Led bulbs

Discussion in 'Mech Tech' started by jonno69, Nov 6, 2021.

  1. @Youngdub

    Thanks very much for that, very helpful.

    My indicator relay has stopped working, so I'll get a replacement relay that works with LED bulbs.
    I'll try and get the rest as Christmas presents!
     
  2. Youngdub

    Youngdub Supporter

    No prob - the supplier does the relays I recall. They do bike bulbs too and I did that too - 3 Xmas's rolled into one ;)
     
    paulcalf likes this.
  3. mikedjames

    mikedjames Supporter

    When I fitted the indicators and the tail lights - I also replaced the dash indicator lamp with an LED with a bridge rectifier built in so it works both on indicators/hazards and also the hazards with the ignition off (the voltage goes the other way then .. ) . Failure to change the dash indicator bulb for a LED causes the LED indicators to glow dimly between flashes (but work perfectly otherwise) .

    Filament to the right , LED to the left.
    https://youtube.com/shorts/y5Br7T2JoNQ?feature=share
     
    paulcalf and F_Pantos like this.
  4. did your led dash indicator bulb with rectifier come from classic car leds?
    If so can you point me to it please

    hopefully brighter LED indicators will mean less people ignore me pulling out!
     
  5. mikedjames

    mikedjames Supporter

    Sorry, no, I made it out of a standard dash LED with 4 small diodes soldered in it. I could do better.

    I have just purchased some bridge rectifiers smaller than those diodes - they should squeeze into T5 LEDs with a bit of Dremel action..
     
    Last edited: Nov 9, 2021
  6. Youngdub

    Youngdub Supporter

    Mike are you using the classiccarled relay? Perhaps that eliminates any issue?
     
  7. mikedjames

    mikedjames Supporter

    No, there is a minor issue with all kinds of relays and the way the 1.2 watt dash indicator bulb is wired - the light is wired from ignition switched 12 volts to the output of the relay.
    When the indicator switch is central, no current flows, the bulb is off. When filament indicator bulbs are connected by moving the indicator switch the fact they almost look like a short when cold means when the flasher relay opens its contact, the dash light comes on and the 21W indicator bulbs dont.
    When the LED bulbs are fitted externally the current through the dash indicator bulb is enough to let the external lamps glow dimly . If you dont mind there is no issue.
    Some fixes.. use a LED in the dash.. less current so external indicators dont glow. Or buy CAN Bus LEDs that have shunt resistors. Or fit a resistor to chassis from the output of the flasher relay. Both of these drop the voltage across the external LEDs by drawing current.

    But the one thing the dash LED does is fail to light when hazards are on and the ignition is off as then the ignition switched 12v is at 0v, so the dash LED is reverse biased.
    Either rely on the indicator bulb in the hazard switch or fit a dash LED indicator that lights both ways round...
     
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  8. my rear indicators melted. so swapped back to standard ones. i could smell burning from the cab. also bought from the above.
     
    paulcalf likes this.
  9. LED indicators are sounding less and less like a good idea and more like a potential hassle
     
  10. I'd give up on them. Just a pain. Also: I bought yellow LEDs for my (US-stylee) sidemarkers, and they were a really odd colour. Pah.
     
    Merlin Cat likes this.
  11. mikedjames

    mikedjames Supporter

    Thats installation error - you must have managed to short out the wiring .
    Its not like the LEDS draw more current, just that the connections on the back are in slightly different places, and a bit of pushing and bending and hey presto, the spring connections touch the bulb outer shell connection..
     
  12. mikedjames

    mikedjames Supporter

    I agree, there are a lot of dodgy coloured Chinese LEDs out there, and with LEDs you really need to have ꝊꝚꜸꝴꝗꞓ coloured LEDs in indicator positions.

    Cold White LEDS are actually red plus a big blue peak in the spectrum . Warm white LEDs still are a bit bluish - the effect of these behind even coloured filters is a bit strange.

    The point is that when they are working they are a LOT brighter. And these days you need to be seen..

    Its a bit like on my small yacht, I have an AIS transmitter that tells other boats my speed and heading. I can use it to scare bigger boats out of the way by steering at them at a distance of about 500 metres and triggering a colliision warning... Without it they would ignore me and cut really close..
     
    Last edited: Nov 11, 2021
  13. HMM not sure - its plug and play - the burnt face was the led soldered to the backing face just moved house so threw it out or i'd show a pic
     
  14. mikedjames

    mikedjames Supporter

    Were those eBay or Classiccarleds ones ? The eBay ones can be quite close to shorting out from the start...its up to the worker who doesnt care, not paid enough, to solder or spot weld it ..
     
  15. mikedjames

    mikedjames Supporter

    Heres a rework of a dash LED to make it bidirectional..
    I used a surface mount LED and a little bridge rectifier (about 10p each..if you buy 50. ) to replace the 0.2" LED.
    20211118_080130.jpg 20211118_122923.jpg 20211118_123352.jpg 20211118_123648.jpg
     
    Norris likes this.
  16. Clever!
     
  17. Of course if you fit Lead's without a voltage regulator you will shorten their life. Lead's run on 12v where the out output from an alternator while running can be almost 14v. Does not sound like much but LEDs are sensitive. I have had some DRLs burn out in under 6 months. Fitted a regulator and all good.

    Sent from my AC2003 using Tapatalk
     
  18. They’ll run fine from a 12-14V supply ;). They’ve got limiting resistors built in anyway (otherwise they’d go pop running off 12V).
     
    SkutterBob likes this.
  19. mikedjames

    mikedjames Supporter

    Actually there are two ways to run LEDs. - and @SkutterBob is right...
    The cheap eBay way is three LED chips in series, with a limiting resistor.
    The forward voltage of each LED chip is about 3 volts so the stack of LEDs drops 9v, the resistor drops 12v - 9V or 3 volts at the specified current.
    If you wind up the DC input to 14-15 volts, the resistor now drops 5-6 volts. As the current doubles with the voltage doubling , the power goes up 4x, and the LEDS get 2x the current and start to cook as well.

    Basically the DRLs that @SkutterBob purchased are these type.

    On the eBay description they will say 12 volt operation. The only advantage of these is that you dont get radio noise generated by the resistors.

    I have a replacement festoon LED bulb in the dome light on my bus which gets so hot the resistor desolders itself if the battery voltage is 13.8 to 14.2 volts on charge on hookup power and you leave the light on..

    If you buy LED bulbs from a more expensive vendor or Classic Car LEDs they cost more - and that is a clue.

    In these there will also be a switch mode boost converter, and there will be longer strings of LEDs, maybe 10 or more. These 10 LEDs need 30 volts to light up, so a DC-DC boost power supply chip is fitted.
    This chip limits the current without using heat generation in a resistor to control the current - it averages the current by storing a varying amount of energy in a coil.
    These units are often specified to work from 6 to 24 volts and dont care about polarity - certainly thats the spec of e.g. the Classic Car LEDS H4 headlamp bulbs.

    Generally look to pay more and you will get better quality.

    The downside is that unless you buy specifically CE marked parts, (extra cost again) they may generate radio interference from the power supply chip.

    Its why e.g. the ClassicCarLeds headlamp supplies have a powersupply box that is half the size of a credit card giving space for radio interference filtering, while some of my 6-24 volt eBay specials have a power supply circuit about 7mm square stacked in the base of the LED assembly, with no provision for radio interference filters.
    I have become aware of some H4 headlamp units with "Angel Eyes" that knock out DAB for instance.

    Just remember - a Chinese vendor can get
    • A subsidy for selling overseas
    • Landfill tax rebate for getting landfill out of China.
     
    Last edited: Dec 6, 2021
    Kruger, mcswiggs and SkutterBob like this.
  20. Do these actually fit in the bowl and more importantly,in the back of the headlamp itself? I have tried some cheaper LEDs off eBay,but I couldn’t fit the metal securing ring on top to hold them in place.


    Sent from my iPhone using Tapatalk
     

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