What it is?
The project is useful for electronics enthusiasts passionate about radio frequency and more. It can measure capacities with fairly good accuracy, between 1pF and 100nF using an RS232 serial interface. The measured value is displayed on the PC or laptop display.
How does the project work?
The NE555 integrated circuit is powered directly from the RS232 serial interface. It generates rectangular signals at a frequency of 3.5kHz, which are received by the CTS input of the interface.
List of required components:
1 x R1 = 10k
1 x R2 = 47k
1 x C1 3,3nF
1 x C2 = 100nF
1 x NE555
1 x DB9 mama serial plug
2 x two DB9 serial plugs (one father, one mother) for designing the serial cable
1 x Electronic test board + connecting wires
How do we use the interactive interface?
As can be seen in the image below, the driver for the serial plug can be identified by 4 communication ports. This way, there will be no problems not identifying the driver.
"Nullpunkt" is the "0" calibration button. Basically, when the assembly is put into operation with the measuring wires unconnected, it is possible that the displayed value switches between 0pF and 2pF. For a more accurate measurement, when we catch "0", we press "Nullpunkt".
Download the interactive interface (software)
For a better understanding of the operation of the circuit and to make this assembly on the breadboard we will need electronic scheme presented below:
How do we connect the DB9 serial plug to the assembly?
Pin description table for DB9 serial plug
The serial connection mode between the father and mother sockets
Download the manual and the electronic diagram
An example of a measurement for a 10nF polystyrene capacitor is shown below: