Subject:
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Re: Has anyone built this homebrew sonar ranging board?
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sun, 1 Jun 1997 01:03:07 GMT
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Original-From:
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root <ROOT@SNOTNOSE.WIZARD.spamcakeORG>
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Viewed:
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1627 times
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> http://www.vnet.net/wizorg/sonardoc.html
> It's a system similiar to the Polaroid 6500, but costs <$10 to build.
> Has anyone done it?
I have :)
> Should I try it and share the results? (of course I should!)
What would you like to know about it?
> Does anyone see any major drawbacks after reading that, as compared to
> the Polaroid 6500?
Here are the essential pros and cons (note that I have NOT ever actually
had a Polaroid to mess with so my comments are based on what I've read
about it and other people's comments):
EL-CHEAPO SONAR
- Price: Very cheap. The detector is based on a NE567 tone
decoder. The ranging portion can either be built
with discrete components or a PIC processor.
- Max Range: 8-10 feet with careful tuning and attention to
detail when placing the transducers.
- Min Range: Appears to be about 1 inch or so depending on the
minimum timing interval basically.
- Power: 5-18 volts. Not critical. The only change for an
alternate voltage is for the resistor limiting
current through the transmit transducer and the
resistor to adjust the output to a suitable level.
- Interface: Detector uses 4 wires, +V, GND, TX, RX
Ranger (both types) offer digital outputs although
you might want to add an additional 74373 or similar
for hooking to a CPU. In the PIC version you are
free to program the interface anyway you like it.
Two additional pins are free for handshaking.
I designed the EL-CHEAPO SONAR setup because I didn't have the money to
buy
Polaroid units and because I just wanted to see if I could do it. The
PIC
version is not all there yet software-wise. I worked it out just enough
to
prove it worked and then moved on to the next step of designing the
robot's
controller board. Now that the board's done I will be getting back to
the PIC
stuff as soon as I get it tested and installed since I'll be needing it
myself
then. Necessity has such a wonderful way of altering one's priorities :)
Check
back on my page (http://www.vnet/net/wizorg) in a month or two and see
if
I've gotten better PIC code up yet.
Another thing- after checking out the Handyboard a bit I think you could
probably control the transmitter/detector portion directly from the
Handyboard
without either of the ranging circuits. In fact, the transmit stuff is
already
there. Of course you would have to handle the software on your own but
the
algorithm is simple enough. A potential modification would be to alter
the
detector so it ramped the gain over time. From experiments with the
circuit,
I suspect you could probably achieve a range of maybe 15-18 feet that
way.
But it would take some work I think.
POLAROID SONAR
- Price: $50-75 bucks depending on where you buy.
- Max Range: 25-35 feet so I've heard
- Min Range: 15-18 inches, again from what I've heard
- Power: Not Sure
- Interface: Analog/Digital I think
The Polaroid module generally seems to be the superior unit. Of course
it
costs considerably more also. Also it suffers a bit on the low-end of
its
ranging ability, which in my opinion is a serious limitation, and it
doesn't
interface to a host CPU quite as easily (not that its particularly
difficult
either). Otherwise, if you have the money to toss at it, its probably
the
better way to go. You could of course always augment it with the cheaper
version to make up for the minimum range thing. The EL-CHEAPO circuit
though
would probably make a very useful IR Proximity-type sensor.
> Is there another place to pick up the Polaroid 6500 ranging sonar
> besides WIRZ.com? (He's shutting down business for a few weeks to
> move...)
Of this I have no knowledge, sorry :)
> Thanks,
> -=Fred Cass=-
>
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