Talking Darkroom Timer

I got tired of having to mess with darkroom timers in the dark while processing colour prints in trays, so designed and built a timer that understands entire processes and walks you through them step-by-step with speech. The timer reads process information from paper instruction sheets using Aztec 2D barcodes and then times each required step.

Components

• Timer itself, located above the left side of the sink near the ceiling
  • Raspberry Pi 2
  • Adafruit LCD Plate
  • Proto Plate with RS232 level shifter for barcode reader
• Speaker above the timer
• 2D barcode reader mounted on the shelf aimed at the wall
• Control panel below the sink with the following controls:
  • Large green SELECT button
  • Navigation left/right control
  • Active/Standby toggle switch
• Aztec Code barcodes on each process sheet, which contain all timing information

Usage Procedure

• Set the Active/Standby switch on the timer control panel to Active
• Scan the barcode for the process you want under the crosshairs that appear on the wall
  • Barcodes can be found on instruction sheets for each process that are hung up behind the door.
• Double check that the timer is displaying the process you want to run, and press the big green SELECT button
• The timer may ask if you want to adjust the time for specific steps.
  • If you don't, just press SELECT.
  • If you do, use the navigation buttons to change to Yes and press SELECT.
• The timer will show and read out each step as it's ready.
• Press SELECT to start each step.
  • If you want to run a different step instead, use the navigation buttons to scroll through.
• To abort a step in progress, hold the SELECT button until you hear a buzzer.

Other Information

• To generate new barcodes, you can use the Darkroom Timer Barcode Generator
• There's a writeup of this project at the HackLab.TO blog