Технические науки/ 6

Технические науки/ 6. Электротехника и радиоэлектроника

Ph.D. Iryna Zharikova, Oleksandr Botsman

Kharkov National University of Radio Electronics

Intelligent lighting control system

based on piezoelement

1. Introduction

At present time there is a requirement to automate routine actions made by man. Tasks of this sort are considered during "smart home" systems design.

One of the most important tasks during development of a number of similar projects is to create intelligent lighting control system. Such systems can be designed on the base of various sensors that detect sound vibrations and control the "smart house" lighting according to a predetermined algorithm using a microcontroller.

2. Task formulation

In this regard it was decided to develop a compact intelligent lighting control system, which should provide:

- switching on and off of network load during the detection of double-clapping;

- minimal false actuations;

- no need for additional power supply;

- small weight and size of the finished device in the packaging.

The structure of such a system includes:

- a microcontroller – for control all elements of the system;

- a sensor that will detect the acoustic waves;

- an universal electromagnetic relay – for switching on and off of network load;

- circuits of power supply formation from the mains voltage.

It is advisable to start the development of this device with the selection of the sensor. It must possess the following features:

- respond exclusively to sharp splashes of sound vibrations;

- have a resonant frequency close to the frequency of the sound of clapping hands.

3. A sensor selection on the basis of the research results analysis

To provide needed characteristics various types of sensors were investigated. These researches were based on a measurement of sensor sensitivity G and bandwidth depending on the frequency of sound vibrations f. For analysis convenience, the data are grouped and presented as a graph (Fig. 1).

$C:\Users\Botsman\Desktop\статья ас-1\C.tif$

Figure 1. The sensors sensitivity oscillogram

$C:\Users\Botsman\Desktop\статья ас-1\датчик.tif$

Figure 2. Piezosensor CBEG2240BP

Based on the research results analysis the required sensor was selected. It was piezosensor CBEG2240BP of Daeyoung firm (Fig. 2). It has the following parameters:

- input voltage – 9 V;

- sound pressure level – 90 dB;

- resonant frequency – 4000 Hz.

The use of piezoelectric transducer in the developed device will allow capturing only acoustic splashes with frequency close to the handclaps, and will ignore other – more uniform – oscillations of the sound spectrum.

4. The analysis of the developed system

The developed device is powered by 220 V and requires no additional power supply. It is connected in-sequence with the load as any electrical lighting equipment with power consumption to 1540 watts. Other technical characteristics of the device are presented in the Tab. 1.

Table 1

Device characteristics	Value
Nominal voltage, V	220
Sensor type	piezoelectric element
Work range, m	10
Maximum load current, A	7
Maximum load power, W	1540
Power consumption, W	not more 0.2

The schematic circuit diagram of the device is shown in Fig. 3. Electronic part power built on transformerless power supply [1] consisting of a quenching circuit C1, R1, where the voltage drops to 70 V. Then, using rectifier VDS1 a constant voltage is formed, which drops on the stabilizer diode VD1 to 12 V. This voltage is used to supply the relay K1 coil, and to supply the voltage regulator structurally made on the integrated circuit chip DD1. After stabilizer the constant voltage of 5 V powered microcontroller DD2 and one stage of amplification, made on bipolar transistor VT2. Signal source for the latest is sound pressure sensor built on the principle of piezoelectric effect. For a given algorithm when it is necessary to connect the load to the network of 220 V, the microcontroller sets a high logic level, which through resistor R2 closes transistor VT1 switch, thereby connecting the second end of the relay coil to the ground. This leads to the closure of the power contacts of the relay and to connection of load to the main network.

This device is controlled by a single-chip 8-bit FLASH CMOS microcontroller PIC12F683 of Technology Incorporated company [2]. In this case, the microcontroller used in the package SOIC8.

Figure 3. Electrical circuit diagram of lighting control device

The main functions of the microcontroller are:

- analysis of the analog input of the internal comparator CIN-;

- with a sufficient pulse amplitude – recording of this event;

- control of input pulses by time intervals;

- at violation of intervals – reset the session and return to the initial standby mode;

- at compliance with all requirements of the program logic – setting a high logic level in output pin GP5, which, in turn, closes the transistor switch VT1, thereby connect the load HL1 to 220 V.

Figure 4. The algorithm of the microcontroller program

The algorithm for microcontroller work is shown in Fig. 4.

The key points of this algorithm are "protected pauses" between the detection of the input low-frequency splashes. This solution ensures a correct load control and eliminates most false actuations [3].

To confirm the effectiveness of the chosen technical solution, a series of measurements were performed. Dependences of the sensitivity of the developed device from a source of sound splashes remoteness L, and the radiation pattern on the axis of the source of acoustic oscillations are shown in Fig. 6-7.

$C:\Users\Botsman\Desktop\статья ас-1\D1.tif$

Figure 6. Radiation pattern of device

$C:\Users\Botsman\Desktop\статья ас-1\F.tif$

Figure 7. Graph of the sensor sensitivity from the distance to it

Conclusions

Thus, in this paper a method of non-contact control of lighting was proposed. Intelligent system based on piezoelement allow remote switching on and off a variety of lighting equipment. The device has a narrow bandwidth tuned to the selective choice of clapping audio frequency. As can be seen from the radiation pattern (Fig. 6), the developed system catch sound vibrations even at distance of 10 meters from the sound source, which allows to place it in most living accommodations, without fear for the stability of actuations. That is, the tasks of research were carried out and implemented in the form of finished device.

References

[1] Антипенский Р.В., Фадин А.Г. Схемотехническое проектирование и моделирование радиоэлектронных устройств. М: Орион, 2007. 128 с.

[2] Предко М.А. Справочник по PIC-микроконтроллерам. М: ДМК Пресс, 2002. 324 с.

[3] Жарикова И.В., Боцман А.С. Интеллектуальная система управления освещением на базе пьезоэлемента. Радиотехника. №180. 2015. С. 102-105.