Electronics Projects - Short-Range Sonar with the BS2!

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| September 02, 2010

Basic Stamp Sonar

Just so you know, the following project is from the book: Programming and Customizing the Basic Stamp Computer. Click here, to read more about this title.

Note: This circuit requires the Basic Stamp 2, and 3 I/O ports of that Basic Stamp.

This project is best suited for use as a sensor on a robot. This circuit will actually allow you to measure distances from an object. It measures in a 'unit' and it's range is about 10 inches. As the receiver and transmitter, you will use an ultrasonic transmitter and receiver pair tuned to 40khz (see parts list below.) The circuit is very easy to build, and you can build it on whatever you have laying around. I assembled it onto a Radio Shack pre-etched circuit board - and it only took up about an inch and a half square.

parts:

Resistors (1/4 watt, 10% or better)
R1, R5, R6, R11, R19, R21	10K	Jameco: 29911 DCkits: CF25-10K
R2, R7	47K	Jameco: 31149 DCkits: CF25-47K
R3, R8	22K	Jameco: 30453 DCkits: CF25-22K
R4, R9, R14, R18	100K	Jameco: 29997 DCkits: CF25-100K
R10	18K	Jameco: ------- DCkits: CF25-18K
R12, R13, R16, R17	220K	Jameco: 30525 DCkits: CF25-220K
R20	1k	Jameco: 29663 DCkits: CF25-1K
Other Components:
C1, C4	0.1uf ceramic cap 50WVDC	Jameco: 151116 DCkits: 21ET100
RCVR, XMTR	40khz ultrasonic receiver and transmitter	Jameco: 136653 DCkits: --------
U1	LM358AN dual op amp	Jameco: 120862 DCkits: --------
U2	LM339N quad comparator	Jameco: 23851 DCkits: LM339
XTAL	40khz quartz crystal	Digikey: SE3316-ND

The schematics are below. Make sure you connect everything correctly, then after that is done move onto the basic stamp code below. Click on the thumbnails to enlarge the schematics.

Basic Stamp Code:

What will it do?
It will open a debug window in the basic stamp compiller, and display distance readings (in 'units') from the circuit.

Please note that the 'Free Stamp Pin' in the schematics refer to the basic stamp i/o port that you connect that part of the circuit to. You will need to look out for the the three (!!!! FREE STAMP PIN ' ' !!!!)'s in the code, and change the X's that accompany them to the correct i/o port number. Download the source code by

1.) Right-click on the link and select 'Save Target As..' (Windows)

2.) Click on the link, and hold it until a menu pops up, and select 'Save Target As...' (Mac)

bs2sonar.txt
OR
bs2sonar.bs2

Refer to the SmallBot Programs page to see how to implement this circuit as an ultrasonic sensor for your robot.

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