Trailer Wiring Question - Diff between hazards and brakes?

[davepl]

I'm trying to build a hidden LED strip for the back of my truck that does signals, brakes and backup lights. I have it all working in software, but when I went to wire it I ran into an issue:

On the 7-pin trailer connector, other than the electric brake, there's not a line for "Brake". Just park lights, left signal and right signal.

What I'm wondering is how do I know if the user has hit the brakes or turned on the hazards? In both cases it would seem that both rear signals light up at the same time. But that's the same as braking.

As it stands now I was thinking that I'm going to wind up a system that, when either the brake or the hazard is on, assumes it brake. I'm thinking I have to conclude braking when both the left and rear signal are on.

Is there something I'm missing? Some other way to tell hazard from brake at the connector?

[jkeady]

So you have a couple of things to think about here. Do you need a full 12v+ to activate your LED brake light system? If not, you could get power off of the trailer brake signal if you have a brake controller in your rig.

The second challenge is, a lot of trailer brake controllers are wired so they come on with the hazard lights on (just because they are getting a signal from the brake light switch and that circuit goes high with the hazards on). There are devices sold called pulse eliminators (probably similar devices with other names, too, which I suspect are just big diodes) that keep power from the hazard switch from feeding back through the brake controller and that keeps your trailer brakes from being actuated while your hazards are on.

If you don’t have a brake controller OR if you need a full 12+v to activate your LEDs, you’re going to have to run a new wire from the brake light switch and isolate it from the hazard light switch as mentioned above. OR you could add a second brake light switch to the pedal and build a totally separate circuit. Clear as mud?

[davepl]

Yup, that's what I was afraid of! So I'll treat both turn signals coming on at the same time as a brake, and if you want hazards or police lights, those are separate hookups.

[Grumpy old man]

Ebay $15.50 with free shipping 60" plugs into trailer wiring .

[davepl]

Yeah, I ordered one, it's sitting on my workbench, complete garbage. I have no plans to go into production, but trust me, big difference!

Anyway, I was thinking that the following logic is true, is it not:

1) If both signal lights are on, call it braking
2) Braking ends ONLY when both signals clear
3) If one signal cycles after braking, show brake AND signal

Am I missing anything obvious that would prevent it from working?