Tachometer for diesel engines 2

Discussion in 'OnBoard Electronics & Controls' started by caslor, Jul 13, 2012.

  1. caslor
    Joined: Jul 2012
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    Location: Athens - Greece

    caslor New Member

    [​IMG]

    Hi to all friends Here
    I am a new member and i found this old post and need some help about the schematic :(

    * The z6v & Z9v are zener diodes ??
    * any instrument can work? lets say a 15amp vdc ? Because i went to the electronic shop and couldnt hepl me with the schematic... tell me what kind of instrument would be better


    Thanks in Advance

    Ps : the original thread was to old so couldnt post a reply.. so i open a new one.. sorry
     
    1 person likes this.
  2. gonzo
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    gonzo Senior Member

    The 555 is a timer chip. However, it doesn't indicate what kind of display it will run.
     
  3. Tim B
    Joined: Jan 2003
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    Tim B Senior Member

    Have a look at this site:

    http://www.555-timer-circuits.com/

    In your circuit it is set up as a monostable, triggered with each pulse from the engine. This drives a moving-coil meter hard over, presumably using the return-spring and the pulse-rate to give higher readings for higher RPM.

    To be honest this is a poor way to do it. You would be better to use a schmit triggier to clean up the incoming signal, and a PIC to measure the pulse-width. Output an NMEA 0183 signal (or NMEA2000), And then display it on a commercial gauge.

    Cheers,

    Tim B.
     
  4. pistnbroke
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    pistnbroke I try

    Keep it simple tim ..the circuit will work fine ..yes they are zenners and you need a 1MA moving coil meter movement ..if you are lucky you may get a 270 deg movement from an old rev counter ..or why not just get the whole thing from say a land rover dash ..diesel model ....

    The W output is half wave rectified AC the frequency of the pulses varies with the rpm.
     
  5. Tim B
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    Tim B Senior Member

    Pist,

    Simplicity to me means the minimum number of moving parts.

    Sorry,

    Tim B.
     
  6. pistnbroke
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    pistnbroke I try

    Its only got a needle in a moving coil meter ...????
     
  7. Tim B
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    Tim B Senior Member

    Make it solid-state, and it has no moving parts.

    Tim B.
     
  8. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Caslor, this circuit works fine if you use a moving coil meter from which you remove the shunt resistor. Buy one for 5 VDC or 5 Amps so you don't have to make a new scale.
     
  9. pistnbroke
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    pistnbroke I try

    If the guy wants an analogue display he needs a moving coil meter......KISS
     
  10. caslor
    Joined: Jul 2012
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    Location: Athens - Greece

    caslor New Member

    Hi Again to all of friends that had the time to answer to my question...
    Sorry for the delate but i was all the weekend to my boat .. sailing race

    Thanks for the info about zener and the coil meter... :)

    i will start building it :)

    i want to inspect my engine as it didnt have a tacho rpm meter and dont know if i get the maxim power of it

    Again thanks all of you and special the ''CDK'' for the original post of this electronic schematic ;)
     
  11. pistnbroke
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    pistnbroke I try

  12. caslor
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    caslor New Member

  13. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    I think you dont fully understand..the variable resistor is for you to adjust the reading so it reads right. you need to measure the engine speed with another method and adjust your meter to show the right reading.

    The reading depends on ..the number of poles on the alternator and the pulley ratio so you need engine at say 4000rpm and adjust variable resistor so it reads 4 on your scale.......ok
     
  14. caslor
    Joined: Jul 2012
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    caslor New Member

    yes i know that...

    My puley is 1:1 ratio with the engine puley so that is easy...

    i have download the program that cdk suggested in his older post.. and if cant determine the right rpm from there... i will use a mobile rpm meter that one friend has.. and will adjust the var resistor


    one question... .1uf is 1uf? this ''.'' confused the guy in the electronics shop :p
     

  15. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    pulley ratio is 2:1 for a petrol and 3:1 for a Diesel so you need to check ...does not matter you need to know what the engine rpm is to calibrate your home made tacho ......my advice if you want to learn build one ...if you want to get the job done buy one ....

    The capacitors are 0.1 uf not 1.0 uf
     
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