Compass Circuits

Digi-Compass Update

Oct 28, 1989



ATTENTION DIGI-COMPASS BUILDERS:



DIGI-COMPASS Corrections/Update

Nov 89 Radio Electronics



Please make the following corrections to your Digi-Compass

Text:



Schematic, Pg 45:



      VCC (5.0V) should be shown at IC4 (LM7805) output

      and VDD (6.8V) should be shown at "C5+".  If con-

      nected as shown IC3 may be damaged.  



      VDD should be labeled "6.8V" and not "6.5V".  This

      voltage should be +/-.4V on your circuit for best

      operation.



      IC3, the TLC548, has pins 2 and 3 swapped.  Pin 2

      is "INP" and Pin 3 is "REF -".  Weird but harmless 

      operation will occur if connected as shown.



Text, Pg 51:



      The number of data acquisition averages is changed 

      by pushing the Greater-Than (>) or Less-Than (<) keys,

      not the Open or Closed Quote Keys.



Text, Pg 82:



      The standard command line syntax example for TEXTCOMP

      is misleading.  Spaces must be included between 

      arguments.  Therefore, the example should read:

                        TEXTCOMP LPTn 10







I understand that Radio Shack has dropped the TLC548 ADC IC 

used in my Digi-Compass project.  When I designed the inter-

face I deliberatly used this part because I wanted to use 

readily available IC's (did you know that every piece of 

hardware except the optocouplers came from Radio Shack?).

The project was designed in DEC '88 and Radio Shack had no 

plans to drop any of the parts at that time.



I suggest you try all of the Radio Shacks in your area to see

if the ADC is in their junk-box stock (part #276-1796).  If 

this route fails, I will supply the part for $6.95.  



Also, for those who do not want to download the software file

may purchase it from me for $6.00.  This may be cheaper than 

downloading the 100K file at 1200 baud from RE BBS.  It will

be supplied on a 360K PC data diskette.



Please follow this ordering procedure:



      Send check or money order only (CA Residents add TAX 6.5%) 

      plus $1.75 shipping and handling to -



                  Digital Products Company

                  Thomas E. Black

                  134 Windstar Circle

                  Folsom, Ca 95630



I will try to send your parts out within 48 hours via standard US

mail.  If the response is too tremendous this time may be much

longer.  If I run out of parts then I will return your payment 

as received.  This offer is subject to change and is for a short

time only.



If you have other Digi-Compass parts needs please write me!  I 

may be able to help.  Perhaps you lack software experience and

need some specialized code for your application.  For a reason-

able fee I may be able to supply custom software.  Please include

a Stamped and Self-Addressed Envelope with your correspondence.



Please avoid calling, but if you have to then expect any return

call to be collect (I'm a very small business with limited 

resources).  You will most likely have to leave a message on an

answering machine - expect a weekday return call around 7-8PM PST,

or much earlier if on the weekends.



Believe me, this project is worth the frustration!  It works well

and has unlimited applications.  Please write if you have any

software or applications to share.