I just finished the O'scope analysis of the Ultra sonic motion detector
this afternoon.
Here's what I discovered;
The Ultrasonic frequency is 50kHz with a 50% duty cycle.
Each query consists of 17 of these pulses (350 uSec) followed by a
listen
phase.
Depending on the number of queries demanded, 10 per sec, 25/sec, or
Paul's
120/sec, the pulse will have from 100 mSec (10 Hz) to 8.33 mSec to
receive the echo.
This means at 120 Hz, the maximum distance the pulse can travel and
still
get back before the next pulse is 1.4 m.
Of course, the pulse may arrive during the second listen time and that
throws the whole thing off. How is it determined that the detected echo
is from the most recent ping and not some past pulse? Sounds like
another lab day to me.....
pete
--
Pete Lohstreter "Reality is merely an
illusion,
The Hockaday School albeit a very persistent
one."
Dallas, TX 75229 A.
Einstein
petel@tenet.edu
plohstreter@mail.hockaday.org http://www.hockaday.org