Conex Club Magazine - no.9-10 - 2002

Conex Club Magazine - no. 9-10 - 2002 - Methods and techniques for measuring conductive structures

Reading time: 4 minute

The main topics presented

1. Digital oscilloscope - a channel, for PC

An instrument for measuring and analyzing electrical signals to provide a so-called "measurement log" in graphical form, on paper, is particularly useful in laboratories for testing and analysis.

Considering the facilities / price ratio and the fact that a classic analog oscilloscope does not have the possibility to offer "anything else" besides the visual analysis of the moment, The digital oscilloscope interface for PC is a good investment for electronics.

The measuring and analysis device presented allows the analysis of signals in the time and frequency domain.

The interface connects to the parallel port of the computer, using its monitor as a viewing screen using Windows software. You can take screenshots of visualized signals and time and frequency analysis.

Technical data:

  • Number of channels: 1;
  • Frequency band: 0… 12MHz;
  • Input impedance: 1 MOhm / 30pF;
  • Sensitivity: 10mV… 3V / div .;
  • Sampling frequency: 800Hz… 32MHz,
  • Vertical resolution: 8 bits,
  • Optical input isolation,
  • Graphic landmarks for voltage, frequency and time;
  • Power supply through mains adapter 9… 10Vdc / 500mA;
  • Dimensions: 230x165x45mm;
  • Weight: 400g

2. Two-channel remote control receiver

The laboratory of Conex Electronic made a remote control receiver (CNX 192) with increased performance compared to the old version, namely with increased range.

The result was possible due to the use of an antenna preamplifier made with transistors with higher parameters such as BFR91A.

The receiver is designed to work with the two-channel remote transmitter - CNX 124 and can be used in various applications such as: control of doors and / or anti-theft device from vehicles, remote control of doors and gates in courtyards, access to garages, control of indoor or outdoor lighting and other multiple actuators .

Technical data:

  • Number of channels: 2;
  • Number of possible codes: 19683;
  • The device has two operating modes: momentary or bistable;
  • The control outputs are relay contacts with two working states each: normally closed (NI) or normally open (ND);
  • The contacts allow the control of currents up to 10A, at a voltage of 220V;
  • The device is powered from a stabilized 12V direct current source and consumes a maximum current of 100mA;
  • For the final assembly it is recommended to use the plastic box type KG518 (code 9605);
  • The appliance cannot be mounted in metal boxes!


  • with additional antenna - 50m;
  • with built-in antenna - 15m.

3. Security systems

The realities in the life of a society have imposed and require the assurance of a degree of "immunity" as high as possible, both human and material, in the face of what we call an undesirable event.

With technological progress, the diversity of situations that security systems must prevent or at least minimize the effects has expanded.

The existing products and services on the market are very diverse, and the choice is difficult, especially if there is no prior information.

The article will give an overview of the security systems used on a large scale. The subject being large, the presentation will be in the form of a series:

  • Background issues and current development trends of security systems;
  • Presentation of the main components;
  • News in the field.

4. Methods and techniques for measuring conductive structures

This article concludes the series of technological presentations dedicated to the evaluation of interconnection structures. If so far there have been articles related to the modeling, simulation and manufacture of printed circuits, it is time to make an introduction in the field of their measurement, in order to accurately inform on the signals that propagate and the disturbing phenomena that alter their shape.

Moreover, modern techniques in the field of time have the great advantage that they allow accurately detecting where there is a short circuit, an interruption or a discontinuity.

Although the article deals mainly the problem of PCB structures, some techniques can be successfully applied to all categories of transmission lines.

A special case is that of using techniques TDR (Time Domain Reflectometry) for detecting problems in the transmission of signals via cable TV.

5. Software timings made with C51 series microcontrollers

Timings made by the program, without the help of timers are used in almost all microprocessor applications due to the following advantages:

  • in the case of very short timers, with the durations of several car cycles, the loading, control and command instructions of the timers are avoided, which can last longer than the timing itself;
  • in case of large and very precise timings, of the order of seconds, minutes or hours, the jump time durations to the timer interrupt treatment subroutine and return to the main program are eliminated.

These times are uncontrollable, they depend on the instruction that is executed at the moment of triggering the timer interruption, knowing that the interruption is served according to the current instruction, which can last several car cycles.

6. Presence sensor with timer

The presented assembly offers, despite its simplicity, multiple possibilities of use in practice, from timed lighting of a light bulb on a ladder until mounted on an alarm module.

The notification of a person's presence is made by direct contact (with the "antenna" mounted in the field effect transistor grid).

The peculiarity, compared to the montages published so far in the specialized literature, consists in timed (adjustable) stop from notification of the event.

7. Programming alphanumeric LCD displays

The purpose of this article is to show you how to work with alphanumeric LCD displays that are controlled by the integrated controller. HD44780.

The communication protocol with the display is also called HD44780 protocol. Most alphanumeric LCD displays are based on this controller HD44780 patented and manufactured by Hitachi or other companies that produce it under the Hitachi license.

This article presents: a brief description of the LCD displays, the pinout of the alphanumeric LCD displays, the HD44780 instruction set, display examples, hardware implementation examples of the LCD displays, and user-defined character generation instructions.

8. FM receiver 88… 108MHz

The article presents the receiver for the 88… 108MHz band, made with the specialized integrated circuit TDA7000 in miniaturized execution (CNX-193).

The audition is done in a speaker with impedance of 4-8 Ohm and is supplied from a direct current source with a voltage of 4.5V, for example from a flashlight battery.

The integrated circuit is used as an audio frequency amplifier LM386N.

9. Reversible counter with memory

Continuing the series of applications with microcontrollers in the series AT90S1200, presents a "reversible memory counter" which has a set of four modes of operation and which can find applicability in different fields, for example, where necessary, counting certain events and executing commands after a certain number of cycles counting, user preset.

The counter has the possibility to read the pulses (on positive or negative level), present at the entrance of the assembly, at the terminal marked with IN, their counting and sending a pulse of 20ms, at the OUT output of the assembly, when the user-set threshold is reached during the counting process.

Pulse counting is performed on a 4-digit multiplexed display in the series TOF5461AH controlled by 4 transistors BC547 with the help of which the multiplexing is performed.

The microcontroller oscillator is made of valuable quartz crystal 11,0592 MHz and two fixed capacitors of 4,7 pF.

The main function of the counter is to count forward / backward on the positive or negative level of the pulses from the IN input of the assembly.


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