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Sci.Electronics.Basics -> Parking Sensors
There are 5 messages in this thread.
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Author: MichaelDate: 18:09 24-12-07
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Hi,
I'm looking at parking sensors and can't work out why there aren't lists of
sites on Google telling you how to make homemade versions. Surely all you
need is an array of ultrasonic sensors each one "pinged" in turn to avoid
interference and then read the distance values into a uC for
analysis........or am I missing something?
Cheers,
Michael
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Author: Sjouke BurryDate: 20:26 24-12-07
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Michael wrote:
> Hi,
>
> I'm looking at parking sensors and can't work out why there aren't lists of
> sites on Google telling you how to make homemade versions. Surely all you
> need is an array of ultrasonic sensors each one "pinged" in turn to avoid
> interference and then read the distance values into a uC for
> analysis........or am I missing something?
>
> Cheers,
>
> Michael
>
>
Just some months ago I took one apart.
One exponential horn(~1 inch cross)as transmitter, and
another such horn as receiver.
I think you can buy tweeters looking like that.
Opening angle about 120(+/-60)degrees opening angle.
Copper/ceramic disks such as in most beepers as transmitter
and receiver.
the following method was used in a kodak automatic focus camera
in the dark ages(~1975??) and obviously broke down when
photographing through a windowpane :) .
Usable range was about 10m (11-12yards).
Transmit ~ 2-6 bursts per second, 1 msec long, ~20-50 KHZ.
1 msec is about 150mm(150 out,150 back,300mm/msec sound speed).
I would advice to use 3 analog multipliers to multiply
the incoming signal with the 4'thpower of time, or in other words,
use a sawtooth signal to start with, feed that to both inputs
of the first multiplier,output to the second multiplier, then feed
receiver and 4'th power sawtooth to the third multiplier.
That way your return signal strength on the timescale will be nearly
constant, only the noise will rise with increasing distance,
until the signal becomes useless.
Then trigger on that, and measure time to get distance.
Also the amplitude of your sawtooth at the trigger moment, stands
for time/distance measured.
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Author: defaultDate: 11:26 25-12-07
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On Mon, 24 Dec 2007 23:09:00 GMT, "Michael"
<mQiQcQhQaQeQlQ@QmQhQiQmQsQ.QcQoQ.QuQkQ> wrote:
>Hi,
>
>I'm looking at parking sensors and can't work out why there aren't lists of
>sites on Google telling you how to make homemade versions. Surely all you
>need is an array of ultrasonic sensors each one "pinged" in turn to avoid
>interference and then read the distance values into a uC for
>analysis........or am I missing something?
>
>Cheers,
>
>Michael
>
Lots of information on robotics hobby sites
http://www.sparkfun.com/commerce/product_info.php?products_id=8502#
Ultrasonic Range Finder - Maxbotix LV-EZ0
SKU#: SEN-08502
Price: $24.95
Description: This is the fantastically easy to use sensor from
Maxbotix. We are extremely pleased with the size, quality, and ease of
use of this little range finder. The serial interface is a bit odd
(it's RS232 instead of standard TTL), but the PWM and Analog
interfaces will allow any micro to listen easily enough. The sensor
provides very accurate readings of 0 to 255 inches (0 to 6.45m) in 1
inch increments with little or no dead zone!
--
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Author: defaultDate: 11:42 25-12-07
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Author: defaultDate: 13:22 25-12-07
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