We can use a PC for connecting the homemade data acquisition hardware and produce the GUI for user friendly graphical presentation easily. One of the project that uses Visual Basic is the Data Acquisition & Logging System using AT89C51 made by Abbas Raza. In this project we use a PC for GUI display and the homemade data converter board using the AVR microcontroller. The circuit is built with the ATmega8. The chip has the onchip 10-bit resolution A/D Converter. Temperature sensor are connected to the 6 channels ADC input. You can connect up to 8 sensors with the ATmega8 TQFP package. The analog inputs are captured by sending a command from PC. The readings will display graphically or text data. The data can also be recorded as the database.
The complete hardware schematic for the ADC board is shown in Figure 1. The board consists of the ATmega8, the temperature sensor (LM335), and the serial interface. The on chip firmware controls reading the ADC converter, receives commands from PC and sends the reading to PC. The microcontroller is running with 8MHz crystal oscillator, if we use the internal RC oscillator, the external crystal may be omitted. The ATmega8 DIP version has 6 channels analog input. If you need up to 8 ADC input, you can use ATmega8 in TQFP package, or you can use another AVR microcontroller with the on-chip ADC.
We use LM335 temperature sensor. It can measure the temperature using two wires remotely. The chip produces an output signal that is proportional to the Celcius temperature scale. The trimmer POT is used to calibrate the correct output voltage at known temperature, for example 2.98V @ 25° C.
Features of the software are as follows.
- Adjustable sampling interval,
- Real time view in single graph or multiple graph,
- Record the data, save, and open the recorded database,
- Get statistically reading, print the record and graph (or export it as the metafile, JPG),
- Serial control window for monitoring and manually data transfer.
The full version PC software is designed for capturing up to 16 channels. In this version, the PC software will read 8 channels. For the ATmega8 in DIP version, it can display only 6 channels.
For more detail: Data Acquisition System using ATmega8