3. Schematic

posted Feb 3, 2010, 8:15 PM by Bill Bai   [ updated Feb 10, 2010, 7:33 PM ]
We used PCB Artist from Advanced Circuits to make the schematics and PCB layout for our boards.  Advanced Circuits is a PCB manufacturing company based in Colorado.  They do a bit of everything, but they have a really nice deal for students and everyone from ECET uses their service.  Their special deal for students is $33 for a double sided PCB up to 60 square inches, which is a pretty fantastic deal.  Not to mention a free and fairly powerful schematic/PCB software.

It's pretty hard to see the parts on the schematic above, but it's basically the circuit from Intersil Application Note 046 (attached to this and the last post, schematic from the app. note below).  There are some small changes and adaptations to make the PCB layout work better (1-pin headers for test points and 3-pin headers for potentiometers because the potentiometer footprints in PCB Artist suck), more pictures of parts of the schematic below.

The basic chip parts.  RC resonant circuit for the clock, battery, on/off switch, auto-zero and integrator capacitors, reference capacitor, etc.

7106 to LCD connections.

Over/Under Range Detection, Decimal Point detection circuitry

Switches for changing the resistors for various ranges

Register to keep track of what range the 7106 is in and the decoder to select the proper resistors for that range.
Bill Bai,
Feb 3, 2010, 8:30 PM