspect.

    I see nothing wrong with LED road lights. I even have an LED rear lamp on my classic bike - but that is to allow the use of a better headlamp with the limited charging facility of its time.

    I am not trying to dissuade anyone. Just to present "food for thought".

    Jim

    P.S. I think I have noticed a slight decrease in the light output of the LEds in my caravan lately, though they are now several years old. Or is it my imagination?
    Last edited by Twolitre; 08-12-2013, 09:07. Reason: P.S.Added
    Keeping people waiting is stealing a part of their lives.

    Comment


      #3
      Pulsing effect

      I'd support Jim's position on this ... and worry first and foremost about solving the water ingress problem which is always going to be coming back to bite you whatever light source you use.

      Apropos of nothing in particular, but I mention it because we are talking about LEDs, I was watching a slow-motion video of a car with LED tail lights the other day and noticed that they were seen to be pulsing (in the same way that Fluorescent tubes do in time with the 50 cycle AC supply). We see the light produced as steady because of 'persistence of vision'. HOW COME? Since cars run on 12v.dc is there a gadget in there that effectively switches the LEDs on-off-on-off very fast for some good reason.... like energy saving?

      Comment


        #4
        You can get more lumens out of a LED junction if you put a short pulse of current through it. So you get a brighter and more efficient light by pulsing the led.
        I addition to this it is best to properly control the current through the LED and this can also be controlled by switching the regulator.

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          #5
          All the vehicles with LED lights I've seen use clusters of diodes. To me that means that if it fails, it might do so partially, rather than dying altogether, like a regular bulb. Except if the failure is in the wiring of course.

          Comment


            #6
            Originally posted by JimD View Post
            All the vehicles with LED lights I've seen use clusters of diodes. To me that means that if it fails, it might do so partially, rather than dying altogether, like a regular bulb. Except if the failure is in the wiring of course.
            It is generally easier and cheaper to achieve the required lumens using multiple cheaper LED junctions with a larger area of distributed heat dispersion than a single much higher output LED with a much smaller area to dissipate heat.

            If these Auto LED bulbs are designed to replace the filament bulbs then they must have multiple junctions to provide the 360 degree light output that you normally get from a filament. This is particularly the case if the light unit has reflectors in it.

            In reading lights they often have multiple junctions to give a better angle of spread.

            The new purpose designed light units in the latest cars are often multiple LEDs to provide more artistic lines and curves purely as a feature.

            Comment


              #7
              LEDs are normally of a lower voltage than vehicle electrics.
              Accordingly they are either wired up in series (end to end) so the sum of voltages required equals the supply voltage. In which case if ONE fails all in that "string" fail - like fairy lights which are generally wired up the same way with small voltage bulbs.
              OR, they are wired individually in series with a resistor. In which case only one LED failure at a time wil leave the others lit.

              As for "pulsing". As I mentioned earlier, I have rear LEDs on my motorbike which is only six volts. In spite of ensuring all electrical connections are clean and sound I CANNOT stop the light pulsing in time with the retro fitted turn indicators. So I found the mention of voltage pulsing interesting.

              Jim.

              P.S. I know I said I was shutting down earlier to go to bed! Did so! Couldn't sleep! So got up and just clearing up a bit more before I commit another one and a half hours travelling to Manchester Airport for a 7a.m. check in.
              Keeping people waiting is stealing a part of their lives.

              Comment


                #8
                Originally posted by Twolitre View Post
                LEDs are normally of a lower voltage than vehicle electrics.
                Accordingly they are either wired up in series (end to end) so the sum of voltages required equals the supply voltage. In which case if ONE fails all in that "string" fail - like fairy lights which are generally wired up the same way with small voltage bulbs.
                OR, they are wired individually in series with a resistor. In which case only one LED failure at a time wil leave the others lit.
                LEDs are Diodes. They are current conducting devices and in no way resemble resistive incandescent lamps. They are capable of conducting quite large currents to the extent that they will self destruct if the current is not controlled. LEDs have a forward voltage threshold which has to be exceeded before the junction starts to conduct. This can be between 1.5V to 5V dependant on the size and type of the junction. You can stack LEDs (connect in series) as many as you like provided the sum of the forward voltage thresholds does not exceed the supply voltage, otherwise there will not be enough potential for the stack to conduct. However you must still control the current either by a series resistor or a current controller. By stacking multiple LEDs you can reduce component count and power dissipation.

                Originally posted by Twolitre View Post
                As for "pulsing". As I mentioned earlier, I have rear LEDs on my motorbike which is only six volts. In spite of ensuring all electrical connections are clean and sound I CANNOT stop the light pulsing in time with the retro fitted turn indicators. So I found the mention of voltage pulsing interesting.
                This is not high frequency pulsing as discussed earlier in this thread but a change in brightness of the LEDs in synchronism with the other incandescent flashers.
                The incandescent bulbs and even the flasher timer element take quite a high initial current surge until the element heats up. Thus on a motorcycle with a 6V battery there will be quite a significant quarter of a second power drop as the bulbs heat up particularly if the wiring is not thick. The LEDs on the motor bike probably have a series resistor and not a current controller and it is possible the voltage could drop below the forward threshold of the LED(s) or in any case the resistor would see the total of the voltage drop as the voltage drop across the LEDs would be constant. Thus the voltage drop across the resistor could be as much as 90% of the normal drop resulting in a considerable drop in current and resultant output from the LED(s). One way to stop this is to put a filter in the supply to the LED(s) consisting of a series forward diode and a say a 200 microfarad electrolytic capacitor across the power at the point it connects to the LED(s)

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