Voltage to Sound Help

Of course. You insert tab 'A' into slot 'B' and push the blue button.

HTH

Bob

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).

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.

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

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

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

NE602 crosses to a NTE7164

However, I cannot cross your NE612

Par, I haven't looked into the parts you mention. Basically what you want is a "Four-quadrant multiplier". There are a lot of ways to implement this; traditionally it was done with a diode bridge where you weren't worried about perfect results, such as when the output was going to be filtered anyway. Note that you get both sum and difference components, and at audio frequencies they are hard to separate with filters alone.

Best regards,

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

Poking around, it looks like those will work at any frequency. This is also a "legacy" part, but without the built-in oscillator:

Here are digikey's part numbers for dip and SOIC: MC1496POS-ND MC1496DR2OSCT-ND

For the oscillator, use something with a sine-wave output. For something cheap and simple, google for phase shift oscillator.

The ones i have seen the specifications on go from DC up to as high 100's of MHz. Just a minority go past 1 MHz. If you use "analog multiplier" in a search engine you should get many part numbers and specification sheets. Bandwidth trades off in cost and accuracy.