How often have you walked out of your room and forgotten to turn OFF your light bulb? And it is frustrating to enter again just to switch OFF the lights. Your days of frustration are now over, as we bring you an easy solution to turn the electric devices in your home OFF or ON, using a simple remote. In the era of home automation, even the most routine tasks can be transformed into effortless experiences. Yes, Remote-operated bulbs are available in the market but, do you need to buy one, when you can easily build a remote-operated bulb by yourself? Thinking about how you can build it?

Do not worry, we are here to help you out. This article explores the convenience and practicality of bulb control using a remote, empowering homeowners to effortlessly switch lights on or off. So, let’s dive into it!


Required Components


RF Home Automation Circuit Diagram

RF Home Automation Circuit Diagram


Why have we used RF devices instead of IR devices?

You might be thinking, can I not make an automation system using a device that uses IR instead of RF? Well, you can use an IR transmitter and receiver, but it comes with many limitations that can be easily overcome by an RF transmitter-receiver circuit.

The major drawback of the IR system is its short range (10m) which is much shorter than the range of the RF system (100m), which provides long distance and easier control to the user.

Secondly, it is difficult for IR to penetrate opaque surfaces which means it cannot function if any obstacle is present between the transmitter and receiver. This does not apply to the RF devices, it can easily function even if there are obstacles present, as long as the transmitter is within the range of the receiver.

433 MHz RF Transmitter Remote Control

433 MHz RF Transmitter Remote Control


    What is a 433 MHz Radio Frequency Transmitter Remote? As the name suggests, a 433 MHz Radio Frequency (RF) transmitter remote is a remote-control device that transmits radio frequencies at 433 MHz. These remote controls are used in a variety of applications, such as wireless doorbells, garage door openers, home automation systems, and even remote-controlled toys.

    The remote operates on a battery, the voltage requirement can vary depending on the remote being used. In this case, the remote requires a 3V battery to operate. It has two push buttons, which are used to control the operation of the bulb. The range of this transmitter is around 100m.

    The remote control device has a transmitter module that sends out radio frequency signals at a specific frequency of 433 MHz. This module includes a radio frequency oscillator, radio frequency modulation circuits, and an antenna to send out the signals.

    The remote also involves an encoding mechanism representing the buttons or functions being pressed. In this module, it is achieved by using an HT-12E encoder module. It is commonly used because of its low power consumption and high noise immunity. Several encoding mechanisms such as binary encoding can be used. Complex coding schemes like rolling code or fixed code are also used in many applications, like remote car keys etc.

     433 MHz RF 1 Channel Receiver Relay

    433 MHz RF 1 Channel Receiver Relay

    Before we dig into the working of the receiver module, let us see how the relay operates and what role it plays in working this circuit.

    So, what is a relay and why do we need it?

    Relays are switches that are controlled by electricity. A set of operating contact terminals and a set of input terminals for multiple control signals make up the device. These are used to control the flow of current in another circuit, without human intervention.

    A movable contact connected to switch contacts gets connected to the electromagnet when a low-power control signal is applied to the relay's coil. When the switch contacts are closed, the controlled circuit is complete and a larger current can flow. When the control signal is removed, the electromagnet de-energizes, causing the switch contacts to open and interrupting the current flow.

    • Negative Terminal: The Negative Terminal of the relay is connected to the negative of the DC supply from SMPS.
    • Positive Terminal: The Positive Terminal of the relay is connected to the Positive of the DC supply from SMPS.
    • NO (Normally Open): Its default state is Open Circuit. When the relay is turned on by applying power, its internal circuitry is activated, closing this contact (i.e., pushing the internal lever switch to the NO position) and allowing current to pass through it.
    • NC (Normally Closed): When the relay is deactivated, this contact will typically be closed (or on), and current will flow.
    • COM: Relays have a moving component called the COM (Common) connection. The NC (Normally Closed) is linked to the COMMON when the relay is off. Before the relay turns on, the NO (Normally Open) connection is not connected. The common switch switches from NC to NO when the relay is turned on.

    Learning Button: A learning button is present on the receiver module. This button can be used to change between the different modes provided by the circuit. The functioning of the button is explained below:

    No. of button presses

    Operating Mode


    Momentary Mode


    Latch Mode


    Toggle Mode




    Working of Receiver Circuit

    The flip side of a 433 MHz RF transmitter remote is a 433 MHz RF receiver. The 433 MHz RF receiver receives radio frequency signals delivered at 433 MHz through its antenna. The received signals are subsequently transmitted to an RF receiver module that is adjusted to operate at the same frequency.

    The operating voltage for the receiver module is 6V to 12V. Its range can vary depending on the module being used. The one we are using has a range of about 100m.

    The signals are amplified and demodulated by this module, which extracts the original data or information embedded within them. The decoding procedure translates the encoded instructions or data sent by the corresponding 433 MHz transmitter. The decoder module used in the receiver is an HT-12D, which is the counterpart of the HT-12E encoder.

    The decoded information is then sent to the output interface of the receiver module, which is a relay in this case. The output from the receiver module is used to control or trigger specific actions based on the received information. In our case, the decoded commands are used to control the switching of the light bulb.

    Switch Mode Power Supply Module (SMPS)

      Switch Mode Power Supply Module

      A Switched-Mode Power Supply (SMPS) module is an electronic device that efficiently converts electrical power from one form to another. It uses a diode bridge to rectify an input voltage, which can be either AC (alternating current) or DC (direct current), into DC. The rectified DC voltage is then filtered to remove any ripples or fluctuations, resulting in a smoother DC signal.

      A power switching device, frequently a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) operating in switching mode, converts the filtered DC voltage to high-frequency AC voltage.

      This switching procedure makes power conversion efficient. The module uses a feedback mechanism that constantly checks the output voltage or current to regulate the switching.

      The high-frequency AC voltage is then routed through a transformer. In addition to providing isolation between the input and output circuits for safety and noise reduction, the transformer steps up or down the voltage depending on the desired output. The high-frequency AC voltage is again converted into a regulated DC voltage with minimal ripple by rectifying and filtering the transformer's output. The power output is reliable and stable after this stage.

      The SMPS module includes a regulation mechanism that maintains a constant output voltage or current. This mechanism modifies the switching frequency or duty cycle of the power switching device by comparing the output voltage or current with a reference value. The regulated DC voltage or current is then made available at the SMPS module's output terminals to be used by systems or connected devices.

      The connections for the SMPS Module are demonstrated below:

      SMPS Module Connections

      Now that we are done with learning how the components work, and their importance in this home automation system, it is time to explore how the assembled system works.


      Working of the Home Automation System

      The receiver relay can operate in 3 modes that are toggle, latch and momentary. Here is a brief explanation of how they work:

      • Momentary Mode: Pressing the learning button once activates the device's Momentary mode, which is comparable to a doorbell's operation. The signal is only transmitted while the button or switch is being pressed, and it ceases as soon as it is released.
      • When the button on the remote is pressed by the user, the transmission is successfully initiated and the relay switches to an ON state. This state remains as long as the button is held down. However, when the user releases the button, the transmission ceases, and the relay returns to its original OFF state.
      • Toggle Mode: In this mode, when the user presses button A, the relay is turned on and remains in that state until button A is pressed again. In toggle mode, the same button is used to both turn the relay on and off. The relay directly controls the power that is transmitted to the bulb, so switching the relay on or off also switches the bulb on or off.
      • Latch Mode: The latch mode enables each button on the remote to perform a singular function, which is either turning the relay ON or OFF. For instance, if button A is used to turn ON the bulb or relay, then button B will have the sole responsibility of turning it OFF. This is different from the toggle mode, where button A can also turn OFF the bulb.
      RF based Home Automation

      The automation circuit operates simplistically. The SMPS module converts the AC voltage to the desired DC voltage, typically 12V, and supplies power to the connected relay. When the user presses a button on the transmitter remote, a 433MHz signal is transmitted to the receiver to execute the desired action. The receiver receives the signal and activates or deactivates the relay based on the button pressed.

      Let's understand this concept with an example. Suppose you have set the receiver module in Latch Mode and linked it to a bulb. Button A activates the bulb, while button B deactivates it. When you press A, a signal is transmitted to the receiver, activating the relay, and turning on the bulb. When you are done, pressing Button B sends a signal to the receiver, deactivating the relay and turning off the bulb.



      This is the completion of your design for a remote-operated bulb. The successful design includes a home automation system that utilizes a 433 MHz RF Remote and Receiver Relay. By incorporating multiple-channel relays, you can now control additional devices. The purpose of this project was to introduce controlling your devices through an RF remote and receiver module with the use of a single-channel relay.

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