Is this a stepper motor? How do i work it? From speedometer

Discussion in 'The Projects Forum' started by cduluk, Dec 21, 2009.

  1. cduluk

    Thread Starter Member

    Aug 2, 2009
    14
    0
    Hey guys. I accidentally put this in the general forum and moved this here.

    I am working on a gauge cluster modification in my car and need some help.

    Some car gauge clusters do this neat trick where the gauge needles rotate all the way in one direction, and all the way back in a few seconds- upon start-up.

    See this vid of the Lexus IS cluster: Watch the speedo and tach needles
    http://www.youtube.com/watch?v=ZAKacaoNN04

    I want to make my car's gauge needles do the same thing.
    I thought i could run a relay that would break the factory circuits to the needle motors upon startup for maybe 3 seconds. And during these 3 seconds, i can maybe use a motor driver to send the right signals to the motors so that the needles swing right and left just like the needles from the cluster in the Lexus IS. Then after the 3 seconds, the relay connects the factory circuit so the cluster performs normally.

    My only problem is that i don't know how the gauge cluster motors work. I am assuming they're stepper motors (but i could be totally wrong).

    I bought a used cluster from a Lexus Rx330 (which use the same motors as my 2008 Lexus Rx400h cluster) so i can test out the motors before i do it to my actual cluster.

    Here is the cluster taken apart. I’m focusing on the speedometer needle motor.

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  2. cduluk

    Thread Starter Member

    Aug 2, 2009
    14
    0
  3. cduluk

    Thread Starter Member

    Aug 2, 2009
    14
    0
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    Now, on the back of the speedometer needle motor is a 14 digit number. But the tach, fuel and temp motors all have a different 14 digit number.
    The speedo number is: BO 41123.214157.3
    The tach number is: BO 41123.214214.1
    The fuel number is: BO 41123.214142.5
    The temp number is: BO 41123.214126.7


    Not sure if these numbers mean anything?
    Can anyone give me some information as to how I should go about doing this modification? Upon start-up, i want the speedometer needle to:


    1. Start at 0mph (where it would be anyways)
    2. Be rotated 225 degrees clockwise from the 0mph spot
    3. Be rotated 225 degrees counter-closkwise back to the 0mph spot

    ...in about a second or so (same time it takes for the IS needles to rotate and return).

    I want to figure out how to do the speedometer needle first, then i'll worry about the other needles...


    Thanks for any help!
     
  4. JMD

    Member

    Dec 9, 2009
    96
    0
    What you could do, is figure out what type of input the speedometer get, and make a circuit that provides a 1-shot-input, from minimum to maximum.
     
  5. sudharma99

    New Member

    Apr 6, 2009
    1
    0
    The mysterious metal sliver is a spring plate. The pointers going fullscale and returning is most probably a power up self test. Will be a complicate job to duplicate it on another system.
     
  6. JMD

    Member

    Dec 9, 2009
    96
    0
    Not if you know what type of signal it gets on the input. You can then replicate that, and make it go from minimum to maximum and back to minimum. If you make that as a one-shot, it will only fire upon turning on the car - as wanted.
     
    Last edited: Dec 22, 2009
  7. Duane P Wetick

    Active Member

    Apr 23, 2009
    408
    19
    Its all software programming...easy to do too...the hardware has nothing to do with it. You just have to gain access to the software program.

    Cheers, DPW [ Everyone's knowledge is in-complete...Albert Einstein]
     
    Last edited: Dec 22, 2009
  8. cduluk

    Thread Starter Member

    Aug 2, 2009
    14
    0
    Hmm, i'm not sure i'd be able to change any of the car's computer programming, i wouldn't even know where to begin :(

    Can someone tell me what type of motor this is? In my reading i'm seeing all these different names, "bipolar" "unipolar" etc... Can someone explain to me how this motor works? What types of signals does it use to move the needle? Is it a resistance thing?

    There are 4 leads to the motor.

    What i can try is to install the cluster in the car, and remove the motor and use a multimeter to determine what's going in the pins at 0mph, 30mph, 60mph etc... But i don't know what to hook up where...

    Example, am i looking for voltage to pins 1 and 2? Resistance between pins 3 and 4? Would the average multimeter (digital) be enough to do a test? What would i need to hook up where, and what settings do i set the meter to? What am i looking for as mph changes? Which of the 4 pins do i hook up?

    I'm a total newbie on this stuff, but as soon as i understand how everything works, i should be good :)

    If i know how the motor works, maybe that can help me understand this more?

    Could i find the speed sensor, find what signals it's putting out at various mph's, and estimate what the signal would be at 210mph? Then upon startup, run a relay to make the computer think the speed sensors telling it i'm going 210mph? Would that make the needle SHOOT to the 210mph mark? Then, i could release the relay which would set everything back to normal, and would the needle SHOOT back to 0mph? Would this give me the swing pattern i'm after?

    Also, would tampering with the speed sensor mess up anything else with the car? Would the fact that the speed sensor's telling the computer i'm going 210mph while starting up in PARK affect or break anything? It's a hybrid car, so i want to be careful...

    All i want to do is get the motor to think i'm traveling 210mph for a second (so the needle quickly spins to that point) then a second later, make the motor think i'm at 0mph (so it quickly spins back). Obviously messing with the speed sensor signal would work, but is there another way that doesn't let the whole CAR think i'm going that fast?

    Thanks for any more info guys!
     
    Last edited: Dec 24, 2009
  9. JMD

    Member

    Dec 9, 2009
    96
    0
  10. cduluk

    Thread Starter Member

    Aug 2, 2009
    14
    0
    but what are the details on the speedometer motor?
     
  11. whitehedr

    New Member

    Apr 9, 2009
    1
    0
    My guess this is a 12v stepper motor. Look at the Gecko drives page. I like this particular product as it should do what you want. http://www.geckodrive.com/product.aspx?c=3&i=14471

    You would need to experiment of course with the motor in the extra cluster. I would suggest a relay to isolate the motor contacts and then a 555 timer circuit to drive the motor via the step pulse and with with logic to control the motor direction.

    This is not a particular inexpensive solution but it should be workable.

    RWW
     
  12. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    The speed sensor for the car simply sends a pulse train to the cars central computer or engine control module. That module uses the frequency of the pulse train to perform various functions such as: 1) move the needle on the speedometer to the proper position, ;2) compare the speed of the drive shaft (what is usually sensed by the speed sensor) to the engine RPM to detect slippage within the transimission,. The engine control module will use the internal programming to move the speedometer needle to the proper position by sending pulses to the coils in a particular quadrature pattern to move the needle. Knowing the quadrature direction and number of pulses, the needle can be moved upscale or downscale to any position. If you ever wanted to change tire size (a common thing on pickup trucks) a trip to your dealer can load a correction factor into the control module to restore speedometer accuracy. It is all magic in the box.
     
  13. cduluk

    Thread Starter Member

    Aug 2, 2009
    14
    0
    What if i switched polarity on the motor?

    Meaning i set up a relay so that during the first second upon startup, it opens the factory circuit, and a closes a new circuit so that the pins are reversed. So the e- that was going to pin 1 would go to pin 4, and the e- going to pin 2 would go to pin 3.

    Just reversing the polarity...

    Would the needle now shoot to the right side of the gauge (at ~155mph), making the vertical line through the pin of the motor an axis of symmetry?

    Then after a second, the relay would switch back to the factory circuit, making the needle return to 0.

    Would this work with this motor?
     
  14. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    Best option for you at this point would be to go to a salvage yard and buy a unit similar to the one you want to modify. Experiment to your heart's content knowing that if you blow it up, you will still have a working unit in your car.
     
  15. bluebrakes

    Active Member

    Oct 17, 2009
    245
    7
    you can often control the instrument panel through the diagnostic port. Get a PIC to send the right data down the diagnostic port and you'll do just that.

    Is it OBD2?
     
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