This article is very old, from around 2006. It was originally published on my old website, flylab.ovh.org, now defunct. It’s unlikely to have much educational value. I’ve republished it mainly for sentimental reasons. Grammar and style were left “as is”.
Introduction
It’s a simple, single channel electrical signal recorder, connected to the computer using serial port. The central part of the device is TLC549, integrated analog-to-digital converter. The schematic and the original software have been taken from Grzegorz Podgórski’s website (available in Polish only). The author has provided me the source code of his program, so I was able to do some modifications. I thank him so much for the code!
This device, because of its simplicity and low accuracy, can be used only for educational purposes. For example, it’s possible to use it as a support tool in school physical laboratory. The device can display to the students the shape of the sine wave, capacitor’s charging curve and so on. It can also be used to record the signals, which change slowly.
Construction
The device is connected to the computer by serial port (RS232). List of needed components:
- IC TLC549
- 3x Zener diode 5.1 V
- 3x resistor 10 kΩ
- 2x resistor 51 kΩ 1%
- diode 1N4148
- capacitor 1000 μF
- capacitor 0.1 μF
- switch
- 8-pin DIL support, universal PC board etc.
- RS232 cable, with DB9 female connector
Schematic is presented below:
The device was mounted on standard universal PC board. The Tic-Tac plastic box was used as the case. Photos below show the assembled device:
Software
The original software, written by the author of the website mentioned above, was slightly modified by me. I added trigger support. When it’s enabled, you can specify the voltage range. The signal is recorded if the measured voltage is within the range. It can be helpful with dealing with the one-shot signals.
You can select the time base: maximum 10 ms and so-called maximum probing frequency. If chosen, the oscilloscope works with the highest frequency possible. This time base is not specified and varies between machines. It depends on system load as well. On Pentium 2 GHz it was at the level of 7 kHz, 3.3 kHz with trigger enabled.
The software was developed with Delphi platform and runs on Windows systems. However, it’s possible to run it on Linux, using Wine software.