i am currently working on a project which is located at this website
http://www.electronics-lab.com/proje...007/index.html

i am encountering a few problems with this circuit

i am not sure how it is supposed work

one of the transducers is giving off a noise signaling that it is transmiting but im not sure how to tell if the other transducer is receiving

i am also wondering what i should put at point 7 and 8
should i put a relay there?


if you see any errors in the schematic please point them out

also if anyone has built a working prototype of this ciruit please say so

I would greatly appreciate it

 

Hi Crazyman,
C1 shorts the received signal on the schematic but the pcb has it correctly grounded.

It looks like the circuit was designed to use a very old opamp for IC1 that needed C3. Now it uses a 741 opamp that does not need C3.

Use a switch between points 7 and 8 to latch the output when it is turned on. When it is turned off then the beeper or relay at the output will activate for each movement the circuit detects.

I don't think it will be sensitive and I don't think it will detect somebody wearing a sweater or a coat. Unless they move in front of a close wall.

__________________
Uncle $crooge

 

will it detect my hand if i move it in front of the transducers

 

I don't know if your hand reflects much ultrasound. It will block a reflection from a wall behind it.
I don't think the project is sensitive.

Inexpensive PIR motion detectors that people have for their driveways and alarms pick you up 15m away. They use infrared, not ultrasound.

__________________
Uncle $crooge

 

My ultrasonic rangefinder "sees" my hand just fine out to about 1-1.5 meters, but detects harder and flatter objects better at a distance. It can see a wall up to just under 3 meters away, and appears to be limited mostly by the timeouts I set in the code.

I don't know about your circuit; mine is just a simple 8051 uC using opposing output pins to drive a piezo transducer plus an op-amp receiver to detect the bounces.


Torben