Circuit for counting ignition pulses with inductive pickup using LM2907

Discussion in 'General Electronics Chat' started by Ahoo, Sep 28, 2014.

  1. Ahoo

    Thread Starter Member

    Sep 28, 2014
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    Hope you all will be fine.
    Can you please help me in making circuit for counting ignition pulses with the help of inductive pickup. I want to use LM2907 to do it. but what I know is that the signal from inductive pickup may be having a lot of noise. Another issue is that the signal might not be crossing zero.

    Any help in this regard please...please....please.................................................
     
  2. DNA Robotics

    Member

    Jun 13, 2014
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  3. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Where are the ignition pulses coming from and what are you going to do with the count?
     
  4. Ahoo

    Thread Starter Member

    Sep 28, 2014
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    thank you so much dear djsfantasi for your reply..
    the ignition pulses are basically coming from inductive pickup tied on ignition cables (when current is passed through conductor, a magnetic field is produced, this changing field will produce current/voltage in the inductive pick up that is tied on the cable)....... and i am counting them for measuring engine rpm
     
  5. Ahoo

    Thread Starter Member

    Sep 28, 2014
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    I already have gone through such kinds of manual... but being a beginner I am not that good to understand them good.... That is why I am posting here...Can you please shed some light on the circuit that can be used for this purpose
     
  6. Ahoo

    Thread Starter Member

    Sep 28, 2014
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    thank you so much dear djsfantasi for your reply..
    the ignition pulses are basically coming from inductive pickup tied on ignition cables (when current is passed through conductor, a magnetic field is produced, this changing field will produce current/voltage in the inductive pick up that is tied on the cable)....... and i am counting them for measuring engine rpm
     
  7. eetech00

    Active Member

    Jun 8, 2013
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    Hi

    Inductive pickup part number?
    2 cycle or 4 cycle engine?
    Max RPM?
    Supply voltage?
    What is output connecting to? A tachometer? If so, Tach part number?

    eT
     
  8. Ahoo

    Thread Starter Member

    Sep 28, 2014
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    Till now I didnt decide which inductive part number but am thinking of wrapping a few times copper wire arround ignition cable,,, This signal needs to be cleaned then.
    4 cycle
    Max RPM 4000
    Supply voltage .... I have no idea
    I am trying to connect output to arduino ADC channel but first I want to covert frequency to voltage with LM2907
     
  9. crutschow

    Expert

    Mar 14, 2008
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    If you want the frequency why not just square-up the pulses with a comparator and then count the digital pulses with the Arduino? Converting the pulses to voltage seems an unnecessary step.
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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  11. eetech00

    Active Member

    Jun 8, 2013
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    Hmm...

    Seems one could use a A1203 Hall sensor to detect spark (just tape it on the wire), have that feed a LM2917-8, that in turn provides input to the Adruino.
    Why an LM2917? Because some sort of signal conditioning (buffer and/or comparator) is needed anyway, it might as well be an 8 pin LM2917.

    eT
     
  12. Ahoo

    Thread Starter Member

    Sep 28, 2014
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    hey eetech00 can u send me draw me a full circuit and send me please... the reason I am using LM2907 is that I am not good in programming arduino.... but atleat if I know the rpm and voltage relation then it is easy for me to define equation
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Can't you use a capture function to interrupt a timer in Arduino as you would in a Picmicro?
    Seems to me a lot easier if it has the function.
    Max.
     
  14. Ahoo

    Thread Starter Member

    Sep 28, 2014
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  15. MaxHeadRoom

    Expert

    Jul 18, 2013
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    To obtain accurate pulses on a ICE, the ignition leads would be a last resort for me, the ringing and spurious spikes that may occur do not make for an accurate reading, I would look at other sources of engine rpm, which all you need is rpm and number of cyclinders in order to calculate, unless you need the precise point of each cyclinder firing?.
    Any gear teeth or other rotating object could be the source of pulses, or dependant on what type of ignition it has contact points etc, on modern motors, the ignition sensor is taken off the flywheel by prox sensor.
    Max.
     
  16. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Check this out, you could use one of these amp sensors (I've already used them in previous projects, and they work wondefuly) and connect it to a comparator to get what you want. Noise could be an issue, although the voltage spikes from the ignition would be so high that it would be comparatively small.
    http://amploc.fatcow.com/store/index.html
     
  17. Ahoo

    Thread Starter Member

    Sep 28, 2014
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    Thank you so much
    Can you please draw me the full circuit please..... I am really bad in these things...I am actually a mechanical engineer but have a little know how of these things... I just need it in my project.... Ur help will be really appreciated
     
  18. eetech00

    Active Member

    Jun 8, 2013
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    How many cylinders?
     
  19. Ahoo

    Thread Starter Member

    Sep 28, 2014
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    4 cylinders
     
  20. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Later engines often fire on every TDC rather than every other.
    Max.
     
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