This is not a typical flashlight related post, but it does require general LED knowledge that many users here have. I am asking this here, because the car forum I frequent is rather dead.
TL:DR I would like to know how does a tail light get signaled to different brightness. Meaning, when the car tail light is on, it is not super bright, but when the brakes are applied, it lights up brighter.
long version.
I am trying to install an aftermarket brake light that’s part of the after market bumper. like this.
I would like to take draw the current from existing tail light harness. I tried to find a fuse that says “brake” or “tail light” but none to be found. I guess it is because it is LED, no fuse is required or its fused all as part of another system.
I was able to identify at least 2 leads that was giving 12v, and 1 lead that draw 2v. Both light up the light I want to use, obviously, the 2v was very dim, and none of them work with braking. As I tested, I can see the other tail light working, that’s how I am able to tell.
Yeh, most have extremely annoying PWM. Same as “daytime lights” in front. If you turn your head quickly you can see the annoying “dotted lines” as the image sweeps your retina.
If you got a CHMSL, try hooking into that, as it’s only on when the brake-lights are on.
But with my BAY15D LED attachments, the 12v was always on then the other 12v is a signal input to control low or high. (on a traditional light its just 2 different filament)
so could the 2v be a signal input for a running 12v?
On early LED taillight cars, PWM was definitely used. I vividly remember driving behind Cadillac cars with them, and when moving my eyes side-to-side scanning traffic the “PWM echo” would happen. Very annoying. They continued to use PWM for many years, until finally… don’t see it any longer.
There may be some kind of voltage attenuation technique for dual purpose LED module (parking and brake). I’d thought maybe micro LED’s interlaced, where some rows would be activated when brake lights are pressed. Most automotive companies take the easier, more logical way out — two sets of LED’s, one for parking, one for brake.
almost certainly is, they may change frequency of pwm, but pwm is still used, nowadays cars do not use tons of power wires, they use modules with 1 power and signal running to it, and it distributes power to whatever the module is responsible for, locks, windows, lights…. in old cars all switches were power switches, today, all are low current signals, to modules.
my dashcam sees pwm, whenever i look at the recording, i see cars passing with tail lights\drl strobing.
Thank B’harni (pbuh!) mine has LED-array brake lights, but hotwire bulbs for turn and reverse. Replaced both of those with hella-bright amber and white LED bulbs, respectively.
