Conex Club Magazine - no.9 - 2004

Conex Club Magazine - no.9 - 2004 - Optotriace - Functioning, characteristics and applications

Reading time: 4 minute

The main topics presented

1. Optotriace - Functioning, features and applications

Optotriacs are fairly common electronic components today, although some electronics may not have worked with them yet.

They are intended, first of all, for this article, but also for those who have used optotriac in their assemblies, for a better acquaintance with them.

In the stores specialized in electronic components you can find a wide range of optotriace, at very affordable prices.

Optotriacs obviously belong to the family of optocouplers, being practically eight optocouplers with triac output. In fact, in French they are also named in catalogs "Optocouplers with triac output".

He have the role of achieving a very good galvanic insulation (of the order of 7500V) between the control circuit and the load.

Optotriacs are, in fact, optocouplers for the purpose of creating an interface between a low voltage logic control (a TTL gate, for example) and a load supplied at mains voltage.

Optotriacs are intended, with a predilection for ordering triacs, in order to achieve, for example, high power high voltage relays.

2. Double layer printed circuits - Made with Press-n'Peel foil

In many cases, the electronic modules presented in magazines or on various Internet pages, have the wiring made in two layers (it is also said that the primary laminate from which the wiring will be made is double plated).

Reproduction of such an application becomes difficult, there are several solutions to approach: redesign of printed wiring in the single layer version (which consumes a lot of time and requires design experience), execution of the original wiring with only a secure face (usually "bottom" or the one with several copper paths), the other to be made using electrical conductor (in the form of straps), etc.

The great difficulty in approaching the realization of a double printed circuit is achieving the correct alignment of the two corresponding drawings: the "top" and "bottom" faces.

You can imagine various solutions, but one of them offers perhaps the simplest: the execution of double-layer wiring with foil Press-n'Peel (PnP) Blue.

Why? The Blue foil (compared to the white one) offers a high degree of transparency, the alignment being made easier, after the holes corresponding to the forests.

There is only one unknown to be solved: the metallized holes, in order to prevent the tinning of the component pins on both sides of the wiring.

3. Temperature transducers (II) - Resistive transducers

Based on the principle of changing the resistance of a pure metal under the influence of temperature, thermoresistors are characterized by a positive temperature coefficient.

The most used material is platinum (Pt) but they are also thermal resistors based on nickel or copper.

The thermal resistors offer a high precision, linearity, a good stability in time and a wide range of working temperatures.

Among the disadvantages, we mention: cost, long response time and low sensitivity. Moreover, because they are often supplied with current, they are prone to precision degradation by self-heating, if this current exceeds 0,5… 1mA, but this shortcoming can be avoided with modern schemes and components.

4. Inflatable onset (I)

Two applications of great interest and practical utility are presented: IR switch and retranslator for remote control.

IR switch

Controls and remote controls that work in the infrared spectrum are widely used in many applications.

It is enough to remember how to control televisions, videocassettes or other household appliances and we have the impressive proportion of applications of this mode that uses as information carriers electromagnetic waves with wavelengths between 850nm and 950nm.

This electromagnetic spectrum is located in the invisible area, ie in the area where the eye does not perceive this radiation.

The described switch uses a single channel of the closed / open type (on / off), sensitive to IR radiation of a remote control transmitter modulated with a signal of 36… 38kHz.

The signals in the 36… 38kHz range are not detected by the human ear as ultrasound, but they are not detected by radio receivers either.

As most remote controls have many control buttons, we mention that the installation shown works when you press any button.

When a signal is emitted, the button must be held down for at least 1,5 seconds, the time required to overcome the delay given by R3 and C2. After this period, the relay receives a signal and remains triggered.

IR retranslator - Remote control extension

The remote controls that act in the invisible area of ​​the human eye, have the radiations located in the range with the wavelengths between 850 and 950nm.

The remote controls use a series of pulses in a very large combination which, properly decoded, they lead to the performance of the drive we want.

A receiving photodiode is sensitive to a much wider radiation spectrum than the emitted spectrum, generally between 400 and 1100nm.

This retransmitter can be set up in the idea of ​​controlling a device that is in another room where the remote control has no visibility, knowing that the propagation of IR waves is subject to the laws of optical radiation propagation.

For this purpose, the IR receiver circuit, SFH2030 it is mounted in a place where it can receive signals from the transmitter, and the LED which is a transmitting diode, in a place from which it can transmit signals to the device to be operated.

5. IR barrier

There is a barrier with infrared rays for various automation applications (automatic door opening, object counting, etc.) or in security systems. The assembly is based on integrated circuits LM358 and CD4011.

6. Development mode with uC PIC16F676

There is a development board for applications in the field of data acquisition, temperature measurement on 1-wire bus, digital interface, etc.

Under the name SmAll-smart A676 the assembly is part of a family of cheap and robust development modules, being intended for learning the programming of PIC microcontrols.

It is suitable for school electronics laboratories, but also for serious applications such as:

  • simulators and psychological testing systems;
  • data acquisition;
  • temperature monitoring;
  • dongle software protection systems on serial interface, etc.

The SmAll-smart A676 has a microcontroller PIC16F6761 / P operating in the extended temperature mode required especially for industrial applications.

With 1 program memory coke, 64 bytes of SRAM memory, 128 bytes of EEPROM memory, an 8-bit timer, a 16-bit timer, 4 unipolar analog measuring channels, 2 reconfigurable bipolar analog measuring channels, 8 digital inputs, a bus on a wire (temperature measurement, unique 64-bit code, etc.) , ICSP circuit reprogramming facility, RS232 communication, the module can be used in 101 different applications using a simple PC or terminal, for power supply, display and data acquisition.

7. Car alarm with self-arming

It presents an application made with discrete components, with multiple functions and a special feature: self-arming when leaving the car.

Proposed scheme controls, by means of switches, the condition of the doors, the trunk and the bonnet.

The switches used may be those already existing on the car to turn on the light in the passenger compartment or trunk (or additional ones can be mounted).

The alarm detects the opening of the contacts connected to ground. Two inputs are available, one timed, on which the front door switches are connected, thus allowing the vehicle to deactivate the alarm and an instant action input, which triggers the optical and acoustic warning immediately when opening the rear doors, trunk or hood engine.

Three outputs are available: one for the buzzer, preferably other than the car horn, and two for the position lamps, on the left and on the right, respectively.


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