Ultrasonic transmitter/receiver application question

RichardF

I am interested in working with ultrasonics and the Propeller chip. I have ordered from Jameco a 40 KHz transmitter and receiver pair under Mfg part number 40TR16F. I can't find· a data sheet which tells me the specifics of how to input the transmitter and output the receiver. Any help on this would be appreciated.
Thanks,
Richard

Franklin

This might help http://www.interq.or.jp/japan/se-inoue/e_sonic1_3.htm·there are other links Googling for "ultrasonic sensor circuit" (WOTQ)

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- Stephen

PJAllen

http://www.discovercircuits.com/DJ-Circuits/40kultrasoundrvr2.htm
http://www.discovercircuits.com/DJ-Circuits/ultra40khzxtr1.htm

Beau Schwabe

Just my 2 cents....

What I don't like about "fixed" 40 kHz generators is that they're not always optimized to the resonant frequency of the transmitter or receiver.

PJ Allen's receiver has the right idea, in that the front end is a tuned circuit to 40 kHz, but the actual resonant frequency of the receiver transducer may not be right at 40 kHz.

Not as critical, but the transmitter transducer also has an optimal resonant frequency that may not exactly be right at 40 kHz. In an ideal situation you would want your ultrasonic transmitter and receiver transducers matched to the same frequency. Some empirical testing is required to determine the optimal frequency by sweeping the frequency and noting the response curve characteristics.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

RichardF

Thanks all,
Thats enough to keep me busy for awhile.
Richard

LoopyByteloose

I've wondered if audio tweeters might be adapted to provide a higher wattage output on the transmitter side. If so, they would certainly extend the physical distances that the sensor could manage.

In fact, there really is no reason that audio tweeters cannot be used as reciever sensors if they respond to ranges that high. After all audio speaker can make reasonable audio microphones and are often put to dual purposes in intercom systems.

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RichardF

Kramer,
Can audio tweeters go above 20 KHz? I am not hardover about 40 Khz. I just wanted to play around with communications between microcontrollers using frequencies above the human hearing range. I also am interested in the underwater comms aspect also. As you know I am working the tethered submersible ROV and I would like to be able do some comms there.
Richard

MSDTech

Some of the "super" audo tweeters can go to 40khz, or at least so they claim:
http://www.adelcom.net/MOTOROLA_ksn1016a.htm

I know some stero systems from the late 60's and early 70's had frequency response curves to 100 khz. I have one, the Dynaco Stereo 120 was rated to 100khz. They were using one as a power driver on an ultrasonic unit in the lab at collage.


Post Edited (MSDTech) : 4/27/2008 12:29:10 PM GMT

RichardF

Thanks, MSDTech. Now I have to learn how to interface a BS2 to a 50 Watt speaker!
Richard

RichardF

Imagine this! I did some experimenting with my 8 dollar set of JAMECO ultrasonic sensors (part # 136654) and I was amazed at how simple a setup will work. I drove·one sensor (transmit)·directly from an output pin on my BS2SX through a .1 uf capacitor, and setup a receive sensor to my BS2SX through an LM364 audio amp (200 gain) to an input pin via a 250 uf capacitor, and walla!, it works out to 3 feet. Heres the code:

' {$STAMP BS2sx}
' {$PBASIC 2.5}
InPin PIN 8
DO
· FREQOUT 9,1 ,16000
· IF InPin THEN FREQOUT 13,1,1800
· LOOP

pin 13 feeds a piezo speaker. From 3 feet out wave most anything in front of the ultrasonic sensor pair and you get beeps.

Maybe not so useful, but interesting that it will work so simply.

Mike Green

Yeah. Isn't it interesting how simple cases often work simply. The complexity is in getting more output power for more range, getting more input amplification with AGC (automatic gain control) so it works well over a wide range of input signals, more selectivity to reduce sensitivity to noise, etc. On the other hand, a range of 3 feet covers most of the needs for non-contact obstacle sensing.