Digital speedometer

Discussion in 'The Projects Forum' started by yashowardhan, Feb 12, 2010.

  1. yashowardhan

    Thread Starter New Member

    Feb 12, 2010
    Ours is a group of 13 members, & we are building a small scale formula vehicle.The engine of the vehicle is 600 cc with carburetor, hence does not have ECU. The max expected speed is 120 kmph. So is it possible to design a digital speedometer that doesn't need ECU ?
  2. russ_hensel

    Distinguished Member

    Jan 11, 2009
    Yes. Any car from the 1950's.
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Let me correct that, any car from 1900 to ~1985.

    How about a modified bicycle speedometer/odometer?
  4. whatsthatsmell

    Active Member

    Oct 9, 2009
    Those aren't digital but will work if the transmission or transaxle has a place to insert the cable.

    Google digital speedometer and you will come up with a lot of solutions including gauge clusters and homemade circuits. After you look at the circuit and figure your cost to buy all the parts and put them together, the commercially available products look pretty good!
  5. Jack_K

    Senior Member

    May 13, 2009
    You can glue a magnet to the axle and mount a sensor on a fixed mount so it's close to the magnet as it spins.

    Measure the circumference of the tire on that axle and calculate how many pulses (revs) per mile you get. Use a counter IC to count the pulses from the sensor and display on an LCD display. You might have to finagle the counts to get true MPH.

    Search Digikey and some of the surplus sites for goodies.

  6. Art

    AAC Fanatic!

    Sep 10, 2007
    In modern cars you shopuld be able to get the signal from the sender in your gearbox.
    You can find the signal in the ECU or Body Electronics Module, and maybe trip computer too.
    I know you said you don't have an ECU though.
    I actually have a complete project digital speedometer for the pic16F84 (very cheap).
    (this one is not my own design) It measures up to 255Kmph.