Author Topic: Recognizeing a frequency  (Read 3785 times)

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Offline 555 timer chip guyTopic starter

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Recognizeing a frequency
« on: March 20, 2007, 05:40:01 PM »
Dos any one have a circuit that can recognize a specific frequency.

Offline Kohanbash

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Re: Recognizeing a frequency
« Reply #1 on: March 20, 2007, 07:44:42 PM »
do a google search for a notch filter or bandpass filter.
you can use an op amp or a simple RLC circuit.
« Last Edit: March 20, 2007, 07:48:03 PM by sdk32285 »
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Offline robot321

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Re: Recognizeing a frequency
« Reply #2 on: March 20, 2007, 07:48:49 PM »
the G8870 decodes DTMF Freqs.

Offline 555 timer chip guyTopic starter

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Re: Recognizeing a frequency
« Reply #3 on: March 21, 2007, 01:37:41 PM »
It needs to be able to recognize square wave forms.

Offline Kohanbash

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Re: Recognizeing a frequency
« Reply #4 on: March 21, 2007, 08:15:44 PM »
maybe a DAC before the notch filter. Or use a cap in parallel with the receiver to convert to sinusoidal. I don't know of any offhand but they make tone decoder IC's which also might work
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Offline trigger

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Re: Recognizeing a frequency
« Reply #5 on: March 21, 2007, 08:42:40 PM »
why don't you ADC your signal, and then filter in software? (e.g., use DSP).  Much easier to find a square wave. 
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Offline 555 timer chip guyTopic starter

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Re: Recognizeing a frequency
« Reply #6 on: March 22, 2007, 02:06:12 PM »
thanks but I don't know how to do that yet. :(

Offline Kohanbash

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Re: Recognizeing a frequency
« Reply #7 on: March 22, 2007, 03:01:30 PM »
You will need to play with the values a lot but here is a basic circuit that should work.
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Offline 555 timer chip guyTopic starter

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Re: Recognizeing a frequency
« Reply #8 on: March 24, 2007, 09:13:50 AM »
You will need to play with the values a lot but here is a basic circuit that should work.
Thanks for that schematic I was looking at some thing very similar a littel wile ago
do you haze any basic starting values I could use for maybe 100Hz , and also I heard you could use a comparator and a crystal to recognize a frequency.

Offline ed1380

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Re: Recognizeing a frequency
« Reply #9 on: March 24, 2007, 09:18:53 AM »
<-noob
Isn't that what an osciliascope is for?
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Offline zamboniman60

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Re: Recognizeing a frequency
« Reply #10 on: March 25, 2007, 06:26:28 PM »
well, if you don't have an extra $160 laying around for an oscillosope, you could use the "inductor in series with an LED brightness test" or the "speaker and function generator guesstimation".

 


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