Turn signal circuit help..

Hello all,

I am in the process of building an Arduino and WS2812b powered trailer light setup with turn signals, brake, reverse light as well as cool effects. The issue I am having is my truck has combined brake/turn signal lights and the logic in the code requires a separate input for each signal i.e brake, left turn, right turn as well as running and backup lights. I have the later but again the combined turn and brake lights is causing some confusion in my brain. Any circuit help or ideas would be appreciated, thank you .

As I've never seen (in real life) a combined turn/brake light can you describe it a little better?

Mike.

Pommie said:

As I've never seen (in real life) a combined turn/brake light can you describe it a little better?

Mike.

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On a lot of cars, and on just about all trailers, in the US, there is one bright red light on each side of the car, which is used as both a turn signal, when flashing, and as a brake signal, when not flashing. Trailers can be connected with just 4 wires - ground, tail lights. left turn/stop and right turn/stop

Rescue1 said:

Hello all,

I am in the process of building an Arduino and WS2812b powered trailer light setup with turn signals, brake, reverse light as well as cool effects. The issue I am having is my truck has combined brake/turn signal lights and the logic in the code requires a separate input for each signal i.e brake, left turn, right turn as well as running and backup lights. I have the later but again the combined turn and brake lights is causing some confusion in my brain. Any circuit help or ideas would be appreciated, thank you .

Click to expand...

There are converters that you can buy:- https://trailerlightconverter.com/

You should be able to put some logic into the code to interpret what the truck is doing. It will need to store the previous condition of the lights, as it can't just work from the current state of the lights.

For instance if the left light is on, and the right light is off, that could mean that the truck is indicating left, or it could mean that the brake is on and the truck is indicating right. To work out the difference, the previous state, from about 1/3 second earlier, will tell you what is happening. In that case, if the previous state was both lights off, the truck is indicating left and not braking. If the previous state was both lights on, the truck is indicating right and not braking.

It is very difficult to get decoding perfect. If the brake it repeatedly pressed and released, that will produce exactly the same signals as when the hazards lights are on.

An alternative is to find the connections on the car for separate turn signals and stop lights. The centre high mounted stop light won't have any turn signal function, and the side repeater indicators on the front wing / mirror won't be affected by the brakes.

Diver300 said:

On a lot of cars, and on just about all trailers, in the US, there is one bright red light on each side of the car, which is used as both a turn signal, when flashing, and as a brake signal, when not flashing.

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From what you say, any change that happens simultaneously on both sides must be related to brake lights, and any change that happens on only one side must be indicators.
That should be simple to do in the Arduino code.

I'd provide a good debounce on the signal inputs, say 10 to 20mS, and allow a time window for changes to be classed as simultaneous, something like eg. 50mS?
That is to allow for relay contact bounce and noise, plus different relays operating at slightly different speeds.

rjenkinsgb said:

I'd provide a good debounce on the signal inputs, say 10 to 20mS,

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More like 50 ms for the debounce. The slow response time of incandescent filaments hides a lot of contact problems.

ak

You don't have front brake lights, so use the front left and right as turn signals and flash.
I think I would tap into the brake switch for the brake signal or the third brake light if the car has one.

KeepItSimpleStupid said:

You don't have front brake lights, so use the front left and right as turn signals and flash.
I think I would tap into the brake switch for the brake signal or the third brake light if the car has one.

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If it is trailer-mounted lighting, there is quite an advantage in using something that plugs into the trailer socket.

Diver300 said:

If it is trailer-mounted lighting, there is quite an advantage in using something that plugs into the trailer socket.

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There should be lots of commercially available converters and their are multiple trailer sockets too.

Below is the LTspice simulation of a circuit that, I think, does what you want: (discussed here):
The circuit requires two IC packages (4001 and 4030) plus associated discrete parts.

Since you don't need to drive lamps, you can leave out the MOSFETs and directly use signals NL, NR, and NB.

Note that these signals are active low. so you need to allow for that in your program.