Ultrasound with PIC12F629

[T.Jackson]

And, Melanie’s right. You're only generating ultrasound for 20mS, 1,000 cycles of 20uS, 1 / 20mS = 50Hz. And the more I think about it with what I just wrote, if you were out of bounds with bandwidth you wouldn't hear anything at all. Completely attenuated.

Best Regards,

Trent Jackson

[T.Jackson]

Keep in mind that you're applying close to 5V to the input of the LM386.
IO ports on PIC’s are CMOS with a guaranteed minimum of 73% of VCC when set high. (You'll lose a bit because of the coupling cap) With this in mind, assuming a supply rail for the LM386 at around 9V, you really don't want a gain of much more than about 1.5 Of course, I am assuming that you don't have a volume control set in place enforcing a limitation on volume.

Best Regards,

Trent Jackson