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Isolating constant from flashing signal

Wicked SC

Mar 23, 2021
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Hello, guys. Totally new guy here, so sorry for the rookie question. Any help is greatly appreciated.
I am working with an automotive 12V DC circuit. I have a BCM that sends a flashing voltage (turn signal), or a constant voltage (brake lights) to a bulb via the same wire. I am trying to eliminate the brake signal, and use this bulb as a turn signal only. Is there a way to "filter out" the constant 12V when the brakes are applied, but allow the flashing signal to reach the bulb for turn signal?
I would imagine reprogramming the BCM would be the easiest way to do this, but I have no access to the hardware or software to do it. Can it be done externally, such as with relays or SS devices?
 

Martaine2005

May 12, 2015
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What happens if you are braking and indicating?
Surely, the bulb has two filaments?

Martin
 

Harald Kapp

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I would imagine reprogramming the BCM would be the easiest way to do this, but I have no access to the hardware or software to do it.
It is good that you can't do it. There are huge safety risks involved and you almost certainly will lose the license for using your car on public roads.
The "easiest" way (what is easy, what is hard is a matter of your capabilities) would be to feed the signal to a microcontroller, have the software in the microcontroller check for the duration of the signal. If it is steady for a period longer than the pulse period of the blink signal, do nothing.
If the signal shows changes within a time span a tad longer than the blink signal's period, activate an output to allow blinking (use an additional relay to pass the blink signal to the bulb).

But why for goods sake do you want to de-activate the brake signal? That is a vital indicator!
 

Martaine2005

May 12, 2015
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Hehe, good ol' US OF A.
They spell and pronounce English words incorrectly, drive on the wrong side of the road AND have red turn signals!.:p
There is a simple way to do this but.........
Is this vehicle being used on the road?
And IF you eliminate the brake signal, what other option do you have for brake lights?

Martin

 

davenn

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I am trying to eliminate the brake signal, and use this bulb as a turn signal only. Is there a way to "filter out" the constant 12V when the brakes are applied, but allow the flashing signal to reach the bulb for turn signal?


As the others aske ... why? if for a vehicle on the road, totally illegal to do ... public roads, race tracks etc


of some sort of offroad use where no one would be following you ..... no reprogramming necessary ...

But before I give you the easy answer ... AGAIN, WHY do you want to do this ??
 
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