Subject:
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Re: Help!! Polaroid problem!!!
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 23 Apr 1998 01:52:03 GMT
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Original-From:
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David Kott <dakott@alpha.delta.edu=NoMoreSpam=>
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Viewed:
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381 times
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On Tue, 21 Apr 1998, Chris Moylan wrote:
> microcontroller is virtually identical at the lowest level. The problem
> is when we attach the device to the scope, we NEVER see any significant
> voltage on the ECHO pin. With the INIT pulsing 5V every second, we
> still get nothing but residual noise (kind of a lot, but at no more
residual noise? It was my understanding that the Polaroid module used
pulse time differentials to relay distance information. One need only
look at the difference in time, between the leading edge of the init
pulse, and the leading edge of the echo pulse to determine the distance
from an object. This is different from modules that generate a variable
voltage between two limits proportional to the Time of Flight of a given
ping. When you say "noise", it makes me think that you are dismissing
the actual Time of Flight information as a glitch in the output. You
should see about .9 ms between the leading edge of the init pulse and
the falling edge of the echo pulse for every foot between your transducer
and a given target.
Someone please correct and clarify this if I am wrong. I don't remember
specifically what version of the classic Polaroid transducer
driver/detector we used, and Chris may be using a different one.
> than .5V)and the remnants of the sixteen pulses from the ping. I hear
> a clicking sound too, which was unexpected and is quite annoying. Is
> this normal? How come I never have any voltage on ECHO? I am not
Every transducer I have ever used has had a human audible component that
was heard every time the transducer emitted a ping. I think this is
called "ringing", and is due to the emitter plate flexing, and generating
harmonics which may fall into the human audio range. Check out the
Fourier transform of a digital pulse and you can see the frequency
components that we hear.
> using the blanking inhibit at all, and if I look at the noise at about
> a 200mv setting on the scope, I can see a shape in the noise that
> changes with an objects proximity to the transducer, but it is not
> anything like a logic level. I have tried a million different ways of
Could your scope leads be a bit flaky? How are you triggering? If you
are using a digital scope, try and configure the instrument for "manual"
trigger, as opposed to "auto" trigger. There will most likely be a
variable setting to allow you to set the trigger threshold. All the
digital Tek's do this. I seem to recall it being under the "Vertical
Menu", or was it "Acquire"? *shrug* Then attempt to "capture" the echo
edge event. It was a 5 volt signal; have no doubts there.
<snip>
> way to test it. We connected it to the microcontroller as it connects
> to the handyboard, but that of course didn't work either. If you can
How did you connect it to your Micro? Again, the device we used did not
supply an analogish level to represent the Time of Flight of a given
audionic pulse. The time information was determined by measuring the
difference between the init pulse and the echo pulse with an Input
Capture. With a 2 Mhz E-clock, the magic number turned out to be about
150 TPU counts per foot. I don't remember precisely how we got that..
probably trial and error.
> respond via email, that would be best because I don't get this list
> regularly. Please respond soon so I don't fail senior design!! ;-)
Note that I have forwarded my response to the Handyboard list as well.
Have faith, and good luck.
-d
The Fourth Law of Programming:
Anything that CAN go wrong wi
/kernel: pid 128 (sendmail), uid 0: exited on signal 11 (core dumped)
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Message has 1 Reply:
 | | Re: Help!! Polaroid problem!!!
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| Hey, I just wanted to thank everybody for there help with this, it did turn out to be the pull up resistor problem, I feel like a moron. We used the handyboardy sonar interfacing schematic when we wired it up and failed to realize that we aren't (...) (26 years ago, 23-Apr-98, to lugnet.robotics.handyboard)
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Message is in Reply To:
| | Help!! Polaroid problem!!!
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| I am trying to use one of the Polaroid 6500 kits from Wirz with my senior design project. It doesn't exactly use a handyboard, but our microcontroller is virtually identical at the lowest level. The problem is when we attach the device to the scope, (...) (26 years ago, 21-Apr-98, to lugnet.robotics.handyboard)
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