Conex Club Magazine - no.1 - 2006

Conex Club Magazine - No. 1 - 2006 - Fuzzy Controllers

Reading time: 4 minute

The main topics presented

1. Alternative technologies for connecting electronic components (I)

The article intends to serialize the issue of alternative technologies regarding the connection of electronic components to the printed circuit board by solutions to eliminate hazardous substances from the electronics industry.

Thus, the reader will be familiar with the practical engineering aspects of the optimal implementation of the Directive European RoHS (Restriction of Hazardous Substances - restrictions on the use of certain hazardous substances) in Romania, especially to evaluate and optimize the implementation of conductive adhesives and lead-free alloys in the Romanian electronics industry.

The rules on which the directive is based implement the European Parliament's requirements on restrictions on the use of certain hazardous substances in electrical and electronic equipment. (2002/95 / EC - RoHS Directive).

The rules prohibit the placing on the European market of new electrical and electronic equipment (EEE) containing higher levels than those established for: lead, cadmium, mercury, hexavalent chromium and PBB and PBDE flame retardants in the components of printed circuit boards.

2. Very low voltage stabilizer (LDO) 1.2V

They are electronic devices that are powered by a single source of electricity (a 1.5V battery or 1.2V NiCd battery). The voltage of a new battery can be 1.65V (sometimes 1.7).

It is considered that a battery is still usable when the voltage drops to 1.2V, about as much as a NiCd battery.

There is a voltage stabilizer that offers a stabilized fixed voltage of 1.15V when the value of the supply voltage varies within the limits of 1.2… 1.8V.

The value of the output voltage does not change by more than 70mV at a load current of 5mA. It is a scheme of LDO stabilizer (small input-output voltage drop).

3. Fuzzy controller

Multiple opportunities have emerged in the field of digitally controlled systems with the development of microcomputers.

Digitally retrieved information is quickly processed. Complex systems are easy to control. A new approach has been introduced in automation using Fuzzy logic controllers.

The expert familiar with a certain process can easily implement the desired solution just by simply writing and / or modifying the code.

Digital control

Digital control offers new opportunities that analog controllers are not able to offer (or are difficult to implement): data acquisition, system identification, adaptive control, etc. (topics known from the theory of digital control).

Two important terms are related to digital systems: time discretization (sampling time) and quantization by level. The sampling rate defines the successive moments in which the sampling of the continuous values ​​takes place. Quantization occurs as a result of A / D conversion.

The intelligent control application can be explained as the need to make an adjustment of the physical size pursued in the following conditions:

  • In real systems, different perturbations influence the constant result;
  • The real processes, in most cases, are nonlinear;
  • The processes are modifiable over time.

These requirements are often met in everyday life. Digital control is therefore necessary.

FLC design phases

Fuzzy logic controllers (FLC) are an example of a control like the one explained above. They fit very well with systems that are difficult to model.

The design phases of Fuzzy regulators are:

  1. Process analysis;
  2. Determination of the rule by an expert;
  3. Fuzzy controller simulation.
  4. If the desired results are not obtained, steps 1, 2 and 3 must be repeated.

Realization of the FLC in a system with digital control consists of writing the source code (the C language is used in the example in this article). Based on the given temperature, the controller reaches the desired value and maintains it until a request for another value made by the user appears.

Before writing the program code it is necessary to analyze (and monitor) the system with specific control. It is desirable to describe the mathematical system, to simulate the process using a microcontroller and then to implement the program.

The purpose of the simulation is to use mathematical algorithms that try to describe operations in a real system. Thus, it can be verified whether the control algorithm meets the requirements in reality. Usually the initial conditions are given in the time domain. The advantages of such a system are: stability, accuracy and speed.

4. Mini transmitter (modulator) FM 100 - 108MHz

It presents a Velleman kit that can be used in various applications such as baby surveillance, FM tuner testing, private communications, etc.

With this miniature transmitter you can make a "radio link" at a distance of the order of a 20… 50 meters, in the 100… 108 MHz band.

The transmitter is frequency modulated. To make the connection you also need a receiver in the UUS band for radio stations with frequency modulation (FM), ie for the band 88… 108MHz. The electrical diagram is presented in figure 1 (from the article) and the location of the components and the drawing of the wiring printed in figure 2 (from the article).

The microphone amplifier (see wiring diagram) is made with transistors T2 and T3. The degree of modulation is established with the help of the semi-adjustable potentiometer R4. Frequency modulation is performed using the varicap diode D1-BB221.

5. 2x30W stereo amplifier

The K4003 audio (stereo) amplifier, although very compact, offers a high quality signal and a relatively high power at the outputs, thanks to the use of the monolithic integrated circuit type TDA1521.

The assembly is easy to do and requires a small number of auxiliary components. The total amplification, for each channel, is 30dB, (about 32 times).

The printed circuit board has the dimensions of 50 x 70mm. The amplifier, more precisely the integrated circuit TDA1521, requires a proper radiator.

Technical data:

  • Power supply: 2 x 12V;
  • Maximum RMS power: 2 x 15W / 4 Ohms; 2 x 10W / 8 Ohm.
  • Maximum musical power: 2 x 30W / 4 Ohm;
  • Sensitivity: 300mV / 20 KOhm;
  • Frequency band: 7Hz… 60 kHz (-3dB);
  • Signal to noise ratio: 98db;
  • Crosstalk: -70db;
  • Overload and short circuit protection (max. 1 hour).

6. Source of constant current, power

An application for power electronics is presented, constant current source 0-5A, useful for the correct charging of some accumulator batteries or the supply of some lamps for which it is desired to maintain the color temperature.

7. Determinant 4001 - Identifier / tester for transistors

The instrument presented in the article ensures the identification of the type of transistor, the arrangement of the terminals in the capsule or the amplification factor.

An application that can be approached as a work to support the certificate at the end of the school year can also be a test bench for electronic components.

A modern and fast way to identify the type of transistor, the arrangement of the terminals in its capsule or some electrical parameters, is an application already famous in Europe, first known as "Determinator 4001" (and published in Electronique Pratique no. 282 - April 2004, with PIC16F872 uC) and then revised (upgraded) as "SC-Analyzer 2005" (and published in Elektor No. 2/2005, with PIC16F876 uC). The developer of the application is Michel Waleczek.

8. Universal temperature sensor with LM335

Using the particularity of the LM335 temperature sensor, respectively the linearity of the voltage output with a slope of 10mV / ° C, Velleman has developed a universal temperature sensor module, type "3 wires", with unified signal output 0… 5V or 0… 10V (on a 20mA current loop).

Technical data:

  • 3-wire type module: GND, + V and OUT;
  • accuracy: 2 ° C at the end of the range;
  • measuring range: 20… 70 ° C;
  • current on the output loop: 0… 20mA (the loop closes with resistors);
  • maximum voltage on the loop: 10V;
  • supply voltage: 12Vdc for OUT = 0… 5V or 15Vdc for OUT = 0… 10V;
  • current consumption: max. 30mA.


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