Ultrasonic Transmitter questions

---
If your receiver is getting swamped because of too much power from
your transmitter, then you'll have to learn how to AGC the RX. Or,
alternatively, couple a transmitter to the receiver and a receiver
to the transmitter so that if the receiver gets overwhelmed it will
tell the transmitter to stop shouting. But make sure that the
receiver doesn't also shout, or else neither one of them will be
able to understand the other.

 

Some ultrasonic transducers have voltage maximums. You might want to find
out if the one you are using has a maximum, and arrange to limit the
voltage below that maximum.

Also, are you connecting the high side to 5V when output is 'off'? Is this
the same supply that you are using to power the logic chips? I haven't
spent much time looking at the circuit, but it is possible that there
could be some issues with noisy supply lines when the inductor is switched
to that rail.

--
Regards,
Bob Monsen

"Remind me to write a popular article on the compulsive reading of
news. The theme will be that most neuroses and some psychoses can be
traced to the unnecessary and unhealthy habit of daily wallowing in
the troubles and sins of five billion strangers. The title is 'Gossip
Unlimited' no, make that 'Gossip Gone Wild.'"
~ Jubal Harshaw

 

Hello,

Quite awile ago I started a project to make an as powerful I can get
ultrasonic remote control with TX and RX circuits capable of sending
and receiving serial data. I've been at it off and on and so far I
have it working as far as the TX circuit sending a single byte with a
qualifier byte over and over until the receiver circuit detects it and
acts upon it.

The latest TX circuit involves an upgrade of PIC from the 16F84A to
the 16F628A, change of code, elimination of a 40kHz 555 timer circuit
and transducer drive transistor with the addition of a relay, R/C
filter, AND gate, mosfet and an inductor.

As a rank newbe I hope you could spend a little time to take a look at
a partial schematic of the TX circuit and let me know what I've done
wrong or how I could improve upon it.
http://www.geocities.com/talionis.geo/Temp/temp.html

The main 13.8VDC power supply is 16V "zenered" and well filtered while
the 5VDC is regulated. The relay is because I have no automatic gain
on the RX circuit (don't know how) and it gets swamped if the TX is
too close.

Cheers,

Andrew.

 

Sorry for the late thankyou for your replies.

Cheers,

Andrew.