Darkroom Timer v2.0A for PCB Exposure Box

Post oleh : Unknown | Rilis : 06:32 | Series : Darkroom Timer v2.0A for PCB Exposure Box

This is an improved version of the Darkroom Timer originally created by Stan Ockers (1999). Some extra features were added and the PIC code was modified accordingly

 Lamp(s) light at start of timing and turn off when timer reaches zero. A set of leds were added between the minute and second leds which blink during timer operation. 7 segment displays include tails for digits 6 and 9. A bicolor led (common cathode) indicates standby (green) and timer operation (red). Separate PCBs were designed for the led display and the timing system. The power supply is also integrated in the PCB.

The complete schematic, PCB and silkscreen are available in high resolution pdf format. The component values are clearly indicated on the silkscreen. The modified source code is available in asm and hex format (compiled in MPLAB).

Darkroom Timer Schematic

Darkroom Timer PCB

Darkroom Timer Silkscreen

Parts list

 
System board

R1 - R7              150 Ω  1/4W 5%
R8 - R11             4.7 KΩ  1/4W 5%
R12 - R13           1 KΩ  1/4W 5%
R14                   100 Ω  1/4W 5%
R15                   75  Ω  1/4W 5%
R16                   10 KΩ  1/4W 5%
C1 - C2              22 pF
C3                     2200 μF/25V electrolytic
C4 - C6              100 nF  

D5                     1N4001/4004/4007
F1                     1A  Fuse (with socket and cap)
B1                     1A  Bridge rectifier
IC1                    PIC16F84AP Microcontroller (4MHz clock) (with IC socket)
IC2                    74HC4543 BCD to 7-segment decoder (with IC socket)
IC3                    7812 voltage regulator
IC4                    7805 voltage regulator
PL1                   14 pin connector
JP2                    6 pin header
K1                     12V DC / 220V AC Relay
OK1                   CNY17-1 Optocoupler                                                   

OSC1                 4MHz Crystal
Q1 - Q4             BC557/558 PNP Transistror
Q5                    BC547/548 NPN Transistor
Q6                    BC557/558 PNP Transistror
Q7                    2N2222 NPN Transistor
TR1                   220VAC/15VAC 1VA PCB Transformer                                                           

X1 - X3             2 pin WAGO screw clamp 

Led board

D1 - D4              Common cathode 7-segment display
LED1 - LED2        Orange Led 3 mm
JP1                    Not a connector, cable is soldered directly on the back of the led PCB

Box front

Bicolor common cathode led (green-red)
3 push-button switches           

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