How to control house-hold gadgets with phone through DTMF decoder

How to control house-hold gadgets with phone  through DTMF decoder

Here we present the full automation with DTMF. Here you can use your phone to control all the house appliance. This particular project I designed it for Hospital emergence ward where the operator just needed a dial of phone keypad to control all the equipment in the room in case of emergence.

Below block diagram of DTMF circuit

DTMF circuit

Tx

This is the transmitter, in this circuit make use of phone that has airtime in it so that you can dial the receiver (rx)

Rx

This is the receiver, in this circuit make use of phone that will be connected to the dtmf decoder through handsfree or audio device. Rx can be used to control the dtmf circuit directly.

Input

The input here is the handfree or headset plug. With the configuration below. short aux-left & aux-right and connect to ground.

DTMF audio connector

DTMF circuit decoder

This unit comprises of MT8870 dtmf audio tone ic. It accepts the input from audio tone, interprets and output it by different keypads audio tone. You notice that when you dial a phone the numbers being dialed sounds different. For example 1 sound different from 2 and 3 and so on. 

Output (LED or Relay)

This unit is where you connect LED as indicator or relay as switch. In this particular dtmf circuit I used LED as indicator.This section can further be converted to switch by use of relay switch or any ic switch included.

Gadgets

This unit is the appliances you want to control.

How to configure a phone before is used for dtmf circuit.

After designing the circuit, it may not work if the phone is not properly configured. The first day I designed it a faced this challenge.

1. Go to settings

2. Go to  Enhancement

3. On the headset

4. Select auto answer

5. Finally remember to increase the keypad tone volume

If all is well connected and you construct your dtmf according to dtmf circuit diagram then everything will work. 

DTMF circuit diagram

Watch video of dtmf circuit detail here

https://www.youtube.com/watch?v=1_QuXn-9zEs&t=48s

DTMF Circuit components list

5V Power supplyRelay (optional)
Capacitors 2(22pf), 1(10uf)  1(0.1uf)
Resistors  2(100k)  1(330K)
Crystal Oscillator 1
Connecting wires
DTMF tone ic MT8870