These sonar modules don't perform as good as the Devantech SRF04, however these units cost only about 1/8 as much!
The Ultrasonic Transducers are as of this writing July 2004, available from Electronic Goldine . The part number is G951, 24khz units that cost $1.50.
My modules use a MAX489 serial transceiver chip to generate a +- 5 volt signal driving the output transducer. This is about 1/2 that is used for the Devantech which uses a RS232 chip. The Devantech also use's several more amplification stages for amping up the echo back. The end result its able to see out over 10 feet where as my system can do about 4 feet. For small robots this is still all that is typically useful anyway. Perhaps some time in the future I'll make a new and improved design.
My original sonar boards are made with my CNC machine tool that can cut out the traces in the copper of the PC board. This is why they look strange in the photos. However you should be able to etch your own using common print and chemical etch methods. The best results of course would be to send the Gerber files to a mail order PC board shop. The boards are fairly small and you should be able to have quite a few made up at little cost, with good quality results.
Be sure to Left click the file links to Save As, otherwise if you right click the web browser will simply show you the contents of the files which are all Text files!
The text side in HPGL, any drawing program such as CorelDraw! can read this. Use it to print out and maybe acid etch.
The copper trace side in HPGL, again maybe you would prefer to etch the board with this file.
The Gerber file of the top side of the board, in case you have to use a double sided PCB. This file should be usable at any mail
order PC board fab shop
The Gerber file for the trace side of the board, again maybe if you want to use a board shop to make the board.
The Excelon drill file a PC board shop would use to drill the holes.
Aperture file for Gerber production
This file tells the PC board house about the size of the pads and traces for the Gerber files
If you have any other CNC motion control software you may be able to convert the files, or use the HPGL files.
The DanCad file for actually cutting out the copper traces. Its setup so after you cut the traces and drill the holes you
use the mounting holes as a reference, just flip the board and run the file to engrave the text side.
The DanCad file to engrave the component side with text. The text is only about .07" tall so very fine cutter.
The DanCad through component drill hole file, .032"
The DanCad file to drill the board mount holes .125"
Simple test program in Pic Basic Pro, source code
The text file of a basic program for a PIC 16F628, if your using the Amtel with a basic program language you could perhaps
adapt some of of the code to work for your chip
Compiled HEX code for PIC16F628
Assembler code from Pic Basic .
On the header plug:
E is the Echo pulse back
T is the 24khz signal from you micro chip
P is + 5 volts power
G is ground
R1 is 100K ohm
R2 is 10K ohm
LM386 is a audio amp
MAX489 is a RS485 serial driver, I had some I scraped from some boards, that's why I used this chip.
The transducers are double sided foam taped to the soldered copper side
and a short bit if wire is soldered to a trace to the transducer leads
to transfer the connection from the copper side to the component side.
If you CNC the traces be sure to drill .125" holes where the transducer leads go though to be sure the leads don't touch any left over copper.
The micro processor sends at 24khz pulse to pin T, this then goes though
the MAX489 to produce a flipping differential voltage to the Transmitter
transducer to produce the maximum sound burst.
The 2N3904 is a NPN transistor, with the lower pot controls the point
where an amplified echo from the LM386 audio amp is 'loud' enough to be
considered valid, generateing a logic level high.
Both pots are 10k ohm, set pot near the Transmitter to about .4 volts, the upper pot adjusts the gain, usually set it to just about max output.
Have your code generate at least 8 pulses at 24khz to be sure every
thing is resonating. Then stop the pulse and have the micro count
time it takes for the sound to come back, assuming it does. Based on the speed of sound that should be the distance to the object seen.
Good luck on your own home made sonars!
Loveland Colorado, USA