Digital Timer-Clock With Relay
9v 300 mA Wall wart (AC -> DC adaptor)
PIC16F628a (You will need a programmer as well, REMEMBER TO PROGRAM THE CHIP BEFORE YOU SOLDER IT TO THE BOARD !!)
CD4511 BCD to 7-seg driver chip
LM7805 - 5V regulator
Relay - with 5v coil
4 x Common cathode 7-seg displays
5 x 2N3904 NPN transistor (or similar)
4 Mhz crystal
4 x 22 K resistors (R1,R2,R3,R4) (any value between 15 K and 33 K should do though)
5 x 1 K resistors (R5,R13,R14,R15,R16)
2 x 470 Ohm resistors (R17, R18*)
7 x 180 Ohm resistors (R6,R7,R8,R9,R10,R11,R12)
C3 - 1000 uF electrolytic cap,16V or better
C4,C5,C6 - 10 uF to 100 uF electrolytic capacitors, 16V or better
C1 and C2 - 10pF ceramic cap
4 x 2pin tactile push buttons.
2 x 2-position terminal blocks
*R18 is optional, it will make the right most dot point light up when the relay is on.
Holes joined with a line on the silk screen should be connected with a jumper link or wire.
Note that the schematic does not fully match with PCB layout, some changes has been made.
NOTE: The Displays must be placed on the back side, in this version ! (Trace-layer).
The Displays are the common cathode type.
PCB Layout (DipTrace) - Relay-Timer-7seg.dip
Schematic (First version, some changes have been made in the layout file) - Timer_sch.jpg