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We can use the unconventional remote control technology for controlling the home appliances easily without the fixed wall switch boards. Here I am using remote control technology (IR remote technology) and Bluetooth control technology using different wireless communication systems. We discuss about a few real time embedded systems based projects with which we can design and implement remote control circuit for home appliances.

Here, my target is to control AC devices other than DC devices, because in real time scenario we should handle AC machines/devices(High-Voltage). Mostly DC devices are for prototyping and small scale uses. So, in industry AC devices are common in manufacturing/maintenance works. Ex, mechanics, hydraulics, pneumatic, robotics, PLC, automatons and High-Voltage Zone and many more areas are present for real-time implementations of it.

Step 1: Infra Red Technologies

About Infra Red Technologies I have given in my last project(Infrared controlled RoboCar using Atmega32mcu).

It is not a very new concept, but the thing is that my explanation and experience that will help you learn and go in depth of technology. But, this is the project based on IR, but I am trying to control high-voltate(AC) appliances(eg., fan,bulb,motor etc). My goal is control machines which are used in our daily life in home, workshops, schools, colleges, offices, hospitals, factories and many more fields other than controlling dc(low voltage) appliances.

I am sharing some important concepts and figures related to this project. I wish some body will get some idea from it.

Keywords: Optical coupling, photo-conduction, electrical isolation, Triac, InfraRed, microcontrollers.

Step 2: Solid State Relay or Optocouplers or Digital Isolators

Both Photocouplers and Optical-coupled MOSFETs(OCMOS FETs) transmit signals while remaining electrically isolated.
Therefore, there may be some people who worry about difference of them. Then, we would like to describe their differences below:

  • Structural differences
  • Characteristic differences
  • Application differences

1. Structural differences
The figures(structure.gif) below show the principal internal structures of a photocoupler and an OCMOS FET.

As shown in the photocoupler on the left, when the light emitting diode (LED) lights up the phototransistor, the light generates a photocurrent that flows from the collector to the base of the phototransistor.
Accordingly, when the LED does not light up, the phototransistor is cutting off, and when the LED lights strongly, a large photocurrent flows from the collector to the base and the phototransistor is turned on steadily. Unlike when the base-collector is simply short-circuited, even if the collector-emitter voltage is less than the base-emitter forward voltage of a transistor, the photocurrent still flows and the phototransistor is conductive. On the other hand, as shown in the figure on the right above, the OCMOS FET incorporates photovoltaic cells, and when the LED lights up, the photovoltaic cells charge the gate capacitance to increase the gate-source voltage, turning on the MOS FETs in the case of a make-type contact. For a break-type contact, the FETs are conductive with no gate-source voltage. However, when the LED is lit, the photovoltaic cells bias the gate-source voltage reversely, cutting off the FETs. When the make-type OCMOS FET is turned off, the photovoltaic cells not only stop charging but the internal discharger switch is automatically closed, forcing the gates to discharge. As a result, the gate-source voltage immediately drops. Two FETs in an OCMOS FET are serially connected in reverse together. Therefore, when the OCMOS FET is conductive, both of the FETs conduct bidirectionally. However, when the OCMOS FET is not conductive, only the FET which is forward direction with the applied voltage cut off, while a parasitic diode of the another FET conducts.

2. Characteristic differences
Because of these structural differences above, photocouplers and OCMOS FETs have the characteristic differences as follows: Although photocouplers conduct only DC(direct current) in the output, OCMOS FETs can conduct both DC and AC (alternating current) in the FETs.Generally, the operating speed of photocouplers is microseconds or more rapid, while that of OCMOS FETs is as slow as milliseconds.Although the output conduction characteristics of the photocoupler vary depending on the input current value, those of the OCMOS FET are unrelated to the input current value.Generally and theoretically the photocoupler becomes conductive corresponding to an input. However, there are two kinds of OCMOS FETs: one kind that conducts (a-contact: Make-type contact) and one kind that breaks (b-contact: Break-type contact), when input is applied.Therefore, although high-speed operation like a photocoupler cannot be expected for OCMOS FETs, OCMOS FETs can switch AC and also a large current in the ampere range with a small input current (as small as a few milliampere).

3. Application differences

In general the photocoupler is used only for the transmission of a DC signal. Its applications include:
Pulse transmission (pulse.gif):

Analog DC signal transmission (analog.gif)

On the other hand, because an OCMOS FET's operating speed is slower than that of a photocoupler, it is rarely used for signal transmission.
However, because of the MOSFET's bidirectional conduction and low on-resistance features, it is mainly used as an "electronic switch" that intermits AC signals. Therefore OCMOS FETs are also called an SSR (Solid State Relay).

Step 3: Optoisolator (optical Coupler or Optocoupler)

An optoisolator (also known as optical coupler, optocoupler and opto-isolator) is a semiconductordevice that uses a short optical transmission path to transfer an electrical signal between circuits or elements of a circuit, while keeping them electrically isolated from each other. These components are used in a wide variety of communications, control and monitoring systems that use light to prevent electrical high voltage from affecting a lower power system receiving a signal.

In its simplest form, an optoisolator consists of a light-emitting diode (LED), IRED (infrared-emitting diode) orlaser diode for signal transmission and a photosensor(or phototransistor) for signal reception. Using an optocoupler, when an electrical current is applied to the LED, infrared light is produced and passes through the material inside the optoisolator. The beam travels across a transparent gap and is picked up by the receiver, which converts the modulated light or IR back into an electrical signal. In the absence of light, the input and output circuits are electrically isolated from each other.
Electronic equipment, as well as signal and power transmission lines, are subject to voltage surges from radio frequency transmissions, lightning strikes and spikes in the power supply. To avoid disruptions, optoisolators offer a safe interface between high-voltage components and low-voltage devices.

An optoisolator (also known as optical coupler, optocoupler and opto-isolator) is a semiconductordevice that uses a short optical transmission path to transfer an electrical signal between circuits or elements of a circuit, while keeping them electrically isolated from each other. These components are used in a wide variety of communications, control and monitoring systems that use light to prevent electrical high voltage from affecting a lower power system receiving a signal.
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In its simplest form, an optoisolator consists of a light-emitting diode (LED), IRED (infrared-emitting diode) orlaser diode for signal transmission and a photosensor(or phototransistor) for signal reception. Using an optocoupler, when an electrical current is applied to the LED, infrared light is produced and passes through the material inside the optoisolator. The beam travels across a transparent gap and is picked up by the receiver, which converts the modulated light or IR back into an electrical signal. In the absence of light, the input and output circuits are electrically isolated from each other. Electronic equipment, as well as signal and power transmission lines, are subject to voltage surges from radio frequency transmissions, lightning strikes and spikes in the power supply. To avoid disruptions, optoisolators offer a safe interface between high-voltage components and low-voltage devices.

The optoisolator is enclosed in a single device, and has the appearance of an integrated circuit (IC) or a transistor with extra leads. Optocouplers can be used to isolate low-power circuits from higher power circuits and to remove electrical noise from signals. Optoisolators are most suited to digital signals but can also be used to transfer analog signals. The isolation of any data rate of more than 1 Mb/sec is considered high speed. The most common speed available for digital and analog optoisolators is 1 Mb/sec, although 10 Mb/sec and 15 Mb/sec digital speeds are also available. Optoisolators are considered too slow for many modern digital uses, but researchers have created alternatives since the 1990s.

In communications, high-speed optoisolators are used in power supplies for servers and telecom applications -- Power over Ethernet (PoE) technology for wired Ethernet LANs, for example. Optoisolator components can also protect Ethernet and fiber optic cables from electrical surges. InVoIP phones, electrical signals can be isolated using a transistor output optocoupler.

Although no longer common, where modems are used to connect to telephone lines, the use of optoisolators allow a computer to be connected to a telephone line without risk of damage from electrical surges or spikes. In this case, two optoisolators are employed in the analog section of the device: one for upstream signals and the other for downstream signals. If a surge occurs on the telephone line, the computer will be unaffected because the optical gap does not conduct electric current.

Step 4: Switching High Current Loads Using a Triac

TRIAC, from triode for alternating current, is a genericized tradename for an electronic component that can conduct current in either direction when it is triggered (turned on), and is formally called a bidirectional triode thyristor or bilateral triode thyristor.

Wiki-link: "https://en.wikipedia.org/wiki/TRIAC"

TRIACs are a subset of thyristors and are closely related to silicon controlled rectifiers (SCR). However, unlike SCRs, which are unidirectional devices (that is, they can conduct current only in one direction), TRIACs are bidirectional and so allow current in either direction. Another difference from SCRs is that TRIAC current can be enabled by either a positive or negative current applied to its gate electrode, whereas SCRs can be triggered only by positive current into the gate. To create a triggering current, a positive or negative voltage has to be applied to the gate with respect to the MT1 terminal (otherwise known as A1).

Once triggered, the device continues to conduct until the current drops below a certain threshold called the holding current. The bidirectionality makes TRIACs very convenient switches for alternating-current(AC) circuits, also allowing them to control very large power flows with milliampere-scale gate currents. In addition, applying a trigger pulse at a controlled phase angle in an AC cycle allows control of the percentage of current that flows through the TRIAC to the load (phase control), which is commonly used, for example, in controlling the speed of low-power induction motors, in dimming lamps, and in controlling AC heating resistors.

Applications:
Typical use as a dimmer.....

Low-power TRIACs are used in many applications such as light dimmers, speed controls for electric fans,bulbs and other electric motors, and in the modern computerized control circuits of many household small and major appliances.

Step 5: Main Steps and Components for This Project:

The main steps:

  1. The seven segment display used to show the current speed level.
  2. The TSOP1738 sensor for remote control.
  3. OUT – Here the AC load is connected in series.( 220v)AC Bulb/Fan
  4. IN – Power supply from 6v dc.
  5. MCU – ATmega32 AVR 8 bit Microcontroller.

Components are:

  1. 330 ohm resistor (9 Nos)
  2. 4k7 Resistor (2 Nos)
  3. 1K/2 watt Resistor
  4. 15/5 watt ohm Resistor
  5. 1K5 Resistor
  6. 22pF Ceramic Disk Capacitor (2 Nos)
  7. 0.1uF Ceramic Disk Capacitor 250V(1 Nos)
  8. 0.1uF Ceramic Disk Capacitor (2 Nos)
  9. 470uF 50v Electrolytic Capacitor
  10. 1N4007 Diode (6 No)
  11. LED 5mm Any Colour
  12. MCT2E Opto Coupler
  13. Triac BT136U3(1)
  14. Common Anode DisplayDISP11
  15. TSOP1738 IR Sensor(1)
  16. ATmega32 AVR 8 bit Microcontroller- board

Step 6: Circuit Diagram

Connect as the diagram given above or you can change as your need.

Step 7: Codes

This is KSETindia development board and lcd library is already given. So, I am calling functions given in library for display in lcd screen.......

//Program ####################################

#include "avr/io.h"
#include "lcd_io.h"

void display(int);

void disp(int);

int main()

{

uint8_t cmd; //Command received from remote

Initialize();

lcd_init();

while(1)

{

//Get Command For the Remote Control

cmd=GetRemoteCmd(1);

display(cmd); //Now process the command //UP Key

if(cmd==31)

{

if(speed<9) speed++;

disp(speed);

}

//DOWN Key

if(cmd==27)

{

if(speed>0) speed--;

disp(speed);

}

//Enter Key

if(cmd==26)

{

if(fan_on)

{

POWER_LED_OFF();

fan_on=0; //Turn Off

}

else {

POWER_LED_ON();

fan_on=1; //Turn On

}

}

Display(speed);

}

return 0;

}

display(int ch,int sp)

{

lcd_clrscr();

lcd_gotoxy(0,0);

//lcd_putc(ch);

lcd_puts("IR Decoder: ");

lcd_putc(' ');

lcd_puti(ch,0);

}

disp(int sp) {

lcd_clrscr();

lcd_gotoxy(0,0);

lcd_puts("Speed: ");

lcd_putc(' ');

lcd_puti(sp,0);

}

<p>Thanks for your response, Sure I'll keep in mind your advice.</p>

About This Instructable

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Bio: Rudra Narayan Paul. . . . . . . ., M.TECH (CSE), . . . . . . . . . . . . . BPUT, ODISHA, INDIA. . . . . . Facebook-ID: Rudra Narayan. . More »
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