Welcome to this simple DTMF notification by Cell phone Schematic.
1). In the schematic below I have designed a simple notification Devise for any DTMF Decoders that use the MT8870,CM8870 or HT8170 Chips in there design.
2). How the circuit works is simple when you send a DTMF tone to the decoder the value of pin 15 goes high for a short time this makes an excellent trigger as it supplies a few volts to pin 2 of the 555 Timer this triggers the circuit and turned the relay on for a short time. If you want different times you can experiment with R1 use a Potentiometer or a preset one.
3). Now as soon as Pin 2 on the 555 Timer has a few volts at the Trigger input of pin 2 this will switch the relay over for about 5 seconds if you have set one touch dial or speed dial on your Modified Cell phone then this will call you letting you know it has received valid DTMF tones.
4). It would be best to have this go to a mobile phone if you are still connected to the DTMF Decoder then it would be best to turn your Answer phone off before you make the call to the DTMF Decoder as the sending back phone will call what number is locked in it's memory.
5). Now most Cell phones have a time delay of 2 or 3 seconds when touch or speed dial is activated this simple design gives you 5 seconds then it switches back waiting for the next time you connect to the DTMF Devise to activate it again.
6). The design is simple to follow it would be a good idea if you set on the transmitting phone the Auto Re-dial you have to turn your answer phone off on your receiving phone just in case it went to answer phone.
7). Now setting the Auto Redial on the sending back mobile phone is good as if you did not disconnect in time it will just phone your again then you just disconnect the incoming call as it has showed on your Screen what call is coming in.
8). In this design I have used a back up Modified cell phone for the Re-sending of the notification signal to me the incoming call does not need to be answered just disconnect the incoming call and you will not be charged for the call.
9). On your receiving Mobile phone put the name in like DTMF Call and it's number this is letting you know the DTMF Decoder received your command and has sent you a notification signal.
10). This simple design can work with any type of IC that goes high and you need a notification the uses are endless.
In the Schematic below I have designed a simple timer for the following IC's this will allow a load to be connected till switched off or on the second relay is a Timer for 5 seconds, I designed this to send a notification signal to let me know my DTMF signal was received ok.
In the Schematic below I have connected my two Schematics together to show how they can be connected up.
Here is the Schematic on how to connect your circuit to the Cell phone below.
Please note if you have any problems and need help then please do e-mail me here: Anthony@anthony-dacko.net
My Electronics page.