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.
It’s a simple, single channel electrical signal recorder, connected to the computer via serial port. The central part of the device is TLC549, an analog-to-digital converter. The schematic and the original PC software have been taken from Grzegorz Podgórski’s website (archived, 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 show the students the shape of the sine wave, the 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 — RS-232. List of required components:
- TLC549
- 3x Zener diode 5.1 V
- 3x resistor 10 kΩ
- 2x resistor 51 kΩ 1%
- diode 1N4148
- capacitor 1000 μF at least 6.3 V
- capacitor 0.1 μF
- switch
- 8-pin DIL support, universal prototyping board etc.
- RS-232 cable, with DB9 female connector
Schematic is presented below:
The device was assembled on standard universal PC board. The Tic-Tac plastic box was used as the outer cabinet. Photos below show the assembled device:
Software for PC
The original software, written by Grzegorz Podgórski, was slightly modified by me. I added trigger support. When it’s enabled, you can specify the voltage range, in which the signal is recorded. When the signal is out of this range, the recorder stops recording. It can be useful when dealing with the one-shot signals.
You can select the time base: minimum 10 ms and also maximum probing frequency. If maximum is selected, the oscilloscope works with the highest frequency possible. This frequency may vary depending on the CPU model and system load. On Pentium 2 GHz, its was about 7 kHz, 3.3 kHz with trigger enabled.
The software was developed in Delphi platform and runs on Windows systems. However, it’s possible to run it on Linux, using Wine software.