Serial Port (RS232) DAQ

 

I have received e-mails from many people asking for a circuit that could be plugged to a PC’s serial port.  I have being doing

Some research on this subject, and I am still doing so.  In the mean time let me offer you a simple circuit that can plug to any

IBM compatible PC with a serial port (RS232).  This circuit is NOT REAL RS232 communication, because it doesn’t use

the RXD and TXD lines, but the handshake lines.  Yet it is cheap, easy to build and it will fit some of your Data Logging needs.  Using the well known ADC0804 (like on my other projects Parallel Port DAQ or Data Logging with a Macintosh Powerbook 160 using a 386SX) and a modified version (V3.0) of my SoftDAQ data acquisition software I made a setup to

show how to measure weight, force or pressure (the same fundamentals apply to all of them). Using a “sandwich” of  two copper plates and a layer of conductive foam (like the one some static sensitive-devices like CMOS or FETs come with).

Basically it is a resistance which changes proportionally to the unitary deformation of the foam.  One can obtain a multiplying

constant value from empiric tests.  This is my setup:

 

 

 

The software runs on a 386DX laptop with Win 3.1.  But it will run on Win95 or Win98.  Below is the schematic: