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Archive for January 9th, 2018

Eyebrow Lights

A high energy collision / accident / mishap in front of Adams Fairacre Farms (a.k.a., the grocery store) demolished 20 feet of their dry laid stone wall along Rt 44, flattened several bushes, gouged trenches in the grass, and scattered plastic debris into the parking lot. The remains of a headlight eyebrow running light emerged from a snow pile:

Eyebrow light - front

Eyebrow light – front

From the back:

Eyebrow light - back

Eyebrow light – back

Contrary to what I expected, it has one white LED at each end of the chromed reflecting channel, topped with a shaped plastic lens collecting the light:

Eyebrow light - Lens mount

Eyebrow light – Lens mount

The LED PCBs are in series, which produced a backwards wire color code on one end:

Eyebrow light - LED PCB 1

Eyebrow light – LED PCB 1

The other end looked more reasonable:

Eyebrow light - LED PCB 2

Eyebrow light – LED PCB 2

The white SMD LEDs draw 300+ mA at 3.6 V, so they’re obviously depending on external current limiting provided by the regulator PCB, sporting a TLE4242 linear current regulator and a handful of passives:

Eyebrow light - Regulator PCB

Eyebrow light – Regulator PCB

AFAICT, they didn’t use the chip’s PWM control input or its LED failure status output.

Extracting the various PCBs from the wreckage and reconnecting the wires produced a satisfactory result:

Eyebrow light - resurrection

Eyebrow light – resurrection

The regulator limits the LED current to 120 mA at any input from a bit over 7 V to well past 12 V, with each LED dropping 3.0 V.

Dunno what I’ll use this junk for, but at least I know a bit more about eyebrow lights. The chip date codes suggest 2010 and 2012; perhaps linear regulators have become passe by now.

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