waveform type detector

Thread Starter

the_insomniac

Joined Dec 26, 2006
1
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.
WAVEFORM TYPE DETECTOR
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.
 

Distort10n

Joined Dec 25, 2006
429
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.

....or...
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?
 

Thread Starter

the_insomniac

Joined Dec 26, 2006
1
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...
 
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