Darkroom Timer
simple… with a PIC!
Materials
Gerber file
CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.
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Component list
R1 =4 x 10kOhm SIL array
R2 =10kOhm
R3 =1kOhm 5
R4 =330Ohm
Capacitors:
C1-C4 =47nF
C5 =470µ F 16V radial
C6 =220µ F 16V radial
C7 =100nF
Semiconductors:
D1-D4 =1N4001
D5-D16 =1N4148
D17 =LED, red, high efficiency
IC1 =7805
IC2 =PIC16F84-04/P (order code 000182-41)
IC3 =S201S01 (Sharp) (Conrad # 16 81 65)
Miscellaneous:
K1,K2 =2-way PCB terminal block, 7.5 mm lead pitch
F1 = fuse, 0.5 AT (time lag), with PCB-mount holder
TR1 =Mains transformer 6 V, 1.5 VA (Conrad Electronics # 50 60 44)
S1,S2,S3 =BCD-encoded thumbwheel switch type PICO (Conrad 70 10 84)
2 spacers (Conrad Electronics # 70 11 06)
1 pair end cheeks (Conrad Electronics #70 11 33)
X1 =4 MHz resonator (Conrad Electronics # 50 31 69-55)
S4 = pushbutton, 1 make contact
S5 =SPDT changeover switch
Case: Teko 362 (Conrad Electronics # 52 39 68)
PCB, order code 000182-1
Disk, source and object code, order code 000182-11
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