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PICList Thread
'ultrasonic ranger problem'
1999\01\18@140708 by Brian Duran

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I have a problem...(I don't think it is pic related)

My ranger consists of 4 basic parts; timing, pic controller, transmitter
and recieving.  I seem to have a good ouotput pulse from my transmitter,
which is generated by the pic.  However my return pulse isn't so good.
Regardless of distance the "pulse" travels you see a return "wave" which
is half the frequency of the "pulse" and accures before the next pulse is
to be sent. How soon it accures varies(it isn't connected to when you see
the pulse you are accurally looking for, since this can accure both in and
out of the way front.).  The wave is equal in amplitude to the pulse.

       Here is what I have done:
               Placed a bead on the transimitting transducer wires.  When
you disconnected the receiving transducer, you see no noise.
               Place a metal shield between the two transducers.
               Place foam for vibration between the two transducers.
               Tested many rangers.
               Covered transmitter and receiver, still noise.
               Moved them.
               Switched them.
               Turned power on and off(interesting that then wave takes
longer to reform then the pulse)

If you ahve any sujestions or tests I should try, all help is appriciated.
Brian

1999\01\19@230325 by Sean Breheny

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Hi Brian,

I have worked on several ultrasonic ranger prototypes, and this was one o
the most common problems.


First, I would try disconnecting the transmitting transducer and see if
the noise disappears. If it doesn't, you know that it is not being
received thru the air.

Second, I would try building an identical receiver, but without the PIC (
just the transducer and amplifier) on a totally separate board and
separate power supply from the rest of the circuit. See if you see any
such noise when it is close to the transmitter versus when it is far away.

What design are you using for the ranger?

Good luck,

Sean


On Mon, 18 Jan 1999, Brian Duran wrote:

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