We use many different types of communication in control applications to control home appliances, industrial appliances, and other type of automation. There are two types of communication that is we generally use - one is wired and other one is wireless. In wireless communication we transmits signal wirelessly, like using radio frequency (RF) and in wired communication in which we uses wires like copper wire. In this project “DTMF Based Home Automation System” we are going to control our home appliances wirelessly. Other important feature of this project is, that we are not going to use any microcontroller in it.
- MT8870 DTMF Decoder -1
- ULN2003 -1
- Relay 5 volt -3
- Bulb with holder or LED -3
- Connecting wires
- Bread board -2
- Aux Wire -1
- 9 volt battery -2
- PVT or Terminal Block -4
- 100K Resistor -2
- 330K resistor -1
- 0.1 uf Cap -2
- 22 pF cap -2
- 3.57 Mhz Crystal -1
- Mobile phone
- LEDs -3
- 1K resistor -6
- 7805 -1
Circuit Concept and Working
DTMF controlled home appliances project works over mobile DTMF technology that exists in Dial tone. DTMF stands for Dual Tone Multiple Frequency. There are some frequencies that we used to create DTMF tone. In simple words by adding or mixing two or more frequencies generates DTMF tone (Also check: DTMF Based Robot using Arduino). These frequencies are given below:
In Given figure we can see two groups of different frequencies. When one upper and one lower frequencies mixed then a tone is created that tone we calls Dual Tone Multiple Frequency. In this project we control ac appliances by pressing dial pad keys like 1, 2, 3, 4, 5 and more.
Here we have connected a cell phone using aux wire to the DTMF decoder circuit. Before explaining the further working of project we need to know about the output of DTMF decoder for every key pressed.
Now understand working according to given table.
In circuit diagram at Q1 LIGHT is connected, at Q2 FAN is connected and at Q3 TV is connected through relay driver IC. We have left Q4. Now when we press key 1 at the dial pad of mobile phone DTMF decodes this tone and generates a digital output given in table. Now According to given output in table Q1 is HIGH and Q1 is connected with light so LIGHT turned ON. If we want turned OFF the LIGHT, we need to press key number 8. Because in the output of key8, Q1, Q2 and Q3 LOW and Q4 are HIGH and we have not used Q4. So it doesn’t matter that Q4 is HIGH or LOW. But our operation has been performed because Q1 is LOW in key 8’s output and rest of appliances not affected. Now is we want to turned on FAN so we need to press key2 because by pressing key2 only Q2 is activated and rest of output are remain same. Now if we to OFF the FAN then we need to press key8 again like before for as LIGHT. Now if we want to TV so we need to press key4 and for tuning it OFF we need to press 8 like before. Now suppose we want to turned ON all of the appliances so we need to press key7 (see table) and for turning OFF all key8 (see table).
Now if we need to ON LIGHT and FAN so we need to press key3 (see table). And now we want to ON TV so we need to press key 7 not key4. Because we should keep remain turn ON previous appliances. Now if we want to turn OFF only LIGHT so we need to press key6. Because we should again to keep remain turn ON the previous appliances except LIGHT.
So we can control each of the appliances according to table output.
Circuit Diagram and Explanation
Circuit diagram for DTMF controlled home automation project is shown above. In this circuit we have used a DTMF decoder namely MT8890 IC which converts dial pad tone into the four bit digital output. LIGHT, FAN and TV are connected to Q1,Q2 and Q3 of DTMF decoder IC through a relay driver namely ULN2003. 5 volt SPDT 3 relays are used for controlling LIGHT, FAN and TV.
For demonstration of this project we have connected three LEDs at relay instead AC appliances. And we have also used 9 volt dc battery instead 220VAC for driving LEDs.