HOW TO WORK DTMF CM8870 IC

you can operate Electric appliance by a bluetooth or wifi rf module etc.

but  all those  wireless methods work in a limited distance.

DTMF wireless application that can be controlled from any where on earth.

this process handle DTMF decoder 8870 IC.

DTMS means

 (dual tone multi frequency)

which is one of the techniques for converting the analogue signal to digital signal.

DTMF keypad is placed out on like a 4 *4 matrices, 

in which each row represents low frequency, 

each column represents high frequency, 

When a button is pressed from mobile it generates 2 tone which is of the specific frequencies 

one tone is generated from a high frequency tones and low frequency tone. 

These tones are converted into digital form using DTMF decoder circuit. 

 The DTMF decoder circuit used in many electronically  projects for better connectivity to control the applications.

The main objective of this project is to control the home applications like light, electric fan or something else by using DTMF techniques.

 The mobile is connected at one end of the circuit .with the help of this mobile phone jack. 

The mobile jack is consisting of two wires. 

this pin is connected to the decoder IC and other one is ground.

i set 5 volt in my power supply .

and power up this circuit.

and i call to the phone which is connected to the circuit from my cell phone

remember one think  you have to mute the call from your phone

because the DTMF IC generate noise beep kHz.

This ic will work according to this data shit.

when i pressed any key of phone ,those led  glow one by one, 

now the question is how to operated ac 220 volt .

thats why you obviously  need rely.

i used hear 12 volt 4 relay.

8870 IC could not handle 12 volt IC so i use hear  2003 IC.

other wise you can use here 4 transistor for drive those really.

this IC has 7 input and 7 out put.

and operate volt is 7 to 38 volt.

other hand this 8870 ic need 5 volt , thats why i use here 7805 regulator ic.

#2# um 2003 ic

#3# led green red and yellow

#4#  screw terminal 

#5#  7805 regulator ic

#6#  2.2k resistor

#7#  300k resistor

#8#  27 pf

#9#  104 pf

#10#  100k resistor

#11#   4007 diode

#12#   3.58 Mhz crystal oscillator

 #13#   220 mfd capacitor

diagram

Pcb Layout

https://drive.google.com/open?id=1yu0_f5KbrUpLBzQ3nRp3PDqC23e4qsIN


Gerber format
https://drive.google.com/open?id=1GYbMT-Gouw1eEuySAVy0vi5IqIAs3yRs