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PICList Thread
'ultrasonic ranging'
1997\07\12@234537 by Frank B. Scalzo

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I am working on a project that needs to find the distance to objects.
Currently I am using using a PIC16C84 as my controller. I'm using 40kHz
transmit and recieve transducers from polaroid. I am driving the
transmit transducers by attatching one of it's leads to RA1 and the
other to RA2. In my code RA1 is always the opposite of RA2 and I switch
them at 40kz 20 times, to make an outgoing train of pulses. My reciever
transducer has one pin to ground and one to a 2 transister amp
(2n2222's). I am having problems with range, I fear recier amp is not
strong enough, but if I increase it's gain, I detect ghost (false)
signal returns. Any suggestions to improve my design? I want a range of
2-15 feet accurate within only a foot. Also,does anyone know of a way to
narrow by field of detection. My current design detect objects off to
the side.

1997\07\13@003110 by Glen Benson

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At 11:32 AM 7/12/96 -0400, you wrote:
>I am working on a project that needs to find the distance to objects.
>Currently I am using using a PIC16C84 as my controller. I'm using 40kHz
>transmit and recieve transducers from polaroid.  Any suggestions to
improve >my design? I want a range of
>2-15 feet accurate within only a foot. Also,does anyone know of a way to
>narrow by field of detection. My current design detect objects off to
>the side.


This site has much on ultrasonic ranging using the pic16c84.
http://www.mindspring.com/~sholmes/robotics/ultrasw.htm

Glen Benson

1997\07\13@020538 by Terry

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At 11:32 AM 7/12/96 -0400, you wrote:
>I am working on a project that needs to find the distance to
objects.
>Currently I am using using a PIC16C84 as my controller. I'm using
40kHz
>transmit and recieve transducers from polaroid. I am driving the
>transmit transducers by attatching one of it's leads to RA1 and the
>other to RA2. In my code RA1 is always the opposite of RA2 and I
switch
>them at 40kz 20 times, to make an outgoing train of pulses. My
reciever
>transducer has one pin to ground and one to a 2 transister amp
>(2n2222's). I am having problems with range, I fear recier amp is
not
>strong enough, but if I increase it's gain, I detect ghost (false)
>signal returns. Any suggestions to improve my design? I want a range
of
>2-15 feet accurate within only a foot. Also,does anyone know of a
way to
>narrow by field of detection. My current design detect objects off
to
>the side.


There was an article on a PID pong device in a Circuit Cellar Ink
from about a year ago that detailed using the polaroid transducer to
sense distance.  The author could possibly give you a dirth of
information as he addressed ghost images very briefly.

Sorry I can't be more help.
Terry Ewing
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1997\07\13@022629 by Mal Goris

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Frank B. Scalzo writes:
> I am working on a project that needs to find the distance to objects.
> Currently I am using using a PIC16C84 as my controller. I'm using 40kHz
> transmit and recieve transducers from polaroid.
[snip]
> I detect ghost (false) signal returns. Any suggestions to improve my
> design?

This topic was discussed in some detail recently, with talk of schemes
for improving detection of the return pulse. Have a look at the
piclist archive which Andrew Warren just today gave the URL of and
which is

       http://www.428main.com/piclist/

Mal Goris
--
http://www.nfra.nl/~mgoris/

1997\07\13@084134 by Tom Mariner
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Are you working with the indoor or the ruggedized Polaroid transducer? The
indoor (the round black mesh-looking one) has a lot better gain, but doesn't
like being splashed alot. The outdoor is elipsoid-shaped and has a more
focused pattern.

In any case, you have to be careful of:

The ringing of the input signal after sending the sonar pulse (You must blank
for x amount of time.)
targets that will bounce back an even stronger signal. (sometimes)
signals from other transducers firing in the same frequency.
broadband sonar noise -- Try shooting white noise ala air brakes or an air
hose nearby and watch a real strong echo.
Both frequency and voltage on the output transducer are critical with rather
narrow bands.

I've got a patent in that field and had so solve a lot of stupid little
problems to get the devices to work reliably. (PIC C57 which also powered the
RS-485 network.) You can get more accurate than a foot -- Ours is running .6
inches reliably. I'd like to get more detailed with code, etc. but I'll bet
our customer would get reasonably upset.

Tom

----------
From:   pic microcontroller discussion list on behalf of Frank B. Scalzo
Sent:   Friday, July 12, 1996 11:32 AM
To:     spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU
Subject:        ultrasonic ranging

I am working on a project that needs to find the distance to objects.
Currently I am using using a PIC16C84 as my controller. I'm using 40kHz
transmit and recieve transducers from polaroid. I am driving the
transmit transducers by attatching one of it's leads to RA1 and the
other to RA2. In my code RA1 is always the opposite of RA2 and I switch
them at 40kz 20 times, to make an outgoing train of pulses. My reciever
transducer has one pin to ground and one to a 2 transister amp
(2n2222's). I am having problems with range, I fear recier amp is not
strong enough, but if I increase it's gain, I detect ghost (false)
signal returns. Any suggestions to improve my design? I want a range of
2-15 feet accurate within only a foot. Also,does anyone know of a way to
narrow by field of detection. My current design detect objects off to
the side.

1997\07\14@014602 by Andy Tucker

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part 0 2274 bytes
----------
From:   Tom Mariner[SMTP:.....Tom_MarinerKILLspamspam@spam@MSN.COM]
Sent:   Sunday, July 13, 1997 8:41 AM
To:     PICLISTspamKILLspamMITVMA.MIT.EDU
Subject:        Re: ultrasonic ranging

Are you working with the indoor or the ruggedized Polaroid transducer? The
indoor (the round black mesh-looking one) has a lot better gain, but doesn't
like being splashed alot. The outdoor is elipsoid-shaped and has a more
focused pattern.

In any case, you have to be careful of:

The ringing of the input signal after sending the sonar pulse (You must blank
for x amount of time.)
targets that will bounce back an even stronger signal. (sometimes)
signals from other transducers firing in the same frequency.
broadband sonar noise -- Try shooting white noise ala air brakes or an air
hose nearby and watch a real strong echo.
Both frequency and voltage on the output transducer are critical with rather
narrow bands.

I've got a patent in that field and had so solve a lot of stupid little
problems to get the devices to work reliably. (PIC C57 which also powered the
RS-485 network.) You can get more accurate than a foot -- Ours is running .6
inches reliably. I'd like to get more detailed with code, etc. but I'll bet
our customer would get reasonably upset.

Tom

----------
From:   pic microcontroller discussion list on behalf of Frank B. Scalzo
Sent:   Friday, July 12, 1996 11:32 AM
To:     .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
Subject:        ultrasonic ranging

I am working on a project that needs to find the distance to objects.
Currently I am using using a PIC16C84 as my controller. I'm using 40kHz
transmit and recieve transducers from polaroid. I am driving the
transmit transducers by attatching one of it's leads to RA1 and the
other to RA2. In my code RA1 is always the opposite of RA2 and I switch
them at 40kz 20 times, to make an outgoing train of pulses. My reciever
transducer has one pin to ground and one to a 2 transister amp
(2n2222's). I am having problems with range, I fear recier amp is not
strong enough, but if I increase it's gain, I detect ghost (false)
signal returns. Any suggestions to improve my design? I want a range of
2-15 feet accurate within only a foot. Also,does anyone know of a way to
narrow by field of detection. My current design detect objects off to
the side.



1997\07\14@143943 by Tom Mariner

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On Monday, July 14, 1997 12:32 AM, pic microcontroller discussion list  On
Behalf Of Andy Tucker wrote:
{Quote hidden}

blank
> for x amount of time.)
> targets that will bounce back an even stronger signal. (sometimes)
> signals from other transducers firing in the same frequency.
> broadband sonar noise -- Try shooting white noise ala air brakes or an air
> hose nearby and watch a real strong echo.
> Both frequency and voltage on the output transducer are critical with rather
> narrow bands.
>
> I've got a patent in that field and had so solve a lot of stupid little
> problems to get the devices to work reliably. (PIC C57 which also powered
the
{Quote hidden}

Yes, both Polaroid and Murata Erie have ruggedized units. The Polaroid is a
single unit and the Murata device has separate send and receive transducers.
In both cases you will have to whack them with a lot more power to get the
range you want, but they have much better water / shock / temperature specs.
Also, the units we used a few years ago had a much narrower resonant frequency
band than the indoor types. We also experienced some unit to unit frequency
drifts.

Tom

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