Oki, why should I use this Event Phone Dialer?
In combination with an alarm system without any dial apparatus it make sence to add such phone dialer to inform the housekeeper about events when he is absent. The event could be a decoupled high or low active electrical signal (level generally 0..12V) taken from an alarm system, a water detector, a gas (CO/smoke) detector or any other detector. The event phone dialer calls one or more stored phone numbers as reaction of those events. In that case the housekeeper – assuming he has a (mobil) phone nearby – has been informed concerning appeared events in the house.
The Eagle Lite schematic is shown as pdf or schematic!
The event input consists of PAD4 as pulse sensitive low active signal that activates in case of 0V an input pad from the pic16f628a (RA3) via the optocoupler CNY17. The firmware of the pic programs the MT8880 DTMF transceiver (RBx/D0..3,PHI2,RS0,RW) to call phone numbers stored in the EEPROM of the pic. The call progress monitored by the MT8880 taken from the IRQ/CP pad (440 Hz pulse burst) is transformed to one puls per burst by the 74LS123 (retriggerable monostable multivibrator). The firmware measures the occurrence of these pulses (RB6) inside a corresponding time to notice when the callee picks up the (mobile) phone receiver. Two LEDs are available for debugging purposes!
The PCB of Eagle Lite can be seen as pdf or pcb!
The PCB has been prepared getting Eagle Lite restricted to support only boards with a dimension of 100 x 80. It consists of a bottom layer with some connections on the top layer. The LEDs are positioned on the left side, the connections for power, event input and phone line are placed on the right side.
The open source software of the pic16f628a can be downloaded as zip file! I compiled and bind all files by SDCC and GPUtils. Simulation has been performed by GPSim. All detailed descriptions of the software can be found in the source files themself! Feel free to modify the software if more functionality is required!
In case of changing the schematic or the software to add more features please contact me. I am very interesting in those modifications. Thanks!
Outlook: You can see the jumper JP2 in the schematic called ,Prog‘! This jumper is not used at the moment but can be used to program the phone numbers into the EEPROM of the pic16f628a. How does it mean? I do not know! What about you? Contact me if you have some ideas!
Remark: This application – more precisely the schematic – is based on the work of Alan Parekh’s ,Alarm Phone Dialer‘. Thanks a lot , Alan!
In January, I desided to change the microcontroller from the old pic16f84a to the new fashioned pic16f628a. The schematic is the same but the software really improves the quality and adapt the code to the new micro.
You can download the zip file via link extraction