Ultrasonic range finding - components

[Danny T]

Hi all,

I want to build a simple ultrasonic range counter. I've got 400ST/400SR
transducers. I found a simple schematic here:

http://fly.srk.fer.hr/~nix/Projects/Sonar/Sonar_Shematic.gif

But I don't need the LCD. I just want to send 40Mhz pulses, wait a few
ms, then start listening for the start of the reply. Can anyone suggest
the components suitable for the amplifier shown here? As I understand
it, I can detect the range from the time taken between my pulsing, and
the echo, so all I need to do is drive a PIC input high. Somewhere else
I read that I need to amplify the signal by around 1000 times to do this?

Ta!

--
Danny

 

[Robert Monsen]

Danny T wrote:

Hi all,

I want to build a simple ultrasonic range counter. I've got 400ST/400SR
transducers. I found a simple schematic here:

http://fly.srk.fer.hr/~nix/Projects/Sonar/Sonar_Shematic.gif

But I don't need the LCD. I just want to send 40Mhz pulses, wait a few

This would be kHz, I guess.

ms, then start listening for the start of the reply. Can anyone suggest
the components suitable for the amplifier shown here? As I understand
it, I can detect the range from the time taken between my pulsing, and
the echo, so all I need to do is drive a PIC input high. Somewhere else
I read that I need to amplify the signal by around 1000 times to do this?

Ta!

That 'schematic' is useless.

Here is one schematic, but it doesn't look all that promising:

http://www.robot-electronics.co.uk/htm/srf1.shtml

Here is another one from EDN, who occasionally have useful stuff, but it
isn't pic-centric:

http://www.web-ee.com/Schematics/Ultrasonic%20Range%20Finder/Ultrasonic.htm

Here is one from TI:

http://www.web-ee.com/Schematics/Ultrasonic%20Range%20Finder%20II/slaa136a.pdf

If you search for 'ultrasonic ranger' or 'ultrasonic distance
measurement' you'll get several thousand hits.

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.

 

[Larry Brasfield]

"Danny T" <danny@nospam.oops> wrote in message news:41e6d593$0$41658$ed2619ec@ptn-nntp-reader03.plus.net...

Hi all,

I want to build a simple ultrasonic range counter. I've got 400ST/400SR transducers. I found a simple schematic here:

http://fly.srk.fer.hr/~nix/Projects/Sonar/Sonar_Shematic.gif

But I don't need the LCD. I just want to send 40Mhz pulses, wait a few ms, then start listening for the start of the reply. Can
anyone suggest the components suitable for the amplifier shown here? As I understand it, I can detect the range from the time
taken between my pulsing, and the echo, so all I need to do is drive a PIC input high. Somewhere else I read that I need to
amplify the signal by around 1000 times to do this?

There are several changes needed to make your range
finder work something like you probably hope.
1. The gain needs to be varied, from low to high, as echoes
(or their absence) from greater ranges are collected. This is
because signals become progressively weaker with range.
2. There should be some kind of frequency selection in your
receiver. Otherwise, its noise performance will be many
times worse than it needs to be.
3. You need some kind of detector, a circuit that converts
the 40 MHz received wavelets into baseband bumplets.

You may want to look at the AD8331 by Analog Devices.
It will handle the time varying gain if you are willing to provide
a ramped voltage to it. Its gain is appropriate for sonar, if
your detector can see a few hundred mV.

There are range-finding IC's available. By some measures,
those will be simpler than anything you can do with a lot of
separate parts.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[Danny T]

Robert Monsen wrote:

That 'schematic' is useless.

I thought so too, but it looked simple compared to others

http://www.robot-electronics.co.uk/htm/srf1.shtml
http://www.web-ee.com/Schematics/Ultrasonic%20Range%20Finder/Ultrasonic.htm
http://www.web-ee.com/Schematics/Ultrasonic%20Range%20Finder%20II/slaa136a.pdf

If you search for 'ultrasonic ranger' or 'ultrasonic distance
measurement' you'll get several thousand hits.

I know, I found lots, but many seem to be very complex, such as having
555 timers and tone decoders, which I believe I don't need. The timing
can be done by my chip, and as I understand it, the time delay in
receiving the response is enough to calculate the distance, so the
actual signal isn't important. I also believe my transducers are geared
for around the 40Khz range, so noise hopefully won't be a problem...?

--
Danny

 

[Danny T]

Larry Brasfield wrote:

There are several changes needed to make your range
finder work something like you probably hope.
1. The gain needs to be varied, from low to high, as echoes
(or their absence) from greater ranges are collected. This is
because signals become progressively weaker with range.

As I understand it, the signal isn't that important, just the time
delay. As long as I can get the start of the signal, I can use the
timing to calculate the distance, and ignore the waves of the signal?

2. There should be some kind of frequency selection in your
receiver. Otherwise, its noise performance will be many
times worse than it needs to be.

I was looking at the NE567 tone decoder, but I think the transducers are
heard for 40Khz anyway. Rapid seem to have the NE567 as "discontinued"
with no replacements - if you think it'd be beneficial, I'm sure I could
get some from somewhere.?

3. You need some kind of detector, a circuit that converts
the 40 MHz received wavelets into baseband bumplets.

As long as the first sign of a signal is enough to be picked up by my
PIC, is it that important?

There are range-finding IC's available. By some measures,
those will be simpler than anything you can do with a lot of
separate parts.

I understand that, but I'm doing it to gain knowledge, not the end
product, and this way looks like it'll teach me a lot!

--
Danny

 

[Larry Brasfield]

"Danny T" <danny@nospam.oops> wrote in message news:41e6e594$0$20979$ed2619ec@ptn-nntp-reader02.plus.net...

Robert Monsen wrote:
That 'schematic' is useless.

I thought so too, but it looked simple compared to others


http://www.robot-electronics.co.uk/htm/srf1.shtml
http://www.web-ee.com/Schematics/Ultrasonic%20Range%20Finder/Ultrasonic.htm
http://www.web-ee.com/Schematics/Ultrasonic%20Range%20Finder%20II/slaa136a.pdf If you search for 'ultrasonic ranger' or
'ultrasonic distance measurement' you'll get several thousand hits.

I know, I found lots, but many seem to be very complex, such as having 555 timers and tone decoders, which I believe I don't need.
The timing can be done by my chip, and as I understand it, the time delay in receiving the response is enough to calculate the
distance, so the actual signal isn't important. I also believe my transducers are geared for around the 40Khz range, so noise
hopefully won't be a problem...?

Unless your tranducers are quite efficient, the noise
that appears to exist at the amplifier input will not
be limited to the bandwidth of the tranducer.

Good luck with your 1-bit DSP software.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[Andrew Holme]

Danny T wrote:

Anthony Fremont wrote:
[snip]
Sounds easy enough. The 741 I understand just amplifies, but I don't
understand the 393. Does it just go high/low if one side is higher
than
the other?

Yes.

You really need to have an oscilloscope for playing with this
stuff.

I know, but they're not quite as cheap as a multimeter, so when I've
decided electronics is for me, I'll think about getting one

You can build kits, or follow someone else's _detailed_ plans; but you
need to be very experienced or very lucky to successfully design AC
circuits of this complexity without a 'scope.

Cheap 'scopes sell on e-Bay all the time. You don't know what you're
missing.

 

[Larry Brasfield]

"Danny T" <danny@nospam.oops> wrote in message news:41e6e6e4$0$14591$ed2619ec@ptn-nntp-reader01.plus.net...

Larry Brasfield wrote:

There are several changes needed to make your range
finder work something like you probably hope.
1. The gain needs to be varied, from low to high, as echoes
(or their absence) from greater ranges are collected. This is
because signals become progressively weaker with range.

As I understand it, the signal isn't that important, just the time delay. As long as I can get the start of the signal, I can use
the timing to calculate the distance, and ignore the waves of the signal?

There are a couple important principles in detection that
you overlook at the expense of performance. One is to
match the receiver sensitivity spectrum to the expected
signal spectrum. Another is to set the detection threshold
above the noise but not so far above as to miss events.
Without time-varying gain or threshold, you cannot effect
the latter. Without some frequency selectivity, you cannot
effect the former.

2. There should be some kind of frequency selection in your
receiver. Otherwise, its noise performance will be many
times worse than it needs to be.

I was looking at the NE567 tone decoder, but I think the transducers are heard for 40Khz anyway. Rapid seem to have the NE567 as
"discontinued" with no replacements - if you think it'd be beneficial, I'm sure I could get some from somewhere.?

Something as simple as an LC bandpass filter would be
just about as good. The NE567 might not lock onto the
returned echo fast enough to yield decent range resolution.

3. You need some kind of detector, a circuit that converts
the 40 MHz received wavelets into baseband bumplets.

As long as the first sign of a signal is enough to be picked up by my PIC, is it that important?

If you operate your device in an otherwise quiet environment,
and do not care about getting as much range as your preamp
and transducer would allow, then, no, it is not important. My
bet is that you will discover many acoustic noise sources that
you do not yet deem significant.

I hope you have an oscilloscope for this project. If so, you
may want to hook it up with some gain to your transducer
and see what is floating around where you plan to do sonar.

There are range-finding IC's available. By some measures,
those will be simpler than anything you can do with a lot of
separate parts.

I understand that, but I'm doing it to gain knowledge, not the end product, and this way looks like it'll teach me a lot!

Very likely, and more than you imagine just now.

I would ask, (rhetorically), what do you hope to learn? You
appear to already understand the most basic idea of sonar
range measurement. Do you hope to go beyond that? If so,
you would do well to at least understand how the above two
principles apply to the problem.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[Brian]

"Danny T" <danny@nospam.oops> wrote in message
news:41e6d593$0$41658$ed2619ec@ptn-nntp-reader03.plus.net...

Hi all,

I want to build a simple ultrasonic range counter. I've got 400ST/400SR
transducers. I found a simple schematic here:

http://fly.srk.fer.hr/~nix/Projects/Sonar/Sonar_Shematic.gif

But I don't need the LCD. I just want to send 40Mhz pulses, wait a few
ms, then start listening for the start of the reply. Can anyone suggest
the components suitable for the amplifier shown here? As I understand
it, I can detect the range from the time taken between my pulsing, and
the echo, so all I need to do is drive a PIC input high. Somewhere else
I read that I need to amplify the signal by around 1000 times to do
this?

Ta!

--
Danny

Recently I did a project for an ultrasonic ranging device. Since the
receiver is the more tricky part, I drew only the receiver for you (with a
few comments on it's design). It probably has a greater sensitivity than you
need, but you can reduce that). You can see it at
http://www.fncwired.com/UltrasonicExample/
Brian

 

[Danny T]

Brian wrote:

Recently I did a project for an ultrasonic ranging device. Since the
receiver is the more tricky part, I drew only the receiver for you (with a
few comments on it's design). It probably has a greater sensitivity than you
need, but you can reduce that). You can see it at
http://www.fncwired.com/UltrasonicExample/

That looks simple enough for even me - thanks Brian. I'll give it a go
when my breadboards aren't so full of other wires

--
Danny

 

Danny,

I think this PDF file may be exactly what you are after.
Google for
"application note an101" sonar sensor

or http://www.generexe.AN101.PDF

Cheers,

Andrew.


On Thu, 13 Jan 2005 20:09:56 +0000, Danny T <danny@nospam.oops> wrote:

Hi all,

I want to build a simple ultrasonic range counter. I've got 400ST/400SR
transducers. I found a simple schematic here:

http://fly.srk.fer.hr/~nix/Projects/Sonar/Sonar_Shematic.gif

But I don't need the LCD. I just want to send 40Mhz pulses, wait a few
ms, then start listening for the start of the reply. Can anyone suggest
the components suitable for the amplifier shown here? As I understand
it, I can detect the range from the time taken between my pulsing, and
the echo, so all I need to do is drive a PIC input high. Somewhere else
I read that I need to amplify the signal by around 1000 times to do this?

Ta!

--
Danny

 

[Lord Garth]

<Rubicon> wrote in message news:41eca212.1602787@news.netaccess.co.nz...

Danny,

I think this PDF file may be exactly what you are after.
Google for
"application note an101" sonar sensor

or http://www.generexe.AN101.PDF

Cheers,

Andrew.

That link is http://www.generexe.com/AN101.PDF

 

This isn't exactly an answer, but .... The following link points to a
one-piece ultrasonic send/receive unit that outputs a voltage:

http://www.halted.com/commerce/catalog/product.jsp?product_id=17559&czuid=1105979182765

.... the vendor had many left (on Jan 11) and the small sample I have
(one) works.

Wade Hassler

 

[Anthony Fremont]

"Lord Garth" <LGarth@Tantalus.net> wrote in message news:6IRGd.18855.

That link is http://www.generexe.com/AN101.PDF

Well looky there, they stole my design. ;-) I opted for the
differential input method on the op-amp though.

 

[Lord Garth]

"Anthony Fremont" <spam@anywhere.com> wrote in message
news:0NSGd.24031$Ta2.103@fe2.texas.rr.com...

"Lord Garth" <LGarth@Tantalus.net> wrote in message news:6IRGd.18855.

That link is http://www.generexe.com/AN101.PDF

Well looky there, they stole my design. ;-) I opted for the
differential input method on the op-amp though.

Post yours on alt.binaries.schematics.electronic ... The above link does not
have
the source code in the pdf with the schematic. In my opinion, it is
incomplete
without the code. A hex file would be nice too so that no compiler is
needed.

 

[Danny T]

Anthony Fremont wrote:

A scope is probably the best single instrument you can own for tinkering
with this stuff. You can pick them up really cheap on e-bay. You don't
need a 650Mhz tripple beam scope, but a dual trace with 20 - 50MHz
bandwidth would be nice for your robotics/electronice/microcontroller
tinkering. You can get them so cheap that you could sell it if you
decide you don't like electronics and not really lose any money.

"so cheap"?
The one you linked to sold for nearly $300!

--
Danny

 

[Danny T]

Rubicon wrote:

I think this PDF file may be exactly what you are after.
Google for
"application note an101" sonar sensor

or http://www.generexe.AN101.PDF

Excellent. I've printed it out, and when my clock isn't taking up my
breadboards, I'll have a fiddle. I've got a couple of op-amps n things
now, with some more stuff (hopefully!) arriving from Rapid tomorrow

--
Danny

 

[Danny T]

Larry Brasfield wrote:

There are range-finding IC's available. By some measures,
those will be simpler than anything you can do with a lot of
separate parts.

I understand that, but I'm doing it to gain knowledge, not the end product, and this way looks like it'll teach me a lot!

Very likely, and more than you imagine just now.

I would ask, (rhetorically), what do you hope to learn? You
appear to already understand the most basic idea of sonar
range measurement. Do you hope to go beyond that? If so,
you would do well to at least understand how the above two
principles apply to the problem.

I meant that I want to learn about electronics. Interfacing with
different parts, blowing stuff up, etc. Practice/experience is the best
way to learn. If everything works as I expect it to, great, but usually,
it doesn't, and obstacles means learning

--
Danny

 

[Danny T]

Anthony Fremont wrote:

I did this a little while back. It's more difficult than it first
appears, but not as bad as some people here would have you believe.
Usable results can be obtained without varying the gain on the receiver
amplifier or bandpass filtering the received signal, but it would be
better to have those things in an ideal world.

I understand, but I'd like to start simple. If I can build something
that's confused by handclaps, I'll post back here and find out why ;-)

If I'm given a complex schematic to build, I won't understand the
purpose of every component, but building simple and adding to it, I
reckon I'll learn more

My device worked well at 8' - 10' which was plenty good enough for robot
work. One interesting thing that I uncovered while working with these
devices was that the transducers are very narrow banded. They are
practically deaf at frequencies that stray very far from their center
frequency (usually around 40KHz, but can be much higher in industry
applications). This is like getting free bandpass filtering by the
device itself. Look up Q factor as it pertains to tuned circuits for
more information on this phenomena. They are not completely immune to
noise (such as hand clapping near the transducer), but with careful
processing of your data you can filter out the garbage. Normal ambient
noise in a house caused virtually no problems.

Sounds good. I'm not too bothered by noise for now - if I can get
something up and running, I've then got a "test" bed for plugging "noise
reduction" in.

I used a 741 op-amp as the first stage of amplification and then fed
that straight into one side of a 393 comparator to square up the pulses
and push them up to near 5V. The other input of the comparator had a
voltage divider that set the pins voltage just a few (10-15) millivolts
higher than the DC idling output of the 741. The output of the
comparator was fed to the RB0 interrupt pin on a PIC so that the
received pulses arrival could be timed accurately.

Sounds easy enough. The 741 I understand just amplifies, but I don't
understand the 393. Does it just go high/low if one side is higher than
the other?

I would send about 5 or 6 cycles of 40KHz signal out the sending
transducer (connected to two PIC pins for generating a 10V signal across
the transducer) and then started a timer running in the PIC (actually
just cleared it to 0). Wait a millisecond or so for the sending
transducer to quit "ringing" and to blank out the directly received
signal. I then turn on the interrupts and the ISR takes snapshots of
the timer and sticks them in a circular queue. At main level I just
crunch on the timer snapshot values at leisure. Granted this is not
ideal if you are seeking extreme precision, but it's plenty good enough
to help keep from running into things.

I'd like the range to be a bit more accurate than yours, probably 5-20
inches. What would you suggest is better to increase this - bandpsas
filtering (you sugggest this isn't all that important) or altering the
gain? What's the best way to alter the gain? Any particular components
(or at least, any specs I might need) for this?

You really need to have an oscilloscope for playing with this stuff.

I know, but they're not quite as cheap as a multimeter, so when I've
decided electronics is for me, I'll think about getting one

--
Danny

 

[Anthony Fremont]

"Danny T" <danny@nospam.oops> wrote in message
news:41ec0152$0$44979$ed2e19e4@ptn-nntp-reader04.plus.net...

Anthony Fremont wrote:

A scope is probably the best single instrument you can own for
tinkering
with this stuff. You can pick them up really cheap on e-bay. You
don't
need a 650Mhz tripple beam scope, but a dual trace with 20 - 50MHz
bandwidth would be nice for your
robotics/electronice/microcontroller
tinkering. You can get them so cheap that you could sell it if you
decide you don't like electronics and not really lose any money.

"so cheap"?
The one you linked to sold for nearly $300!

It was a real nice scope. ;-) The B&K somebody listed in
sci.electronics.equipment sold for $36.00.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=3866818287
I remember drooling over those when they came out. Look on e-bay,
there's tons of used scopes in great condition for cheap.