Easy DataLogger (for X and Y Plotter Routine, with Pen-Lift)
| The circuit below and
accompanying printed circuit board layout are for a simple
datalogger. Microchip's PIC16F88 microcontroller with incorporated
oscillator and analog to
digital converter is used to read the 0 -5 Volt output and penplotter
signal from instruments like the HP3581 Wave Analyzer, or the
Boonton 1120 Total Harmonic Distortion Analyzer.
A dual precision opamp, the Linear Tech LT1013 was used as a buffer for the XY inputs. Protection is provided with back-biased diodes. The pen-lift output is used to tell the data-logger whether the instrument has completed its scan. Resistor R6 is a pullup resistor. Typically, the pen-lift is connected with ground during the scan. A PIC16F88 was used for this circuit. Interface via RS232 is accomplished with a single transistor and 3 resistors. |
| Printed Circuit Board:
The printed circuit board is very straightforward. Full size is approximately 3.75 by 2.00 inches. Only one connection has to be made on the underside of the PCB.
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| The Software:
I adapted Martin Hebel's excellent StampDAQ software for use with the PIC16F84. The freeware is available on the Parallax Inc. website, www.parallax.com In the future I will use Selmaware's StampPlot Pro www.selmaware.com . The code was written in PicBasic to comply with the Stamp directives>
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