I’ll show you how to make a basic circuit named Mobile Controlled Home Appliances without Microcontroller in this project. That’s correct. You can control your household appliances without a microprocessor or programming using this circuit.
Outline
- Introduction
- Mobile Controlled Home Appliances Circuit Principle
- Cellphone Controlled Home Appliances Circuit Diagram without Microcontroller
- Circuit Components
- Mobile Phone Controlled Home Automation System Design without Microcontroller
- Working
- How to Operate DTMF Controlled Home Automation System without Microcontroller?
- DTMF Mobile Controlled Home Appliances Circuit Applications
- Circuit Advantages
- Circuit Limitations
Introduction
Unfortunately, we sometimes forget to turn off equipment such as fans and lights when we step outside, and we pay the price as a result. This article will show you how to create a simple circuit that will turn on the devices remotely and turn them off after the appropriate time interval to tackle these types of difficulties.
We’ve seen a lot of home automation projects that allow us to operate gadgets or appliances from afar, but the key advantage of this circuit is that it doesn’t utilise a microcontroller and instead employs components that are readily available in the market. In a previous piece, we looked at how a DTMF-controlled home automation system circuit works with a microcontroller.
Mobile Controlled Home Appliances Circuit Principle
DTMF communication is the basic principle used in this circuit. The abbreviation DTMF stands for Dual-Tone Multi-Frequency. When you call customer service, they will ask you to press the numbers to get the services you require. When you consider how they recognise the pressed number, DTMF enters the picture.
When you push the button on your phone, a tone with two frequencies is produced. The row and column frequencies of that particular button are represented by these two tones. If you click button 1, for example, a tone with a frequency of 697 Hz and 1209 Hz is generated. A DTMF keypad’s row and column frequencies are shown in the table below.
At the switching centre, these generated tones are processed to detect which button has been pressed. We must now employ these DTMF tones to control gadgets from a distance. A DTMF decoder is required to decode these DTMF tones at the receiver. These tones are converted into digital form by the Decoder IC. If you push the number ‘5′ on your mobile phone, the DTMF decoder will output ‘0101′.
Cellphone Controlled Home Appliances Circuit Diagram without Microcontroller
Circuit Components
- MT8870 DTMF decoder
- 5V relay Module
- 230V, 50 Hz AC motor (optional)
- BC547 Transistor
- 3.579545 MHz crystal
- 3.5mm audio jack
- LED
- 1N4007 Diode
- 0.1uF Ceramic capacitors – 2
- 20pF Ceramic Capacitors – 2
- Resistors (1/4 watt) – 1KΩ, 100KΩ x 2, 300KΩ
- Connecting wires
- Bread board
Mobile Phone Controlled Home Automation System Design without Microcontroller
It is preferable to use dedicated modules for the DTMF Decoder and relay rather than constructing them from scratch. If you’re utilising modules, you’ll only need to make a few tiny connections with jumper wires because all of the components are already in place.
Connect the receiver mobile phone and the DTMF Receiver board with an audio wire in the 3.5mm audio jack. The D0 pin (usually labelled Q1) is connected to the relay module’s input.
Working
The MT8870 DTMF decoder is the circuit’s essential component (a variant called CM8870 IC is used here). When you place a call to a linked mobile phone, the MT8870 IC sends a high pulse to the 15th pin after receiving a valid signal. When you push 1 on your phone, the decoder IC’s output at pins Q1, Q2, Q3, and Q4 will be 1, 0, 0 and 0 correspondingly.
Because the Q1 pin is linked to the relay’s input, it will be engaged, causing the load to turn on. To turn the load off, press any number that equals 0 in Q1, such as 2.
The following tables shows the Binary outputs corresponding to the buttons pressed on the mobile phone.
How to Operate DTMF Controlled Home Automation System without Microcontroller?
- Connect the wires according to the circuit schematic.
- Make sure there are no common connections between the AC and DC supply while making the connections.
- Keep the receiver mobile in auto answer mode by connecting the audio jack to it.
- The receiver phone’s profile should be set to general, and the keypad tones should be set to sound.
- Make a call to the receiver’s phone, which will automatically pick up the call because it is in auto answer mode.
- When the call is answered, dial number one on your phone. The relay will be activated as a result of this.
- Press 2 to turn off the relay.
DTMF Mobile Controlled Home Appliances Circuit Applications
- It’s used to regulate the appliances in the house.
- We can use this technology to control the robot.
- This circuit is used to set the on time for the water tank motor.
Circuit Advantages
- We can avoid the wastage of power
- We can control the devices from long distances also
Circuit Limitations
- No security is given, and anyone can manage the system simply dialling the receiver’s phone number.
- The number of devices that can be connected to the circuit is restricted.
