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RF Remote Control Circuit for Home Appliances

Posted: 24 Jun 2014 04:18 AM PDT

We have already learned in earlier post about how design IR Remote Control for Home Appliances. But, have you ever tried to design wireless communication circuit without any microcontroller? This article explains you how to control the home appliances wirelessly using RF technology.

Here we have used RF434 MHz modules to make wireless remote. Using this remote, we can control the appliances within the range of 100 meters. This project has two sections, one is transmitter section and the other is receiver section. At transmitter section, we use HT12E encoder and at receiver section, we use HT12D decoder.

RF Remote Control Circuit Principle:

When we press any key in the remote, the transmitter section generates the corresponding RF signal and this signal is received by the receiver section, hence it switches the corresponding appliance.

A four channel encoder/decoder pair is used in this system. The input signals at the transmitter section are taken from the four switches and the output signals at the receiver are indicated by the four LED's corresponding to each switch.

RF Parellel to Parellel

RF Parellel to Parellel

Here, the encoder HT12E is used to convert parallel data to serial. This data is transmitted serially to receiver point through RF.

RF receiver receives the data serially and then gives to the HT12D decoder to convert it to the parallel. Four LEDs indicate the received data.

Circuit Diagram of RF Remote Control for Home Appliances without using Microcontroller:

Circuit Diagram of Remote Control Circuit Through RF Without Microcontroller

Circuit Diagram of Remote Control Circuit Through RF Without Microcontroller

Circuit Components:

  • HT12E encoder IC
  • HT12D decoder IC
  • RF 434 MHz transmitter and receiver
  • Resistors – 33k,750k
  • 220 ohm Resistors – 4
  • Push buttons – 4
  • SPST switch – 1
  • LEDs – 5 

RF Remote Control for Home Appliances without Microcontroller Circuit Design:

HT12E Encoder: This encoder IC is integrated 2^12 series of encoders. This IC is mainly used to interface RF and IR circuits. This IC converts 12 bit parallel to serial. These 12 bits are divided into 4 data bits and 8 address bits.

This IC has transmitter enable pin. When trigger signal is received on this pin, the address and data bits are transmitted together. HT12E starts a 4 word transmission cycle upon receipt of enable. The transmission cycle is repeated till transmitter enable is kept low.

HT12D Decoder: Thisdecoder IC converts serial input data to parallel. This IC indicates valid transmission by a high at VT (Valid Transmission) pin.

HT12D is capable to decode 12bit data (8 address bits and 4 data bits). The output data remains unchanged till the new data is received.

It is mainly used in RF and IR circuits. These decoders are mainly used for remote control applications like burglar alarm, car door alarm, security system etc.

The chosen pair of encoder and decoder for communication should have same number of address and data bits.

RF Modules (434MHz):

This module operates at radio frequency. The Radio frequency range is 30 KHz to 300 GHz. In this system, RF modules use ASK (Amplitude Shift Keying) modulation.

Transmission through RF is better than IR because, the RF signal can travel for longer distances as compare to infrared. And IR mostly supports line-of-sight mode, RF signals can travel even there is an obstruction. RF transmission is more reliable and stronger as compare to IR.

The chosen pair of RF Transmitter and receiver should have same frequency. The transmission speed of these modules is 1Kbps to 10Kbps.

RF Modules Pin Diagram

RF Modules Pin Diagram

How to Operate this RF Remote Control Circuit?

  1. Connect the circuit as shown in the diagram.
  2. Apply 5V supply to the transmitter and receiver sections. Now you can observe that all the LEDs at receiver will glow.
  3. Press the first button at transmitter section; you can observe that first LED will off at receiver section. In the same way when you press any button at transmitter section the corresponding LED at receiver will OFF.
  4.  Now disconnect the power supply from transmitter and receiver sections.

RF Remote Control Circuit Advantages:

  1. Works for longer distances as compared to IR.
  2. RF signals can travel even there is an obstruction between transmitter and receiver.

RF Remote Control Circuit Applications:

  • Used for remote control applications like burglar alarm, car door alarm, calling bell, security systems, etc.

Limitations of the Circuit:

  • The mode of communication is complex.
  • As we are using ICs, they consume more power.

The post RF Remote Control Circuit for Home Appliances appeared first on Electronics Hub.

Super Sensitive Intruder Alarm

Posted: 24 Jun 2014 01:32 AM PDT

This circuit is designed to alert the user when an intruder enters into the home. If there is any obstacle in front of IR sensor, it generates an interrupt signal. This interrupt signal is given to the speaker to alert the user.

Super Sensitive Intruder Alarm Circuit Principle:

IR transmitter always emits the IR (Infrared) rays which have to be received by IR receiver. When there is an obstacle in front of IR sensor, the transmitted IR rays are reflected back to the IR receiver. The output of Op-Amp is high when IR receiver receives the reflected IR rays. This output of operational amplifier is connected to the RESET pin of 555 timer.

Related Post: Security Alarm Circuit without using 555 Timer IC

The output of 555 timer is low when input voltage applied at pin 4 of 555 timer is low.

When input voltage at pin 4 is high, then 555 timer produces the frequency which can be adjusted by the different value combinations of resistors R1, R2 and capacitor C3.

  • Obstacle Present → IR Receiver Receives IR Rays → Op-amp Output High → 555 RST Pin High → Speaker Produces the Sound.
  • No Obstacle → IR Receiver does not Receive the Rays → Op-amp Output Low → RST Pin Low → No Sound

The output of NE555 is filtered by the 1uF capacitor and fed to the speaker.

Many IR sensors are arranged in house at different locations. The outputs of all these sensors are given to RESET pin of common 555 timer. When any sensor detects the intruder, the reset pin of 555 timer becomes high and speaker will produce the sound.

Super Sensitive Intruder Alarm Circuit Diagram:

Super Sensitive Intruder Alarm Circuit Diagram

Super Sensitive Intruder Alarm Circuit Diagram

Circuit Components:

  • NE555 timer
  • LM358 op-amp
  • Pot – 10k, 4.7k
  • IR transmitter
  • IR receiver
  • Red led
  • Ceramic capacitors – 0.1uF, 0.01uF
  • Electrolytic capacitor – 1uF, 16v
  • Resistors – 10k, 100, R4,R5
  • 2 resistors – 330 ohm
  • Speaker
  • Battery

Super Sensitive Intruder Alarm Circuit Design:

555 Timer: Here 555 timer acts as a free running oscillator. It will generate the frequency when high pulse is applied at RESET pin. The generated frequency of 555 timer varied by varying resistor values R4, R5 or by varying the capacitor value C3.

Here Pin 2 and pin 6 of 555 timer are shorted to allow the triggering after every timing cycle. In this circuit, capacitor C3 charges through the resistors R4, R5 and discharges through the resistor R5.

LM358 Op-Amp:

Op - Amp

LM358 Op-Amp

IF   V1>V2 then OP = HIGH

IF   V2>V1 then OP = LOW

LM358 IC consists of two operational amplifiers. Each Op- amp has two inputs (inverting and non – inverting) and one output. The op – amp output is high when non-inverting voltage is greater than the inverting voltage and it is low when inverting voltage is greater than non inverting voltage.

IR Transmitter: The operating voltage of transmitter is around 2 to 3V, to drop the remaining voltage we connect a resistor in series with IR led.

IR Receiver: It is always used in reverse bias. It almost acts as a closed circuit when it receives IR rays and it has high resistance when it does not receive any IR rays.

Also read the post – Motion Detector Circuit using NE555 Timer

How to Operate Super Sensitive Intruder Alarm Circuit?

  • Give the connections according to the circuit diagram.
  • Connect 5V supply to the circuit.
  • Now place the obstacle in front of IR sensor then speaker produces the sound.
  • Remove the obstacle now you will not get any sound.
  • Disconnect the battery from the circuit.

Super Sensitive Intruder Alarm Circuit Applications:

  • This circuit is used in homes and offices for security purpose.

Super Sensitive Intruder Alarm Circuit Limitations:

  • This circuit produces the sound even if there is any non-living thing in front of IR sensor.

The post Super Sensitive Intruder Alarm appeared first on Electronics Hub.

TV Remote Jammer Circuit

Posted: 23 Jun 2014 11:55 PM PDT

We have already seen in the earlier posts about how to jam the mobile signals using simple mobile jammer circuit. Now, In this post, we are going to know about another interesting concept i.e. TV Remote jammer circuit. It is designed using NE555 Timer IC.

This proposed TV jammer circuit confuses the infrared receiver in a TV by producing the constant signal that interferes the remote control signal. If you switch on the circuit once, the TV will not receive any command from the remote. This allows you to watch your own program without anyone changing the channel or volume.

The fundamental technology used in TV Remotes is Infrared light. This infrared light is invisible to the human eye, but we can see these IR rays through camera.

TV Remote Control Jammer Circuit Principle:

The idea behind TV remote control jammer is sending a constant IR pulse with the carrier frequency of the transmitter. Hence the result will be non-accepted signal from the receiver and therefore no action will be taken.

Basically the TV remote emits a sequence of pulses when you press a button. IR transmitter is fixed to the surface of the TV remote. This IR transmitter emits the pulses in unique configuration for each button.

IR receiver which is arranged to TV will receive these sequence of pulses that are transmitted by TV Remote and identifies which button is pressed in TV remote.

Generally Philips TV remotes follows RC5 (Remote Control) protocol. This protocol was developed by Philips in the late 1980s. According to this protocol, for each button, Remote transmits 14 bits. The below figure shows the frame format of RC5 protocol.

RC-5 Frame Format

RC-5 Frame Format

The first two pulses are start bits, and both are logic 1.

The 3rd bit is toggle bit. This bit toggled every time when a button is pressed or released. Using this bit, we can identify weather the button is pressed or not.

The next 5 bits represent the device address. Bit 4 is the MSB of the device address and bit 8 is the LSB of the device.

Last six bits in the frame format are command bits. These command bits varies for each button in the remote. Using these command bits, we can identify which button is pressed in IR remote.

Features of RC5 protocol:
  1. Bi-phase coding (Manchester coding)
  2. 36Khz or 38Khz carrier frequency
  3. Constant bit time of 1.778ms
  4. 5 bit address and 6 bit command length

Modulation: The RC5 protocol uses bi – phase modulation. All 14 bits are equal length of 1.778ms.

TV Remote Control Jammer Circuit Diagram:

Circuit Diagram of TV Remote Jammer using 555 Timer IC

Circuit Diagram of TV Remote Jammer using 555 Timer IC

Circuit Components:

  • NE555 timer
  • 1n4148 diodes -2
  • Resistors – 470 ohm, 1k, 5R6
  • Pot – 10k
  • 9V Battery
  • Ceramic capacitor – 10nF
  • Transistor – NPN
  • IR – LED

TV Remote Jammer Circuit Design:

The circuit is designed to produce a 38 KHz signal. The main component in this circuit is 555 Timer. Here, it is operated in astable multivibrator mode. In this circuit, 2nd and 6th pins are shorted to allow the triggering after every timing cycle and these two pins are grounded through the capacitor. 4th pin of 555 timer is connected to supply to avoid sudden resets.

10k pot is used to adjust the frequency of 555 timer. The current through the IR-LED is limited to 100mA because of two 1n4148 diodes, as these form constant current arrangement when combined with transistor and resistor.

Related Post: Also get an idea about how simple FM Radio Jammer Circuit Works!

How to Operate this TV Remote Control Jammer Circuit?

  • Connect 9v battery to the circuit.
  • Now adjust the pot 10k to produce 38 KHz signal.
  • Now press the TV remote buttons.
  • You can observe that TV will not receive any commands from remote
  • Disconnect the battery from circuit and press TV remote buttons.
  • Now you can observe that TV will receive the commands from Remote

TV Remote Control Jammer Circuit Advantages:

  1. We can use this circuit to jam the remote signals so that the other people cannot change the channel while watching our favorite program on TV.
  2. It will not affect the signal receiving capacity of the TV.

Limitations of the Circuit:

  • The circuit should be tuned correctly to 38 KHz frequency to get accurate results.

The post TV Remote Jammer Circuit appeared first on Electronics Hub.