Darkroom Timer – Full Details

Darkroom Timer Schematics JPGHere is a list of everything you need to build the Timer:

Parts you will need:

1 x Arduino Uno or compatible Board
1 x 5V Power supply
1 x 12V Power supply
1 x Breadboard or compatible routing board
6 x 40-50k Resistors
6 x Generic Diodes
2 x Dual input OR 3 x single input Relays(12v trigger, 240v current or 120v or whatever your country has)
3 x 7 Segment Common Cathode RED LED Display Modules
3 x 4511 7 Segment Latch Enabled Drivers
3 x Generic NPN Transistors
1 x Manual Flick Switch
5 x Push-button Switches
1 x Enclosure, I used a plastic box used in outdoor alarm boxes(you can get these at any electronics/hardware store)
1 x Female Jug Plug
1 x 240v/120v Female Socket

Here is a bit of a layout guide:


2 thoughts on “Darkroom Timer – Full Details

  1. Florin


    I have done my own solution using a small FPGA developing board and solid state relay. I haven’t use it in the darkroom yet…maybe next week. I was wondering how safe is the light radiating from the red LED 7 segment display? It will interfere with the printing process? For me looks quite bright.

  2. Leon

    The red light from the display does not dog paper at all. I tested it out before putting it all together.

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