waveform type detector

Discussion in 'The Projects Forum' started by the_insomniac, Dec 26, 2006.

  1. the_insomniac

    Thread Starter New Member

    Dec 26, 2006
    Hi.I have a project,i haven't an idea yet,firstly i want to receive your ideas and then design my circuit.If you have an idea about this,please share with me so i can evaluate these and make my circuit more accurate.Project is as following.
    The circuit will detect the given input waveform.The input waveform will be a triangular,sine or square wave,with a frequency of having 1000-3000 Hz and having an AC amplitude of 2V to 4V and a DC offset of -5 to 5 volts.In this circuit project,using an multimeter,voltmeter,oscilloscopes or any instrument which measures voltage or current is not allowed.But,red and green LEDs can be used as indicators.
  2. beenthere

    Retired Moderator

    Apr 20, 2004

    Do some googling on phase-locked loops. That's what they're for.
  3. Distort10n

    Active Member

    Dec 25, 2006
    I don't know how easy that would be. Clock IC's are typically digital and have a reference clock looking for those nice sharp edges of a square wave. I do not think they will be keen on triangle and sine wave inputs.

    You may have to build your own PLL. Shouldn't be too difficult by itself since a PLL is a classical feedback system.

    From your description you need to determine the waveform type regardless of frequency and amplitude. As an example...You need a circuit that can differentiate between a 1Vpp,1 kHz square wave and a 2Vpp, 1.25 kHz triangle wave. Seems tough once you add in the changing DC bias.

    Some immediate thoughts come to mind is using a DC clamp circuit (DC restorer) and perhaps look into the different RMS values of a sine, triangle, and square wave to your advantage.

    Is there not a difference in the spectral components of various (ideal) waveforms? Man, I wish I paid better attention in class. If so, why not use a uC for a cheap and quick FFT?
  4. the_insomniac

    Thread Starter New Member

    Dec 26, 2006
    I can only use capacitors,inductors,and op-amps because we only learned that devices.I am just at 2nd year and I just introduced to circuits design...