I was was looking to use one of the Arduinos to create a sin wave. I couldn't find a concrete source for what the output frequency ranges were, does anyone know?
It rather all depends on how you expect to output a sine wave on a device which doesn't normally have a DAC.
If you can say what range of frequency you are looking for then maybe we can tell you how best to get that with an Arduino. Your choices would include an external DAC and filtering or PWM and better filtering.
I wanted to output a sine wave which will then be amplified to be sent in pulses and used to create a signal to make my own sonar system. I didn't know that Arduinos didn't have a DAC. I was hoping to have one arduino with an output of of 10-20kHz, and one with an output of 1MHz. I don't know if either or both of those are possible.
This reference claims less than 1% distortion from 0 to 3 KHz with an upper limit of 16 KHz. Lacking a DAC, this is for sine wave PWM (pulse width modulation) which is a digital signal pretending to be an analog signal. To extract the analog signal the pwm signal must be filtered of high frequencies.
The Arduino Due has a DAC so it puts out a much cleaner sine wave.
Get yourself some dirt-cheap DDS devices off eBay and hook them to an Arduino. DC to multi-MHz, typically with a few tens of mHz resolution
Wildviewvermont: I wanted to output a sine wave which will then be amplified to be sent in pulses and used to create a signal to make my own sonar system. I didn't know that Arduinos didn't have a DAC. I was hoping to have one arduino with an output of of 10-20kHz, and one with an output of 1MHz. I don't know if either or both of those are possible.
You can buy ultrasonic rangefinder modules for under $2. In what way is your sonar different? Why do you need 1 MHz for sonar?
I would expect that the quality of the sin wave burst to the transducer is not that critical, however, the bigger issue is going to be on the receive side. Typically decent sonar systems have some sort of gated receiver with variable gain that increases over time for the more distant reflections. I personally have not been impressed with digital type sonar (depth sounder) type devices since sound reflects off all sorts of things including changes in temperature/salinity in the water or even in air, it gets reflections off hot air from the furnace vents etc. and then it takes the first reflection as the correct distance. I much prefer some sort of visual display that lets me see all the reflections and look for the pattern showing the various structures it is seeing. Your actual use will determine if that is an issue or not for your application.
simple oscillators will give you the frequencies required to good accuracy.
For the receiver a wide range log detector would be useful. AD make some good one.