Please help me with the number (km/h)

    #1

    Hi.
    I'm working on an electronic display to measure the speed (km/h) on my Opel Corsa A, '89, 4 speed gearbox.
    I'm trying to eliminate the mecanical cable that connects the gearbox and the speed gauge.
    Everything is ready, but i don't know the formula witch will help me find the speed i'm going.


    So. can anyone tell me the number of times the cable spins in 1Km? If i know that, everything is done. Where can i find this number?


    I know it's not a Kadett, it's Corsa, so please excuse me if my question is out of place.
    I don't speak german, i'm from romania.
    Thank you.

    #2

    Hi..


    you know that there is a dedicated sensor which screws onto
    the gearbox and gives you an electrical signal.. ?! This could
    be evaluated a bit easier i guess, but I don't know your setup
    exactly.. so tell us more. Counting the rpm of the mechanical
    cable, as you call it, seems a much harder approach.


    The circuitry needed to evaluate the actual speed is another
    thing. You don't want to install the original opel kadett gsi
    digital speedo, but a completly self-made display ?!..


    ..
    Rob.

    Suche (stand 12/2014):
    +++ Kadett-E Caravan Himmel
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    Einmal editiert, zuletzt von tbone ()

    #3

    it will be completly made from scratch, and also integrating digital tacho, water temperature, oil pressure etc.
    I know that there is a dedicated sensor, but i've also made it from scratch. Where i live, it's hard to find that kind of parts, and if i do, the price is very high.
    So, my sensor screws into the gearbox, and gives me 2 electric signals (+5V and then 0V) on every rotation. I've made it using an hall sensor and 2 magnets (bolted on the axel).
    The mechanical cable will be completley gone.
    And i have to know how many rotations of the "ex-cable" takes for 1km.
    For example, on Dacia (the most usual car in Romania, we build it), 1 rotation of that cable = 1 meter. That means 1000 rotation/kilometer.


    That's the number i'm looking for. To evaluate the speed using electric signals received from my sensor.


    I'm using ATMEL microcontrollers and led displays.

    #4

    Since I'm not really too familiar with electronics and stuff,
    the only advice i could give, would be to concider the
    "hands-on-method" again.. o)
    Which means.. push the car and simply count the rotations..
    I assume noone here knows the rotations per meter, you have
    to find out for yourself, just as you did for the Dacia.


    Btw, I know Dacia, my father once drove an orange
    colored, the model I don't remember, but in east
    germany, it was one of the better cars to drive, but my
    dad had to sell it as he was short on money.. o)
    By that time I was 5 or 6 years old.. nice to think of.. o)


    Nevertheless, your project sounds very interesting,
    I wouldn't mind you to post a few pictures when finished
    or while still in progress.. o)


    Btw, you could change the subject of this thread into:
    "Wieviele Umdrehungen macht die Tachowelle pro km ?"
    This should raise peoples attention..

    Suche (stand 12/2014):
    +++ Kadett-E Caravan Himmel
    +++ Kadett-E Caravan Frisco/Club-Spezial Schürzen (v+h)
    +++ TSW Imola 15" - 17" mit LK 4x100

    Einmal editiert, zuletzt von tbone ()

    #5

    why that difficult?


    you surely just want to know which speed sensor you need.


    i built a lcd display in my `94 corsa b with 45 ps. i used the 8 IMP sensor of the kadett e. that works fine. on the lcd display of the kadett e you have a switch that you can chose the 8IMP or 16 IMP setting. try both setting to check with value comes closer to the reality. remember to turn of and on the ignition after the setting.


    PS: falls es nich schon gesagt wurde er meint die "wegstreckendrehzahl" die immer aufm tacho unten steht.

    Einmal editiert, zuletzt von kadett2005 ()

    #6

    No! Er hat sich selbst einen "Sensor" gebaut, mittels
    Hallgeber, der auch nur einen Impuls pro Umdrehung
    liefert, und er möchte nun wissen wieviele Umdrehungen
    das Teil pro km macht, also wie oft dreht sich die
    "Tachowelle" bei DistanzX..


    Er will keinen 0815-Digi anschliessen, weil er eigene
    Instrumente baut und die Schaltung dazu ebenso..

    Suche (stand 12/2014):
    +++ Kadett-E Caravan Himmel
    +++ Kadett-E Caravan Frisco/Club-Spezial Schürzen (v+h)
    +++ TSW Imola 15" - 17" mit LK 4x100

    #7

    Hi cosminache123,


    if I understood you right, you made a selfmade electronic for the speedometer, situated in the place where the original speedometre cable is plugged in the gearbox.


    So what you need ist the "Wegstreckenzahl", which can be read directly on the instrument cluster of the original speedometer.
    There you find written e.g. K=1125. This means the speedometer cable takes 1125 revolutions per kilometer.
    But keep in mind , if you changed the gearbox or the tire-dimension also the "Wegstreckenzahl" will not be the same anymore.
    So an information what gearbox (F10, F16 or so) and original and future tire dimension, would help to solve your problem.


    Greatings to Romania


    andy67

    Ich fahre seit 25 Jahren Kadett D, da weiß man was man hat!

    #8

    Die Wegstreckenzahl gibt in der Tat die Umdrehungen
    der Tachowelle pro km an ?!.. So einfach ?!.. o)

    Suche (stand 12/2014):
    +++ Kadett-E Caravan Himmel
    +++ Kadett-E Caravan Frisco/Club-Spezial Schürzen (v+h)
    +++ TSW Imola 15" - 17" mit LK 4x100

    #9


    So ist es !!
    Da heute nur noch elektronische Tachometer gebaut werden, ist so etwas nicht mehr geläufig. Ich arbeite aber in einem Unternehmen, dass seit den 20er Jahren Tachometer herstellt (die mit den drei Buchstaben). ;)

    Ich fahre seit 25 Jahren Kadett D, da weiß man was man hat!

    #10

    andy67
    Alles klar, die Wegstreckenzahl war mir ein Begriff, dass sich
    diese nun doch so leicht erklären lässt, wusste ich nicht,
    dachte da wären ganz monopolistische Formeln dahinter.. o)


    @cosminache123
    Sorry if I did confuse you in any way. But now you have the
    answer to your question.. isn't that cool.. ?! o)
    Would be nice if you keep us informed on how you succeed.

    Suche (stand 12/2014):
    +++ Kadett-E Caravan Himmel
    +++ Kadett-E Caravan Frisco/Club-Spezial Schürzen (v+h)
    +++ TSW Imola 15" - 17" mit LK 4x100

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