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  • Vehicle speed converter

    Hi..

    i want to design a vehicle speed converter for car which takes speed signal from ECU of car and convert it to digital format. i don't have car. i don't know what kind of speed signal come out from the ECU of car. I am an Electrical and Electronic engineer. i have experience developing electronic circuit. I want to know the voltage VS speed waveform diagram of the ECU speed out put. Can anybody help me?

  • #2
    Any idea what car or ECU model you are designing for? This would probably help people answer your question.
    Originally posted by ghettocruzer
    I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
    Want to:
    -Find out about the new iBug iPad install?
    -Find out about carPC's in just 5 minutes? View the Car PC 101 video

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    • #3
      Dear Bugbyte,

      Thank you for your reply.

      Proton, Isuzu cars. is different car use different technologies? I have no idea ECU models.

      Thanks again

      kirupa

      Comment


      • #4
        Frequency to voltage is easy enough (LM2907/LM2917), and many speed transducers are pulse types - eg Nissans use a 10 pole sensor on the box (20 pulses per cable rev?) and they can be fitted to (older) Isuzus.

        Isuzu often use a reed switch mounted in the speedo (I'm not kidding - and it lasts for hundreds of thousands of miles/km!).


        As to digital....

        Comment


        • #5
          Dear OldSpar,

          Thank you for your reply.

          I didn't get answer for my question. i want to know what kind of speed signal come out from the ECU of car?

          1) is this pulse? ( different speed has different frequency)
          2) is this linear voltage? ( different speed has different voltage)


          Thanks

          Comment


          • #6
            Hmmmmmmmmmmm....we don't have Protons stateside. Perhaps you can get a pic of one so we can figure out the corresponding model and go from there?

            Comment


            • #7
              Originally posted by kirupa View Post
              I didn't get answer for my question. i want to know what kind of speed signal come out from the ECU of car?
              Which ECU?


              Normally they don't come out of the ECU unless there is a need - and that could be as anything (eg, analog proportional; though usually pulse, coded (binary etc), or discrete/command level (threshholds).

              Comment


              • #8
                Hi..

                Thank you for your reply.

                Say, now vehicle is moving 20Km/h. i am connecting a oscilloscope to ECU speed output? How will the oscilloscope waveform be? Now i am changing speed to 40Km/h. Now how will the oscilloscope waveform be ?

                Comment


                • #9
                  It is VERY unlikely that you will be able to design this without having access to the car. Why are you developing this for a car you neither own nor have access to? Is this a commercial project?
                  Originally posted by ghettocruzer
                  I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
                  Want to:
                  -Find out about the new iBug iPad install?
                  -Find out about carPC's in just 5 minutes? View the Car PC 101 video

                  Comment


                  • #10
                    Ditto. Again which ECU?

                    Or answer this:
                    How will:
                    - an analog voltage
                    - a bitsream (hex or binary or BCD)
                    - PWM or...
                    - variable frequency pulses
                    look on your CRO?

                    Are you using DC or AC input?

                    Answer the above (at least 4 answers; 8 if AC/DC variation; extra if hex is different to binary)
                    ... and I'll continue.


                    Also, which Isuzu ECU puts out a speed signal?

                    Comment


                    • #11
                      this is getting interesting.... I'm following along. What are the odds this goes nowhere?

                      Comment


                      • #12
                        What do you mean goes nowhere? It never got anywhere! (LOL!)

                        I would have thought an Electrical and Electronic Engineer could have envisaged the many signals that exist and that it is simply a matter of determining which it is and interfacing appropriately. (Then again, after seeing 3rd year Electrical & Electronic Engineering students that couldn't connect a DMM, or text-book authors that still thought electricity had a "direction" (ie, EITHER positive ions/holes OR electrons!) and thought of Maxwell's Equation(s) as something fantastic, I'm not surprised.)


                        Maybe kirupa wants to design a universal interface? But in that case, I have already provided the info kirupa requires (for most systems).


                        Maybe when kirupa provides appropriate info, we can progress.
                        (Maybe kirupa will find his ECUs do NOT provide speed information. After all, why would they?


                        I don't mind going nowhere - that's like many dreams.
                        It's going in circles, costing a fortune, trial&erroring that which is already known... (Especially since finding the true & correct info is so easy.... LOL - that's a joke - no chance of that these days! Progress? - yes, if you understand for what.)

                        Comment


                        • #13
                          Tap into an ABS tone ring, that should give you a PWM output that increases in frequency as the vehicle's speed increases. Tap all 4 and you can also check if the car is in a skid.

                          If it doesn't have one of those, you'll need to tap into the sensor in the transmission, or, if it were a truck, the center diff. Those are probably also PWM, but an oscilloscope will tell you for certain.

                          Comment


                          • #14
                            So is it a tone, or PWM, or a frequency thing?


                            Answer: Frequency.

                            If any have pwm or tone, let me know.


                            But this thread was a dead end, or rather - a dead start. The OP simply had no idea...

                            Comment


                            • #15
                              ABS tone ring will be frequency modulated, yes. Although the pulses will be longer as the vehicle slows, they will still be the same percentage duration.

                              And it's the PART that's called a tone ring, it's just part of the name of the part, has nothing to do with the signal.

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