High-speed audio sampling

[ajcoyote]

Hello,

I am a newb here, and I must say I love Arduino! I am a scientist who studies bats and I am trying to build by own "bat detector" which is a device that can record audio frequencies up to 125 kHz (250 ksps). From my research this is not possible with an Arduino, but it does seem possible with other devices, possibly a DE0-Nano, chipKIT Uno32 or NETDUINO. The key is I need to sample and save this data, either streaming onto a laptop or large SD cards. If I could figure this out it would be pretty awesome, as the devices for doing this run between $650 and $1500. But, since I'm a newb I need some help. Does anyone have a suggestion for which microcontroller or FPGA is best suited for this application? Also, is it possible to precisely set the sampling rate when pushing the ADC to such high rates on these devices? Any comments would be much appreciated!

[EasternStarGeek]

Have you considered down-converting the ultrasonic signal made by the bats you are trying to detect?

The way this is done is to mix your incoming audio with a local oscillator running at some nominal fixed frequency. Choose the frequency to lie somewhere midway between the lowest and highest frequency you are trying to detect. The product of the incoming audio with your local oscillator will result in sum and difference frequencies. By low-pass filtering of the mixer output, you should be able to recover the difference between the local oscillator and the incoming audio, which will be much lower in frequency than the orginal signal, thereby placing fewer demands on your chosen processor.

Look up "heterodyning" for more information about this technique.

This is the same technique that is used by ultrasonic "sniffers." Such devices down-convert ultrasonic signals into the audible range so that they can be heard in headphones. A tunable local oscillator can be used to measure the nominal incoming frequency by tuning until a "null" is heard (or more precisely, not heard)

This principle is used in many radio receivers (superhet design) as well as metal detectors. It can be accomplished with analog circuitry.

Good luck!

[rj44319]

Make sure reference is good ...like a oven crystal

[thefatmoop]

there must be a computer card that could do this for a reasonable price. Some of the dsPICS have very high ADC sampling rates.

10-bit 1 Msps Analog-to-Digital Converter
http://www.microchip.com/wwwproducts/De ... e=en010337

If you're new to micros then ignore that...pics aren't very friendly