Conex Club Magazine - no.12 - 2002

Conex Club Magazine - no.12 - 2002 - TDA1562Q - 70W H-class audio amplifier

Reading time: 4 minute

The main topics presented

1. Function generator for PC 0.01Hz… 1MHz

It presents a modern tool for generating signals with standard or predefined waveforms, indispensable in research and design laboratories.

Generating an electrical signal involves, in most cases, the use of specialized integrated circuits, capable of synthesizing standard waveforms. (sinusoidal, rectangular or triangular) in a restricted amplitude and frequency range.

Modifying the standard waveforms to your own needs is difficult, through changes in the wiring diagram of the generator used, and the final result is not always as expected.

High precision values ​​for amplitude and frequency involve expensive measuring devices.

The function generator presented allows obtaining both standard waveform signals and predefined waveform signals. The amplitude and frequency adjustments are made with the help of the computer, through the graphical interfaces, not requiring precision measuring devices.

Technical specifications:

  • Frequency range: 0.01 Hz - 1 MHz;
  • Stability provided by a quartz crystal;
  • Optical isolation from the computer;
  • Wave generated with low distortion;
  • TTL compatible outputs;
  • Storage of up to 32Kb waveform points;
  • Standard waveforms: sinusoidal, rectangular and triangular;
  • Library of predefined waveforms: noise, scan, etc .;

2. Electronic components for SMT technology

Surface mount technology or SMT (SMT = Surface Mount Technology, in English) has established itself in recent years as the main method of manufacturing electronic modules.

The surface mounting technology has allowed the realization of more efficient and reliable electronic modules, with a lower weight, volume and costs than the previous technology, which uses components with terminals for insertion. THT (THT = Through-Hole Technology).

The electronic components used have received names corresponding to these technologies, so we find components for surface mounting (SMD = Surface Mounted Devices, in English) and components with insertion terminals that we will further call THT components.

The idea of ​​mounting components on the surface is not new. The first SMD components, the so-called "flat packs" or flat capsules, in a rough translation, were used in hybrid circuits in the 1960s.

3. LDO Stabilizers - Low Drop-Out Voltage Regulators

Linear voltage stabilizers are very common today, especially when it comes to small monolithic fixed voltage stabilizers; the low cost makes them unbeatable.

However, when a lower input voltage is required or in order to have as much energy as possible from the batteries or accumulators used for portable equipment, some more expensive but more efficient integrated circuits must be used - low-drop stabilizers. input - output voltage or stabilizers LDO (from the Low Drop-Out Voltage Regulators).

For starters, only fixed, positive voltage LDO stabilizers will be addressed, although there are also adjustable or negative voltage LDO stabilizers.

4. Programming LCD (III) alphanumeric displays

This article comes as a result of the article "Programming LCD Alphanumeric Displays" in Conex Club Magazine issues 9-10/2002 si 11/2002.

In this article it is presented an application written in Turbo C to control the alphanumeric LCD display connected to the parallel port of the PC. The connection diagram was presented in the previous article.

5. TDA1562Q - 70W H-class audio amplifier

High power amplifiers, which can equip vehicles, are appreciated by many music audition enthusiasts.

As this interest is materialized by a growing demand, the companies specialized in the elaboration of the dedicated components have designed and offered to the market circuits for the realization of these amplifiers.

Thus, the prestigious Philips company produces the integrated circuit TDA1562Q which is able to develop an audio frequency power of 70W on a 4 Ohm load, if powered by 14.4V.

The peculiarity consists in the fact that the power supply is made from the battery, not requiring intermediate voltage-lifting elements.

The TDA1562Q circuit is a monotonic audio amplifier, class H, with deck exit stages (BTL) and 17-pin multiwatt capsule. At low output power, up to 18W, the circuit works like a normal BTL amplifier.

6. 13.8V / 20A switching source

The project was carried out in several stages and underwent repeated improvements. Various constructive solutions were tested, types of transistors and cooling systems, elements for eliminating disturbances and their source and, last but not least, magnetic elements and materials.

The idea he started from was the need to build a small, reliable and durable power supply to provide the energy needed to operate a professional 2m band transceiver.

Subsequent out-of-laboratory tests (by Y09HCE, Y09HCD) fully confirmed the initially proposed results. Fears that a switching source is noisier than a linear one have been contradicted by a professional transceiver. ICOM 737 working in full power SSB.

The performances measured on the prototype were the following:

  • Adjustable output voltage: 7… 14 Vdc;
  • Maximum current flow: 15… 20A for 13.8Vdc;
  • Adjustable output limit current: 4… 20A;
  • Maximum load stabilization: 0,1% (maximum 10mV drop for 13.8V @ 15A);
  • Maximum load efficiency: 85%;
  • Output ripple @ 35KHz maximum 50mVw;
  • Radiator temperature at maximum load, slightly ventilated: 48C;
  • Total weight 1,6 Kg.
  • The source is built with galvanic insulation, between primary and secondary, which gives extra safety in operation.

7. Pony Prog - Programmer PIC16C (F) 84

The application in figure 1 (from the article) is simple and quick to build. As specified in the previous issue of the magazine, this adapter can be attached to the interface presented, resulting in a useful and inexpensive programmer. PIC16C84 is the most used microcontroller in the series produced by Microchip.

The adapter uses few active components: three transistors (type BC557 and BC547) and a Zener diode (for 13V). For the microcontroller, a suitable 18-pin socket is used. Attaching the adapter to the interface is done through a 10-pin bar.

Note the existence of a selection jumper for choosing external voltage from a battery or directly from the interface. External voltage is required because PIC16C84 requires a high programming voltage of 12V (on the MCLR pin).

8. LCD display with programmable messages

It presents a module with LCD display, for programmable messages, with serial interface and eight inputs, made by Velleman, in the form of a kit.

Placing it in a low-level application will turn that application into a high-level application.

The K8045 kit, made by Velleman, makes it possible display user-created messages on an LCD screen. The selection of a message is done through 8 data entries, on two priority levels.

Message scheduling is done through a PC, the connection with it being made through an RS232 interface. The software offered by Velleman facilitates the introduction of messages. The LCD display is lit.

Technical specifications:

  • the lighting of the LCD display is done with a maximum number of 9 miniature bulbs, placed behind it;
  • the messages are displayed by simply pressing a button;
  • input commands can be made with simple contacts, logic integrated circuits or open-collector circuits;
  • programming is easy, through an attractive graphical interface, not requiring knowledge of any programming language;
  • can store (in a non-volatile memory) up to 9 messages of 16 characters each;
  • 4 operating modes are possible.


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