Modifying turn indicators so that they can also act as DRLs

Discussion in 'Automotive Electronics' started by Tamrat Assefa, Dec 13, 2017.

  1. Tamrat Assefa

    Thread Starter New Member

    Dec 13, 2017
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    Hello people of AAC, I just joined here. I am Tamrat and I am from Ethiopia. I need assistance on modifying my 2009 Toyota Yaris Hatchback so that I can use the turn indicators as DRLs.

    I have always been fascinated by Ford's and Chevrolet's similar implementation of dual purpose bulbs on the brake lights (brake lights also double as turn indicators). And I am also a huge fan of Daytime Running Lights. Unfortunately my car, a 2009 Toyota Yaris, doesn't come with DRLs from factory. I was on the process of adding LED strips as DRLs when I noticed something. Some cars (like the Toyota Tacoma pictured below) have turn indicator bulbs that also act as DRLs. The bulbs are on when the car is running and the respective side will blink (flash) when a turn indicator signal comes. I tossed away the LED idea and started to look into it more to get it for my car.

    [​IMG]

    At first I thought it was very simple. My idea was to get a line that is hot when the car was running, and wire the turn indicator bulbs so that they can stay on. Then I will use another relay to turn off the lights when a turn indicator signal came (hence creating a flashing effect). I used to be an Electrical Engineering student before I dropped out and switched to Software Engineering so I had tools like MultiSim that was given to me from school. I tried to create a simple circuit that would achieve this (pictured below). But even with very minimal knowledge of circuits, I noticed a lot of things that will not work (or not ideal).

    [​IMG]

    Problems I noticed:
    1. The front indicator bulbs will not be in sync with the rest of the bulbs (side and rear) because the ON signal will turn them off. Not ideal.
    2. If the DRL is switched off from the main switch (SWITCHA | Key = D), the indicators will not work at all.
    3. If the engine is off (hence DRLs OFF), the front bulbs will not light up at all if I try to use the hazard warning lights.
    I'm sure there are more issues with this design. I'm not even sure if I can turn on a single bulb with out affecting the other two.I have attached the electrical wiring diagram from the turn indicator and hazard lights. I need assistance on how to achieve this and eliminate the issues I stated above.

    Thank you very much for your time,
    Tamrat
     
    Last edited: Dec 13, 2017
  2. Tamrat Assefa

    Thread Starter New Member

    Dec 13, 2017
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    Here is the wiring diagram. For some reason, I can not attach it to my main post.

    Tamrat,
     
  3. Reloadron

    Distinguished Member

    Jan 15, 2015
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    I believe what you will discover is that the turn signal and hazard lights are all driven by a fairly complex module which is the gray shaded portion of your attached file. That module even communicates with the ECU so for example if you forget to turn off a turn signal after a set period with no braking and a certain time and distance you get a warning the turn signals were left on. This also controls the alternating flashing effect between rear/front and the sides. Personally I wouldn't screw with it because I would bet if you inadvertently back feed it and something "bad" happens it could be a few hundred dollar lesson. You would need to know everything about that module which is likely a heck of a learning curve. However, you are free to do with it as you wish but I would not screw with it. Gone are the days of "simple" in anything automotive electrical.

    Ron
     
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  4. Tamrat Assefa

    Thread Starter New Member

    Dec 13, 2017
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    You're right. Everything is so complex these days. The miniaturization is more annoying than the complexity. And I am well aware of the risks involved. I'm doing lots of research and asking a lot of people before attempting anything to the circuits.

    The 8-pin flasher relay Toyota is using here is kinda alien to me. I have tried to look for diagrams on how it works but not much info so far. That's why I'm trying to fiddle with the wires that leave the relay, not the relay itself. I'm just looking for ideas, better ones from what I have proposed.

    Speaking of ideas, here is one I just thought of. The flasher unit sends pulses of 12V signals to the bulbs to light them right? So what if I just add 12V to the positive line to power it constantly? Then convert the pulsing signal to a steady signal through some sort of mechanism, and that steady signal can be used to turn off the DRL. This way I think I can keep the OEM setup intact and working as intended but just add a bit more to it. I can prevent backfeeding with diodes right? And I think its possible to convert the 12V-0V-12V pulsing signal to something like a steady 9V signal using capacitors, right?

    What do you think about this?

    Tamrat,
     
  5. Reloadron

    Distinguished Member

    Jan 15, 2015
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    You could try it as long as you aren't worried about anything going poof. Diodes are always a popular blocking mechanism. I played a similar game on my bike, a 92 Harley Electroglide. I went from standard incandescent lamps to LED. Looking for a flasher and there is none. When going to the lighter load LEDs you need to add some load. I also discovered there is no simple flasher but rather a module which has a speed input and timing function. I never would have thought in 92 they were using a module.

    Anyway, I guess you could work from what you have and try a few things. Drawings like what you have will show a module but finding out what is actually in these modules is borderline impossible. That has been my observation anyway. Hopefully a member who is really good with automotive will come along and be of more help than I can be.

    Ron
     
  6. Tamrat Assefa

    Thread Starter New Member

    Dec 13, 2017
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    Yeah, I have given up on the figuring out the flasher relay. So I tested the terminals at bulbs. Unfortunately removing a bulb will send the module into a hyper flashing mode and I couldn't get an accurate reading.I tested the two wires against ground and one terminal read 0V at all times. I assumed that was the ground feed. The other switched from 0V to about 9.7V and repeated like that. (I think) My multimeter didn't have enough time to update the displays (due to the hyper flashing) but I think the max value is 12V. So we know for sure there is a pulsing signal that's fed to the bulbs.

    Here is the rough sketch of the setup I'm thinking about now:
    [​IMG]

    I'll try to simulate this and see the results. In the mean time, can you see anything wrong with the sketch? Obviously I have to dig into my old lecture notes into RC ciruits to build the converter. Suggestions are appreciated!

    Thanks,
    Tamrat
     
  7. Reloadron

    Distinguished Member

    Jan 15, 2015
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    That's how I would try it. :)

    Ron
     
  8. dl324

    AAC Fanatic!

    Mar 30, 2015
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    I'd just turn on the headlights; and remember to turn them off when the engine isn't running.
     
  9. Tamrat Assefa

    Thread Starter New Member

    Dec 13, 2017
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    :D:D:D I am currently using that hack. But like I said in my first post, these dual purpose bulbs fascinate me. I have made it my mission to get them on my car. Plus I forget to turn on the headlights a lot of the time (turning off is easy, there is a warning beep). And the fact that the headlights are too bright and I get a lot of complaints from other drivers. And...and the fact that I want the indicator bulbs to wear out than the headlights which are much more expensive. Last but not least, these kinda things teach you a lot, more than anything.

    Almost forgot it....there are like a billion Yarii (plural for Yaris? o_O) and mine will be truly UNIQUE. :D:D:D:D

    Tamrat,
     
  10. bwilliams60

    Well-Known Member

    Nov 18, 2012
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    Look on the side of the relay for the schematic for it. If nonthere, buy another one and open it up and reverse engineer the rest of the diagram. I dont think there are any magical electronic gremlins in this circuit so you should be okay. Does your transportation industry allow for such modifications to lighting systems?
     
  11. Tamrat Assefa

    Thread Starter New Member

    Dec 13, 2017
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    I have tried to look at the relay, but not much info is available for it. That's why I left the relay alone. Getting one to 'reverse engineer' might be useful to see the internals and how it works but I don't think I can modify it much because its such a small unit and it probably has some kind of digital board.

    As for my government and such modifications: not much attention is given to such modifications. As long as your headlights are ON by night and your turn indicators work, you're fine. The only modification that's not allowed is window tints (not percent based, ANY kind of tint is illegal).

    Update on the circuit: with the help of an old friend from Electrical Engineering school I was able to build a simple circuit that converts the pulsed 12V signal into a steady signal with simple capacitor and an op-amp. I tested it inside MultiSim and it works. Only problem is there is a slight delay (like 0.5sec) before the signal is converted from pulse to steady and due to this fact the relay turns off the DRLs like a 0.5sec too late. The simulation shows the bulb being fried (I think that's whats happening: it sort of ceases to exists, the bulb filaments disappear :D).

    So more fiddling, more fine tuning. Then I'll buy parts tomorrow or the day after that and wire everything on the bench and test it out. Suggestions are still welcome. Will keep you updated!

    Tamrat,
     
  12. Tamrat Assefa

    Thread Starter New Member

    Dec 13, 2017
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    UPDATE:

    Just waiting for my old friend to send me refined diagrams for the whole thing. While I was on that, I started going through the detailed documents on the car and found another interesting thing. And I feel stupid for not thinking about it before.

    [​IMG]

    TL and TR leaving the Headlight Dimmer Switch are really interesting. But the wiring diagram doesn't say about the voltages/currents across/through these terminal. Time to open up the steering column and run some tests. Excitement! :D

    Tamrat,
     
  13. eetech00

    Active Member

    Jun 8, 2013
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  14. Tamrat Assefa

    Thread Starter New Member

    Dec 13, 2017
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    Hello eT and thanks for the suggestion. I have looked at that exact thread before when I was researching this. I basically wanted to get what the Tacomas had. I found out that if I bought a new headlight dimmer switch and a running light assembly relay, I could get a factory DRL (some Yaris have them). But the problem with that was, the DRL used either the low or high beams at half the voltage.

    UPDATE:
    Went out and opened up the steering column to measure voltages at the headlight dimmer switch (the headlight stalk). All excitement was wiped away when I noticed that I have lost my red multimeter probe. Bummer. Gotta wait till tomorrow to get new ones (or borrow from a friend). :(:(

    Tamrat,
     
  15. Tamrat Assefa

    Thread Starter New Member

    Dec 13, 2017
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    Hello guys, UPDATES!

    So I removed the steering column cover and took a look at the headlight dimmer switch (integrated into the headlight stalk). It has about 11 pins. I tested the harness side for voltages going into the switch and I have isolated two wires responsible for the turn indicators (TL and TR as shown in the diagram I shared couple of posts ago).

    Both TL and TR have constant 12V feed going into them (probed across the terminals and body ground) at all times, even when the ignition is OFF and key is removed. When the switch is moved to the left indicator position TL's voltage will drop 0. And when the switch is moved to the right indicator TR's voltage will drop to 0. I have deducted that these two lines can be used to control the state of the turn indicator bulbs individually. I have also found a line that gets 12V when the headlights are being used (can be useful to turn the DRLs off at night). Last but not least I have found a line with 12V when the ignition is at ON (will be used to power on the DRLs).

    Since TL and TR have 12V at all times, they can be used with relays to keep the DRLs on. When either of the two loses power (when turn indicator is used) the relay will become open and DRL will be off. Turn indicator on the respective side will blink. Hopefully this implementation will work this time. I'll try to simulate and confirm.

    Tamrat,
     
  16. Tamrat Assefa

    Thread Starter New Member

    Dec 13, 2017
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    Left this idea alone for some time because I was focusing on school. Back at it now.

    I have 3 12V SPST normally open relays now. Genuine second hand DENSO ones. Planning to wire the whole thing today. But I have one big question. I am basically adding a circuit on top of the OEM wiring. The circuit is more or less isolated from the OEM wiring and will not interfere in any way. I'm just tapping into factory wires to get signals. I don't have to worry about feeding the OEM circuit with current except at the point where I tap into the bulb wires.

    Do I really need to be concerned about backfeeding (to the flasher unit relay in this case)? Or are these cars clever enough to deal with that on their own? And what kind of diode should I use if I have to handle it myself?

    Thanks,
    Tamrat
     
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