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.
Lots of information on robotics hobby sites
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!
A Cheap Ultrasonic Range Finder
Distance Sensing
devices for wireless distance and position determination useful as gesture controllers for robotic musical instruments
TL852 SONAR RANGING RECEIVER IC http://www.ortodoxism.ro/datasheets/texasinstruments/tl852.pdf
Cheap Sonar circuit schematic
Whole PARKING SONAR schematic with no special parts or programming
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