Voltage to Sound Help

A simple peak detector can be used to convert the RX output to a psuedo-DC value that is proportional to distance (amplitude detector). This voltage can be used to drive a VCO or voltage-to-frequency converter if you'd like to have the pitch change vs. distance. If you really want volume vs. distance, then you'd have to have an oscillator of some kind (to make the tone), followed by an audio amp whose gain can be controlled via the aforementioned detected amplitude (via a FET in linear region, or something like that).

Hi All

I have created an Ultrasonic TX and RX. Now I would like to convert the

output to an audible sound.

When an object gets closer I would like the tone get stronger and stronger.

Can someone pls tell me how I could do this. I checked the output of the RX

and it's Voltage increases as someone comes close by.

Thx

SQ

Gain R2/R3+1 28V |\\ | .-o| \\ |/ input---|>|---o-----o--' | | --o---| | | .-| / | |>

| | | |/ [R2] | [R1] --- | | | | --- '--------o | | | | ===== | | [R3] ===== | | | | gnd ----------o-----o------------o-----'

The diode and cap keep track of the peak, and the resistor allows it to fade over time.

The amplifier (the triangle) then amplifies the input by some amount so that it varies from 0 to 28V. The NPN transistor follows the input, and uses it to set the input voltage of a variable output piezobuzzer, like one of the amseco PAL328 series, which will get louder as the voltage across it increases. Mouser has them.

The amp can be any single-supply opamp that can handle 30V from Vcc to Vee (perhaps an LM324?). A standard non-inverting feedback is probably the best. Determine your maximum input voltage, minus a diode drop (use a shottky diode for smaller drop) and set the gain so the output is 28V at that voltage.

Besides the advice others have given, there is another totally different approach: Use a mixer (multiplier) to multiply the received signal by a local oscillator whose frequency is (say) a few hundred Hz from the TX. The output product contains components at sum and difference frequencies, proportional to the original amplitudes.

That way you not only hear the amplitude, but you can hear doppler frequency shifts as well.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

mix it with a carrier 1000Hz below (or above) the frequency that drives the ultrasonic transmitter. then rectify it and run it through a low pass filter

I've always been interested by the idea of using a mixer to play with the sum of two frequencies but have never tried.

Can you provide some advice as to what to use? A quick search reveals parts like the NE602 and NE612 as possibly useful components (though I couldn't locate either at digikey) but I'm wondering if these aren't too "high frequency" for uses in the Hz or KHz range.

Any advice?

TIA