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Traffic Light Sensors?

Discussion in 'Roadster' started by finout, Mar 1, 2011.

  1. finout

    finout Member

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    I've only been driving my new Roadster 2.5 for a month. But 3 times now (twice at one intersection and once at another), I've noticed that the traffic light sensor has failed to detect the Tesla. I'm not imagining it: I've driven through these intersections dozens to hundreds of times over 8 years in my ICE cars and had never seen the light patterns "ignore" my car before. All 3 times, my Roadster was the only car in the sensor area.

    It doesn't happen everywhere.

    I observed once, a couple years ago, a lone motorcycle that also failed to trigger the sensor and sat through a light cycle at one of these intersections.

    Has anyone else seen this? Any theories? Small size, not enough metal, no ignition coil?
     
  2. scott451

    scott451 KWH-PWR#1349Sprt,S Sig#96

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    Palo Alto
    I've seen this too. There is one light near my house that seem to not recognize my Tesla. It happens when I am the first car. But it doesn't happen every time.
     
  3. Sparrow

    Sparrow S105/ Roadster 189

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    I've seen this happen occassionally in my lighter non-metal EVs. In my Sparrow, when I am first in line, I tend to move a little further forward when I see a regular car come behind me so that if I haven't triggered the sensor the next car has. Of course it doesn't work if there aren't any other cars behind me. Haven't seen it happen in my Roadster yet.
     
  4. mpt

    mpt Electrics are back

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    Same here; the solution, in the US, turn right on red then do a u-turn and pray that the light doesn't change in the meantime!

    I've also tried backing up slowly to see if there's a point where the battery and motor are enough to trigger the sensor!

    I wonder how the law applies to you siting for five mins with no cars coming then edging out?
     
  5. Dragon

    Dragon Lightning Green Fairytale

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    Oh my god! 200m from my home is such a sensor light. And right next to it is the police station. Well, lets see how it works out...
     
  6. mpt

    mpt Electrics are back

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    lmao!
     
  7. tennis_trs

    tennis_trs 2010 2.0 Roadster Sport

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    I haven't had any traffic light issues yet in my 18 months and 20,000 miles, so hopefully there aren't too many anti-EV traffic lights.
     
  8. Doug_G

    Doug_G Lead Moderator

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    I've never had this happen with my Roadster, and the vast majority of intersections here have the sensors. Maybe it depends on what vendor produced the sensors?

    In Ottawa they often paint three yellow dots along one side of the loop, so that motorcycles know where to stop. If you have the dots, then stop so your battery pack is right on top of them.

    If you don't have dots, then look at the pavement; you can usually see the loop because they cut the pavement, insert the loop, and then reseal it with tar.
     
  9. Lloyd

    Lloyd Active Member

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    #9 Lloyd, Mar 2, 2011
    Last edited: Mar 2, 2011
    There is a solution to not triggering traffic lights in the roadster if anyone has a continuous problem with this. There is a product that is used with motorcycles to trigger the light. It has one side prepared with adhesive and measures about 1" x 2". Just apply it to the bottom of the car somewhere, no wiring, no maintenance. It is cheap $22.99 and can be purchased at amazon.com.

    http://www.amazon.com/High-Power-Motorcycle-Green-Trigger/dp/B0038B4BW6
     
  10. Jaff

    Jaff Active Member

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    I'd rather have a button that just changes my stoplight from red to green on demand...:wink::biggrin::biggrin:
     
  11. Doug_G

    Doug_G Lead Moderator

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    Interesting. I imagine it's simply a ferrite or similar high permeability material. Seems to me you'd need a pretty big chunk to be detected.

    Okay I found a web site explaining it... How to Trigger Green Traffic Lights - wikiHow As expected, they talk about "magnets" -- you actually need a magnetic material with a very high permeability, not necessarily a magnet.

    Here's an alternative idea: Make a large shorted coil of wire. The loop could be quite large, e.g. wrap it around the diameter of the trunk or something similar. It would probably work a lot better and cost almost nothing.
     
  12. strider

    strider Active Member

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    #12 strider, Mar 2, 2011
    Last edited: Mar 2, 2011
    I assumed this would be a problem but have not had a problem yet in 4 months and 3k miles. That being said, having ridden motorcycles for years, California designs their light sensors for motorcycles which I think makes the difference.

    The loops look like this:

    /---\
    |///|
    |///|
    \---/

    /---\
    | | |
    | | |
    | | |
    | | |
    \---/

    They make a smaller loop with more sensing wires in it at the front of the line in case a motorcycle is by itself.
     
  13. SByer

    SByer '08 #383

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    In fact, in California at least, if a sensor doesn't trip for a motorcycle or bicycle, it's considered misadjusted, and you can complain to the city. Where it gets put on a list. But with enough cyclists in the area around here, I've never had a problem in the Roadster (and I know where the bad spots are for my cycle).

    Note that it may help to be offset to one side or the other so the wheels are directly over one edge of the loop - for the front most loops, that is generally tuned to be the most sensitive part (so cyclists can trip it).
     
  14. NigelM

    NigelM Recovering Member

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    The coils in the road are activated when the magnetic field is disturbed by a mass of metal or a powerful magnet. As a motorcycle rider in Florida, this is a pretty common problem, but this magnet does the trick and it's been attached to the bottom of my bike with double-sided tape for 3 years now.

    Red Light Changer
     
  15. dpeilow

    dpeilow Moderator

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    Neodymium - don't tell the EV-haters or they will start going on about Chinese mines...
     

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