Hey there folks,
I'm currently in the middle of a larg-ish project of 3D position location using ultrasonics and the principle of trilateration.
My transmitter has 4 ultrasonic transducers on it, and it sends a 40kHz burst for 0.1ms and then goes silent for 0.9ms. It uses Max232 chips to step up the voltage level to the transducers so that the range is further. This works fine.
I made some recievers each with a ultrasonic transducer, then an amplification stage with a single-rail op-amp and then a 567 tone decoder. These were all working before christmas, however, on my return to the lab all but one of them has stopped working.
What is supposed to happen, is that when the pulse is generated from the transmitter, the reciever then 'catches' it, this 40kHz is then amplified, then the tone decoder goes low (OV), (and when there is no 40kHz tone, it goes high (5V) ).
However, the tone decoder always seems to activate now, even without the transmitter switched on. I am using 0.1uF and 0.01uF decoupling capacitors and a regulated power supply, and obviously they were all working at some stage so I'm now wondering what went wrong. Could it be the power supply?
These are pretty much the circuit diagrams i'm using, except obviously the transmitter has max232s.http://www.eetasia.com/ARTICLES/2002MAR/2002MAR08_RFD_DA_AN.PDF
Cheers for taking a look