Logic circuit third brake light.

[mneary]

I have never seen a car with the turn signal light the same as the brake light. They are always separate.

Maybe you should get out more.

 

[crutschow]

That circuit lights the 3rd light only when both inputs are on.
If the inputs were brake-light-only, there would be no need of the circuit: it could be replaced by two diodes

Don't even need the diodes.

 

[Wade Hassler]

Here ya go: 1995 Dodge Dakota

Lots of pickup trucks have the bare-minimum of colored plastic in the rear corners.
I can't give you numbers because it's not something that's indexed (as far as I know: prove me wrong, Internet!)

Admittedly, they're getting rarer... and apparently about to disappear
https://www-nrd.nhtsa.dot.gov/Pubs/811115.PDF
... says that amber turn-signals are 'slightly better' at preventing rear-enders than are red.

All the US manufacturers would need to do is equip the domestic production same as the exported.

 

[audioguru]

A pickup truck is missing many safety features that are used on cars. There isn't much space for rear lights so they simply combine them on each side.
The lights will be useless anyway when the truck barrel-rolls.

 

[Wade Hassler]

Here's another circuit that might suit:

 

[crutschow]

Here's another circuit that might suit:
View attachment 41403

That circuit will blink the 3rd light when the brake is applied and a turn-signal is blinking. You want a circuit that will maintain the 3rd light steady under those conditions, thus you need a memory circuit with some type of latch, such as I previously posted or the Third Brake Light SCR circuit that Tricky posted.

 

[nsklavos]

Whoops, had wrong circuit before. This is the one I meant.

**broken link removed**

 

[crutschow]

I think it's just an OR Gate Function

Actually, it's an AND gate. Both inputs have to be high for the lamp to light.

 

[xpi0t0s]

You can't solve it with a simple circuit based on just the signals from the lights: the truth table shows why:

L R C
0 0 0
0 1 ? is this brakes on+left blinking/off, or brakes off+right blinking/on?
1 0 ? (similar)
1 1 1

L=left brake/indicator
R=right brake/indicator
C=centre brake light

But if you feed the brake light back into the inputs then you can (I think) solve it from this truth table:
L R C'C
0 0 0 0
0 0 1 0
0 1 0 0
0 1 1 1
1 0 0 0
1 0 1 1
1 1 0 1
1 1 1 1

C' is the previous state of the centre brake light, so this is just LR+LC'+RC'.