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Data acquisition using microphone jack

Discussion in 'General Electronics Discussion' started by THUNDERBOLT, Jul 28, 2011.

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    Aug 29, 2010
    I have absolutely no experience using DAQ software or writing code, yet I am keen to gather some data from a motorcycle, (without first having to learn any of the above).

    One of the inputs from the motorcycle is its RPM which is about11000 maximum, lets say 12000 to provide some headroom, and to make the calculations simple.

    12000 RPM = 200Hz

    Considering most audio editing software, such as COOLEDIT96, are used to working with 44100Hz, it doesn't seem a very difficult task to record 200Hz

    So my question is, if I take for example my inductive pickup sensor, which hangs around my sparkplug lead, then feed the sensors output pulse into my microphone socket on my minidisc recorder, (after controlling the pickups output voltage level of course), should I have a reasonable recording or will it just be a mess?

    What I am aiming to do is to record engine speed, and also the input from a sensor measuring wheel speed. The whole purpose is to have tool which will let me determine that the two are syncronised. If the two signals don't syncronise it proves there is clutch slipping present.

    That is the whole aim of the experiment, i.e. to diagnose a slipping clutch.

    This is a problem which continually raises its head for me.

    I ride motocross machines and at times on loose ground it can be difficult to differentiate between wheelspin and clutch slip. This simple audio recording would make it so easy to analyse, if it worked.

    It seems simple yet I'm not convinced that I'm not overlooking something fundamental.

    For the second recording channel, its my intention to position an inductive pickup close to the rear sprocket mounting screw heads. In a specific gear, while providing about 50mph-60mph roadspeed, there will be roughly 80 samples per second from the rear wheel, since there is 8 screw heads holding the sprocket on, and the wheel is turning around 10Hz.

    I'm sure someone has done something similar but I just can't find it on Google.

  2. Resqueline


    Jul 31, 2009
    Ignition pulses tend to look quite messy but with suitable filtering I guess it can be made to work.
    One other possible pickup point is the alternator. A pickup coil might get the magnet field directly from outside, or one could perhaps use the generated AC.
    On the rear wheel I'd try to get the pickup at the sprocket teeth instead of the mounting screws, to obtain a higher frequency which will be easier to record & process.


    Aug 29, 2010
    Thanks for that.

    My pickup is a FLUKE which has some filtering built in. It produces quite a nice clean pulse.

    Rearding the rear wheel, I realise the higher resolution is available, but I don't really think I need such high accuracy. It is so simple to pickup on the bolt heads, while sensing the teeth becomes a bit more involved. I suppose I can try the simple solution first and if it doesn't work, then consider your suggestion. Thanks again.
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