How to modify signal from Speedometer?

Discussion in 'General Electronics Chat' started by jeremywrags, Nov 30, 2012.

Thread Status:
Not open for further replies.
  1. jeremywrags

    Thread Starter New Member

    Nov 30, 2012
    2
    0
    Hi All,

    I am thinking of a DIY project for my Jeep that will modify the speedometer signal before it hits the Jeeps computer as to correct the speed for the offset of bigger tires and alterd gearing.

    There is a commercial product HealTech SpeedoHealer but it's a little expensive and since I know enough to be dangerous about the Arduino I figured why not play with a solution myself...

    So here is what I know.

    1. There is a Sensor on my transfer case that has 3 Wires coming out of it.
    a. Red = 5v constant
    b. Black = Ground
    c. White = ? I am assuming that this is the singal that represents speed
    2. Inside the sensor is a gear that I could change if I didnt want to do this project

    I assume that the transfer case spins the gear and the sensor generates some sort of signal based on the number of teeth that the gear has.

    OK... I am a programmer but have very limited electronics knowledge. Can someone explain to me what the characteristics of that signal would probably be and perhaps how I might change it using an arduino?
     
  2. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
  3. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    tshuck is right. The moderators/administrators on this forum have chosen not to allow automotive modifications due to the possibility of mistakes that can lead to injury, or possible legal issues. Due to this decision, don't be offended if this thread gets closed.

    Regards,
    Matt
     
  4. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    You should be able to take your jeep to the dealer and have them correct the speed scaling in the computer, for a small fee.
     
    DerStrom8 likes this.
  5. jeremywrags

    Thread Starter New Member

    Nov 30, 2012
    2
    0
    Fair enough on the safety issue, thanks for the heads up. As for going to the dealer of course I could but what would be the fun in that. The whole point of this is to learn a little and solve a comon problem myself.

    Rather than asking for help in modifying the signal could I ask someone to explain what the signal characteristics would look like for monitoring. I am thinking it would just be a square wave with a frequency that represented the rate at which the gear turned? Does that sound right and if so could I use the Arduino to do an analogRead to measure the frequency?
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    Being totally uninformed, that is the first thing I would expect as well
    Being partially uninformed, I would say probably not. I believe the arduino measures on time vs. off time for the analogread function. I do not believe it measures frequency.
     
  7. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    Well, if it is, indeed, an encoder output, analogRead() is the wrong way to go...it is a digital signal... you'd need to relate encoder frequency to wheel velocity... it's a proportion...
     
  8. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    I am closing this thread as it violates AAC policy and/or safety issues.

    Quote:
    6. Restricted topics. The following topics are regularly raised however are considered “off-topic” at all times and will results in Your thread being closed without question:

    • Any kind of over-unity devices and systems
    • Automotive modifications
    • Devices designed to electrocute or shock another person
    • LEDs to mains
    • Phone jammers
    • Rail guns and high-energy projectile devices
    • Transformer-less power supplies
    This comes from our Tos:
    Terms of Service
    There will be enough sites where automotive questions can be discussed :
    Member selected automotive forums

    Bertus
     
Loading...
Thread Status:
Not open for further replies.