vehicle - filter out brake signal.

Thread Starter

Jo Bee

Joined Feb 9, 2024
3
Hello,

I have a vehicle that shares the same Brake signal as the turn signal. I just need to filter out the Brake and only output the flashing turn signal. I can tie the brake light to the 3rd brake line. any help would be appreciated. Thanks!
 

strantor

Joined Oct 3, 2010
6,798
I read that like 5 times and still not sure what you're asking. That probably says more about my reading comprehension than your writing skills, but if you ask again with a different combination of words we might make progress.
 

geekoftheweek

Joined Oct 6, 2013
1,221
What do you need to do exactly? One of the easiest ways of accomplishing this is to tap into the front turn signals. If you are trying to alter the operation of the rear lights obviously that isn't going to be any help.
 

Thread Starter

Jo Bee

Joined Feb 9, 2024
3
My apologies, so to explain it better. The tail lights on the car have is only one light. When you brake the light is solid. when you turn the signal on, it will flash. I'm installing a set of aftermarket tail lights. on the taillights themselves the brake line and turn signal from the vehicle harness will only turn on the turn signals. So when I brake, the turn signal will light up once and turn off. when the turn signal is on, then it will flash. i can setup the brake line to turn on the brake light. but how do I filter out the brake line signal so it doesnt interfere with the turn signals. Hope that makes sence.
 

crutschow

Joined Mar 14, 2008
34,464
I have a vehicle that shares the same Brake signal as the turn signal. I just need to filter out the Brake and only output the flashing turn signal.
Funny you should ask, but I just happen to have a circuit that should do that (LTspice sim below).
It's not simple, but the only way I know of to possibly simplify it would be to program a microprocess for the task.

The green trace is the simulated combined brake & right turn signal (b+r), and the yellow trace is the combined brake & left turn signal (b+l) .
The red trace is the decoded right turn signal, and the blue trace is the decoded left turn signal.
The purple trace is the decoded brake signal, if needed.

So how are you at doing a breadboard circuit of this complexity?

1707529024724.png
 

Thread Starter

Jo Bee

Joined Feb 9, 2024
3
Ive never made my own circuit before. But I'm an excellent solderer haha might need a lil help to build this. So is there one I can just do for the single left or right side? seperate harnesses?
 

crutschow

Joined Mar 14, 2008
34,464
So is there one I can just do for the single left or right side? seperate harnesses?
Don't offhand see how to do that.
How would you know when the brakes are active when looking at only one side that has its blinker on, since that blinker light looks the same whether the brake is on or not?
You also have to look at the other side with the steady brake light to know.
 

strantor

Joined Oct 3, 2010
6,798
My apologies, so to explain it better. The tail lights on the car have is only one light. When you brake the light is solid. when you turn the signal on, it will flash. I'm installing a set of aftermarket tail lights. on the taillights themselves the brake line and turn signal from the vehicle harness will only turn on the turn signals. So when I brake, the turn signal will light up once and turn off. when the turn signal is on, then it will flash. i can setup the brake line to turn on the brake light. but how do I filter out the brake line signal so it doesnt interfere with the turn signals. Hope that makes sence.
Ok I get you now, thanks for the clarification. I think you will need to separate these three signals (left blinker, right blinker, and brake) in the existing wiring harness. "Filtering out" as you propose is not simple or fool proof. For something safety related like brake lights you really want fool proof. You need to find where the brake switch is on your car and where its signal goes. Find where that signal merges with the lights circuit and disconnect it, run it just to your new brake lights. Then your turn signals should only come on when the signal is selected, not also when brakes are pressed.
 
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