Fixing an SJ-269SE LED Daytime light

 

This is how it should look like (thepontiactransampage.com)

Normally, the Firebird's front turn signals double as "parking" / daytime running lights, but on this side of the Atlantic, these lights must be white. This rule is enforced quite randomly though; this time the car's previous owner got the short straw, and had to install these ill-suited aftermarket DRLs.

Of course, one of the aftermarket lamps had to fail. As Mr. Previous Owner wasn't one to waste his time on storing receipts or other documentation, warranty replacement wasn't an option either. The device itself is insanely simple (apparently a power regulator, some resistors and 5 LEDs), but (on account of ECE standards compliance?), they tend to cost around 50-100 eur.

Hence, the need to fix the MyCARR SJ-269SE, in as ECE-R7 compliant a way as possible, and to document it here. The device's conformance inspection report says it should emit 30 cd of light with about 20-30 degree horiz./vert/. angle, i.e. 6 cd per LED.

I tested three different LEDs:

• LL-504WC2E-W2-1ED (10cd, 25 deg)
• 5W4UCCC WARM (16-21cd, 20deg)
• LiteOn LTL-33BCWK5A (6 cd, 20 deg, actually 4.6 mm)  -- The winner
• specs
• http://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTL33BCWK5AT.PDF

Of these three, the latter one is a nearly identical match for intensity, emission angle and color tone. The flat ones in the pic are the unit's original LEDs, the 33BCWK5A is the tall one in the middle.

I later found what looks very much like the original LED, http://uk.rs-online.com/web/p/visible-led/7134876/

Three of the original LEDs were still working, and as they fit the reflector better than the common bulb type, I kept those in the center.

They're connected in series with current limiting resitors, in two parallel groups, like this


(+)-----------+--------------\
14V           |              |
            R1 =           R2 =
            52 ohm         270 ohm
              |              |

             _|_            _|_              

             \ /            \ /

             ---            ---

              |              |

             _|_            _|_              

             \ /            \ /

             ---            ---

              |              |

             _|_             |

             \ /             |

             ---             |

              |              |

(-)-----------+--------------/

            orig.           new

            LEDs            LEDs

      14V - (3 * 3,8V)

R1 = ------------------  = 52 ohm

           0,05 A

      14V - (2 * 3,7V)

R2 = ------------------  = 246,66.. ohm

           0,03 A

The LEDs' voltages and max. currents (3,8 V / 50 mA and 3,7 V / 30 mA) come from the datasheets and seller's specs.

After experimenting, I ended up with 270 ohm for R2 to get similar brightness from both LED types.

There's more on LED circuits at http://www.kpsec.freeuk.com/components/led.htm

I've yet to test how it looks like next to the original light.