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EU brake light vs US

Discussion in 'Roadster: Technical' started by ravng, Apr 8, 2015.

  1. ravng

    ravng Member

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    Hi guys.

    In another thread some time ago I read with interrest that the US roadsters turns on the brake light while braking with regen, while the EU cars does not.
    Apparantly this has to do with some older EU regulations that stated that only physical use of the pedal was to turn on the light. I guess this has changes since then, because the Model S in EU turns on the light.

    I talked to Tesla service center localy about this, and they confirmed this behavor (they confirmed that EU cars does not turn on the light, they did not know the reason). I asked then if this was an easy software fix to enable this feature (because this is something I really want, regen stops the car very quickly and it's easy for the car behind not to notice), but they told me that if the car came without this function is was not possible to enable it.

    But I am hoping there is some hack for this, does anyone know or have a good idea?

    If not I might need to figure out something myself (maybe an accelerometer connected to a relay?).
     
  2. Mattias

    Mattias Member

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    #2 Mattias, Apr 8, 2015
    Last edited: Apr 8, 2015
    Sure it could be possible to do a DIY-retrofit, but I wouldn't like hacking into the main loom, warranties and so on...
    It would also most certain have to involve an accelerometer, since the throttle is electronic and you would need an on/off signal wire from somewhere. Maybe you could splice into the Car's potentiometer inside the throttle, obtain a resistance value, and use this via some "controller" to control the brake light. But this would also mean that the brake light is turned on all time, when the throttle isn't being depressed. Never heard of someone doing this before :)

    Remember almost all cars in Europe are manual geared and none of them turns on the brake light when you lift off in gear, even if you were in 2nd gear doing close to 100 km/h!
     
  3. ravng

    ravng Member

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    Problem with EV's is that you almost never touch the brakes (at least if you want to maximise the range) and use the regen to deaccelerate when you get close to a intersection, in the roadster this deaccelleration is quicker than you normaly get when you lift on in gear in a ICE car (normally you will not be in 2 gear at 100 km/h :)
     
  4. Mattias

    Mattias Member

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    Yes, it was just an extreme example :)

    Anyway come to think of it, here's how I would do it.

    1.
    Get an Analog/Digital controller (I think an Arduino would work)
    2.
    Obtain an Analog feed from the ABS-sensors (this indicates your speed)
    3.
    Obtain the secondary feed from the Variable Resistance in the throttle (Potentiometer)
    4.
    Feed these to the Arduino controller
    5.
    Write the necessary code to make the controller enable the output (brake lights) to turn on only when it has an active input from the ABS-sensor and a throttle position which indicates the throttle is not being pressed.
    6.
    Use a small relay, or better something solid state, like a ssd relay to control the current flow to the lights.
    7.
    Mount an appropriate fuse! :)

    The hard part here is writing the Arduino code, not sure about that.
     
  5. ravng

    ravng Member

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    I program MCU's like the atmega328 (same as arduino) daily at work so thats not a problem.

    I was thinking about a mutch easier design, limited to just run the "extra" brake light (better than non).
    Accelerometer connected to an atmega with a relay, mounted inside the lamp.
    Then connecting the existing breaklight to the COM on the relay, feed from the car harness to the N.C. pin and permanent power on the N.O pin.
    So whenever the accelerometer/atmega triggers the relay it gets it's power directly from 12 volt. If the car triggers the light it is feed truh the N.C. connection. This solution makes a physical seperation between the car brake circuit and the hack and prevents that 12 volt is feed back into the car circuit. Also if there is something wrong with my hack it does not prevent the light from turning on. Additional permanent 12Volt can be feed from the interiour light, so don't need to run long wires.

    If both the car and the accelerometer triggers the light at the same time it does not matter.
    Then it's just a matter of tuning when the light is to be turned on.
     
  6. Mattias

    Mattias Member

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    I guess that would work as well, and accelerometers are cheap as chips on ebay.

    How about downhills, would it recognize it as braking and turn the lights on? Bumps, potholes and so on, this could also trigger the lights.

    I believe "my" method is more in line with what Tesla actually uses, but you are correct that using an accelerometer only would make the installation easier. It could probably work almost as good after a bit of configuring.
     
  7. ravng

    ravng Member

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    It might be a pain to configure. Good point about downhills.
    I have yet to play around with accelerometers (but I have one lying arond here somewhere). As I understand they have 3 outputs (x,y,z) so if it is mounted correctly I guess I only need to condsider one axis and that would work regardless of going down a steep hill or flat ground (will still move forward even if I also move downwards).
    One way to get the right values it is to have a button connect to it and "learn" it while driving. Holding the button when I want the light to be on and read out the values afterwards.
     
  8. EVenthusiast

    EVenthusiast Member

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    I thought I read somewhere that some vehicles (BMW maybe?) use the G force values to figure out if the brake light should come on (or make it brighter/flash). This should work even going downhill.

    That said, manual transmissions are very popular in Europe, so wouldn't people be used to engine braking anyways?
     
  9. Danal

    Danal electricmotorglider.com

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    Use a 3-axis chip, and smooth the data over time. VERY easy to tell stopping from bumps.
     
  10. supersnoop

    supersnoop Tesla Roadster #334

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    Based on my experience programming the ECU's in BMW's, I bet this would be a really simple programming change. I imagine it's just a software setting that would just need to be switched. I'd climb the ladder at Tesla to see if someone could eventually help you out. Of course, the problem will most likely be that very few people will have the skills, knowledge, and tools necessary to make the change.
     
  11. Mattias

    Mattias Member

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    Even if you were to use an accelerometer, wouldn't you still need a controller like the Arduino? Otherwise all the logic, computing and Input/Output would have to be inside one accelerometer module? Never seen that before.
     
  12. JohnGarziglia

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    Before going to all of this Arduino/accelerometer effort described above, I would check that there is not some unused or alternate output pin on whatever module controls the brake lights that is connected to the brake lights in the US, but is connected to another output pin in the EU. I have no idea which module or from where the 12 volt output for the brake lights come from but first I would try to determine that, and then see if there are any unused or unconnected pins on the same wiring harness. Just a thought.
     
  13. strider

    strider Active Member

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    I doubt there's any physical difference. I'm 99% sure it's a software setting. I would e-mail [email protected] (does that still exist?) and submit a feature request. If the law changed it should be simple to change the Euro firmware and offer the update as part of annual service.
     
  14. markwj

    markwj Moderator, Asia Pacific

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    My car was originally delivered without regen turning on the brake light. The reason was that supposedly the legislation required the brake pedal to be physically pressed for the brake light to be illuminated.

    After a few owners requested a review, Tesla checked the legislation here and decided that it was possible after all. So, a change was made in a 'low level setting' of the car, and the feature was enabled. My understanding is that this is not VDS DIAG level stuff, but rather connect a laptop and alter the settings deep in the firmware.

    Bottom line: Tesla can (or at least could) change this by a firmware setting. But, I guess they will only do that in compliance with local legislation. They are not going to turn it on for you if the law says it is illegal.

    - - - Updated - - -

    P.S. If you're going to go the DIY route, the way I would do it would be to use a little CAN controller capable microcontroller. The instrument CAN bus (1MHz available on that DIAG port in the passenger footwell) ID 0x400 should have what you need. That ID drives the speedometer instrument cluster, which includes the amount of regen the car is handling. Once that passes a defined threshold, turn on the brake light. See (teslaroadster_canbusnotes.txt) for a list of what has been decoded on the roadster. I've never gone looking for the Amps dial, but it is definitely in there. Most likely B1=0x01 sub-message in the last 4 bytes.
     
  15. ravng

    ravng Member

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    Markwj: Maybe possible feature for the OVMS, since the hardware is allready there? But regen might not be the best value, since this can change with battery capacity, temperature etc. How about the g-force meter?

    But I'll have another chat with the Tesla guys.
    Problem is that the local Service center does not have any experience with the Roadster. At my first visit all of them went outside to take a look at the car since they had never seen one before, hehe.
    There is just one american guy who previously worked at Tesla in California who has any experience with roadsters, and they don't have any parts localy.
     
  16. ernst

    ernst 't is een grijze.

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    Back in the day when I just got my tesla I asked in holland if the could switch them of when regen would kick in at my freshly imported 1.5. They told me sure we can do that, we can toggle it in the software settings in the computer and upload it to the car. Turend out the could not do it with the 1.5 only 2.X models. The could set the settings only the car would not take it. Anyway you could just asked the to take a look at there roadster configuration tool and see if the can find the setting to change it. Sound like the don't not have to much experience with it.
     
  17. ravng

    ravng Member

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    Yeah they still have no clue at my service station (but very nice guys, hehe)

    So first I got this forwarded answer in english:" The regulations for EU Roadster at that time/period was that the Brake lights would not be activated during regen, and only if the brake light was physically pressed would brake lights activate. The USA and Japan Roadster could have regen brake lamp set due to different regulations.
    During the introduction and manufacture of the Model S the EU regulations changed and the regen brake light is now required rather than prohibited "

    Followed by a norwegian text that translate something like "This is something we dont want to do due to EU regulations". eeeh, somebody somewhere must have missunderstood me. If it's now a requirement on new cars it's would certainly be ok to changed this on an older car.
     
  18. Chillout

    Chillout Member

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    All right guys, I found a solution.

    Directions for service employee who didn't have a clue:
    1.Connect to the vehicle’s OBD2 port or CAN 4 bus (Diagnostics bus) using the Gridconnect USB/CAN adapter.
    2.Open the diagnostic tools icon
    3.Open the Set Country tool and select the country that the car is primarily located in

    This screen will show:

    regenbrakelamp.png

    then it's a matter of selecting what you want.

    Enjoy, and please let me know if this worked.
     
  19. strider

    strider Active Member

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    Woah. So based on that screenshot it looks like I could just kill the TPMS all together? That thing is nothing put a PITA. Loses synch every few months. It's basically worthless so I wish I could kill it's bleating.

    No way Tesla would do this for me. What's required to do this at home?
     
  20. supersnoop

    supersnoop Tesla Roadster #334

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    I imagine you'd need access to Tesla's diagnostic and programming software, which they wrote for a total of 2,400 cars. With BMW, that software gets out into the wild, but I doubt we'll see it outside of Tesla's shop anytime soon. I'm curious how Chillout got that screenshot.

    With that screenshot, however, you might be able to convince Tesla to do the programming for you, since you know exactly what you want. I'd expect to pay an hour's labor.
     

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