Telephone Operated Remote Control Using PIC16F84A

This design controls up to 8 devices using a PIC microcontroller (PIC16F84A) connected to the phone line. The unique feature here is that unlike other telephone line based remote control, this device does not need the call to be answered at the remote end so the call will not be charged. This device depends on number of rings given on the telephone line to activate/deactivate devices.

Set the DIP SWITCH as follows:

Switch RA4   Switch RA3      No. of initial rings to Switch ON(activate half of the board)

OFF        OFF             2

ON         OFF             4

OFF        ON              3

ON         ON              5

The number of initial rings to Switch OFF is one more than the number of rings to switch ON. For example, if you have set switch RA3 OFF & Switch RA4 ON then number of initial rings to activate half of the board to switch ON the relays is 3 and number of initial rings to activate half of the board to switch OFF the relays is 3+1 = 4

Switch RA1        Switch RA2        Delay before making the second set of rings

OFF                       OFF                   5 sec

ON                        OFF                   10 sec

OFF                      ON                     15 sec

ON                        ON                     20 sec

This is the maximum delay the board can take after it is half activated. It will reset after this delay.

 Now connect the circuit to the phone line and switch on its power supply.

You can test the board now. For example set the DIP switch to Switch RA1 OFF, Switch RA2 ON (15 sec delay) & switch RA3 OFF, switch RA4 ON (4 rings to activate half for switching ON). If you want to switch ON relay 1 (connected to RB0 of main circuit) then you have to do the following:

1. Give 4 rings and put down the receiver
2. Wait 5 seconds (this 5 seconds wait is required to prevent the board from detecting continous rings)
3. then within 15 seconds give 1 ring (1 ring for relay1, 2 rings for relay2 and so on) and put down the receiver
4. then within 5 sec the relay1 will switch ON

To switch off relay1:

1. Give 5 rings and put down the receiver
2. Wait 5 seconds (this 5 seconds wait is required to prevent the board from detecting continous rings)
3. then within 15 seconds give 1 ring (1 ring for relay1, 2 rings for relay2 and so on) and put down the receiver
4. then within 5 sec the relay1 will switch OFF

Download: Schematic and Program files

Schematic:

Components Required:

U1,                                   PIC16f84A

U2,                                  7805

U3,                                  MCT2E (mistake in sch)

U4,                                  555 Timer

D1,                                  1N4007

D2-D3,                           10v Zener Diode

D4,                                  1N4007 (plus seven more)

R1-R4,                            2.2K ohm

R5,                                  2.2K ohm (plus seven more for relays)

R6,                                  10K ohm, 1 watt

R7,                                  15K ohm

C1-C2,                             22pF Ceramic cap

C3-C4,                            100nF Ceramic cap

C5-C6,                            100uF / 25v Electrolyte cap

C7,                                  470nF/200v

C8,                                  47uF / 25v Electrolyte cap

Q1-Q8,                           BC547

RL1-RL8,                       12v Relay 

DSW1,                            4-way dip switch