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olmasters
Joined: 11 Mar 2007
Posts: 1
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 11 Mar 2007 0:43 Ultrasonic mic --> Voltage, Ultrasonic mic --> Voltage |
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Hi, At the moment I am making a reverse parking sensor system,
basically its very simple. An astable circuit provides a 40,000Hz signal from an ultrasonic transmitter, this signal is then reflected from an object and recieved by an ultrasonic reciever.
However, I was wondering if anyone knew of a circuit diagram, that would enable an output from the ultrasonic mic, to be converted to a voltage (it currently ony emmits capacitance), which would vary, depending on the signal strength recieved by the mic??
Your thaughts would be much apriciated
Ollie 
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Beowolf
Joined: 19 Jun 2006
Posts: 135
Helped: 7
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| 12 Mar 2007 12:52 Re: Ultrasonic mic --> Voltage, Ultrasonic mic --> Vol |
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check this out
http://www.analog.com/en/subCat/0,2879,760%255F1077%255F0%255F%255F0%255F,00.html
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rogerynt
Joined: 06 Mar 2007
Posts: 109
Helped: 11
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| 12 Mar 2007 13:44 Re: Ultrasonic mic --> Voltage, Ultrasonic mic --> Vol |
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Check the followings :
1.) Bias the mic properly. ( You can think in a way that it is similar to an audio mic except for picking up signal at much higher frequency ) When the mic receives a signal there is a voltage change at the node.
2.) Use a filter amp. to amplify this induce signal. The amp itself should have a hystersis loop to get rid of small changes. The purpose is to filter away small changes to reduce the probability of false detection ( similar to schmit trigger )
3.) Set window comparators for trigger level.
Let say put the mic 2 feet away from wall and then set the trigger level. Then repeat this process to obtain different trigger level according to your specifiied distance.
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