Trailer Lights Logic

I fear there might be an error in your truth table.

Is this what it should be.??

On the 3rd and 4th rows you had the Left and Right Orange outputs swapped.

Mark

Right, that's the tricky part. When the brakes are on, and an indicator light is blinking, you need to reverse the state of the correct indicator.

Imagine braking: both tail lights are on.

Now turn right while the brakes are on (like at a stop light waiting to turn) - the left light stays ON while the right light turns off and on.

I thought that as well ...but

Your truth table should be showing the state of the input, not what the lamp was doing. ...

If the view is from the rear of the trailer, then I can see some merit in matching the red light of the car to the orange light ... which it does.

BUT when the brake is On as well there is this red light that is ON plus this orange light flashing, so is having it match the towing vehicle a bonus or a distraction ???

Imagine a long line of cars turning, the indicators are all flashing at different rates and some are on while others off.

It isn't confusing.

The other small part of this is that with the left indicator on and the brake, the left lamp toggles state, but the right one stays ON.

If the left indicator is on by itself the left lamp toggles but the right stays off.

ie the bit you need to detect is the toggling bit.

Yes I still haven't sorted the internal logic and the housing mine came is seems to be expoxy .....

Mark

I think it toggling in reverse to what the car is doing is ok. Otherwise the logic just gets more complex than it needs to be.

It'd be great to test out what the commercial module does, and how it handles all the states.

Did you try out the circuit at: https://simulator.io/board/qQCIfvpreQ/3   ?

(edit: click on the zeroes beside the words "left" and "right" to change the input states)

It seems to work properly for all situations. Except that the hazard lights (4-way blinkers) flash the red brake lights on and off. But I don't think there's a way around it unless we keep a logic state related to previous state.

ps, keep in mind that the circuit simulator misses the bit at then end - when both inputs are off, power to the circuit goes off and the whole thing resets (in the simulator you'd need to press reset when both inputs are off)

Thanks,

-Nico

I think it toggling in reverse to what the car is doing is ok. Otherwise the logic just gets more complex than it needs to be.

It'd be great to test out what the commercial module does, and how it handles all the states.

Did you try out the circuit at: https://simulator.io/board/qQCIfvpreQ/3   ?

(edit: click on the zeroes beside the words "left" and "right" to change the input states)

It seems to work properly for all situations. Except that the hazard lights (4-way blinkers) flash the red brake lights on and off. But I don't think there's a way around it unless we keep a logic state related to previous state.

ps, keep in mind that the circuit simulator misses the bit at then end - when both inputs are off, power to the circuit goes off and the whole thing resets (in the simulator you'd need to press reset when both inputs are off)

Thanks,

-Nico

Did you try out the circuit

No for a few reasons.....

I also fell into the trap of the latched brakes staying on for a full cycle of the indicator until the power drops out the latch.

I initially thought that was wrong and wouldn't work until I realised it was only half a cycle and who cares.

I suspect some of the bits can use an SCR since they latch and have good current capability.

It'd be great to test out what the commercial module does, and how it handles all the states.

I was thinking the same thing the other week about building a test rig.

I got asked to build another unit that does the reverse (combines 4 wire plus tailights, to 3 wire) for LED's, and thought I should build a test rig ...

Looks like I have a job this afternoon, but it may be next week as I'm heading away for the weekend..

I'll use relays and a uP.   

mark

PS I did this table

ntewinkel

I wonder if this will do what you want.

/*

      Trailer Lights

   Pin assignments
   Pin 0  Rx
   Pin 1  Tx
   Pin 2  
   Pin 3  Left Indicator      (HIGH)
   Pin 4  Right Indicator     (HIGH)
   Pin 5  Left Out
   Pin 6  Right Out
   Pin 7  Brake Out
   Pin 8
   Pin 9
   Pin 10 
   Pin 11
   Pin 13 Led
   
   Created 17 Mar 2017
   by Mark Beckett

   Version
   0.1  Initial Code  started 17 Mar 2017

   Function
   This interfaces between an American 3 wire light system and converts to 4 wire for a trailer.
   The 3 wire system uses the same light for Brake and Indicator, while the 4 wire seperates the Brake and Indicators.

   Requires regulator and solid state switching.
   Inputs need a resistor and zener to drop to 5v.
   
   ---------------------------------------------------
   To Do :
    
  
   */

  #define TailLEFT 3                // LEFT Tail light input
  #define TailRIGHT 4               // RIGHT Tail light input
  #define OutLEFT 5                // LEFT Indicator Output 
  #define OutRIGHT 6               // RIGHT Indicator Output
  #define OutBRAKE 7               // BRAKE light Output

  boolean  TailLEFTstate = 0;
  boolean  TailRIGHTstate = 0;
  boolean  BRAKEstate = 0; 
    

void setup() {
  // put your setup code here, to run once:



  pinMode (TailLEFT, INPUT);
  pinMode (TailRIGHT, INPUT);
  pinMode (OutLEFT, OUTPUT);
  pinMode (OutRIGHT, OUTPUT);
  pinMode (OutBRAKE, OUTPUT);
}

void loop() 
{

    TailLEFTstate = digitalRead(TailLEFT);
    TailRIGHTstate = digitalRead(TailRIGHT);
    
    if(TailLEFTstate == 1 && TailRIGHTstate == 1)
    {
      BRAKEstate = 1; 
    }
    
    if(TailLEFTstate == 0 && TailRIGHTstate == 0)
    {
      BRAKEstate = 0;
    }
    
    digitalWrite(OutBRAKE, BRAKEstate);
    digitalWrite(OutLEFT, TailLEFTstate);
    digitalWrite(OutRIGHT, TailRIGHTstate);
  
 }

I'm picking that a diode from Left and Right Brake/Ind is enough for power.

Use a 7808 to give 8v into an Arduino ( Digispark with start delay removed ... maybe ).

You'll need to use a resistor and 4.8v zener across each input to drop it down.

Perhaps a MosFET between the Left/Right vehicle tailight to drive each Indicator.

With another MosFET using the diode common to power the brake lights.

Mark

edit ... minor cut and paste in pinmode.

That looks perfect, thanks!

I had thought about using a Digispark minus start delay - I remember looking that up.

I like that the microcontroller gives a LOT of flexibility in maintaining states and doing additional logic that would be hard to do in hardware.

But I do like that the 4000 series chips can handle the higher voltages directly.

I might have to try both. Makes for good science

-Nico