FPP-3 Film/Paper Processor - Arduino Controller (v5.1.2)

Author: Luis Samaniego

FPP-3 is an Arduino UNO based controller for a home-built rotary film/paper processor (JOBO tanks). It drives a DC motor through an H-bridge, shows DEV/TEMP information on a 20x4 I2C LCD, and is operated via a 4x4 keypad.

This repository contains:

• rotary_processor.ino : current firmware (v5.1.2 tag)
• src_old/ : archived older firmware versions (v3, v4, etc.)

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Features (v5.1.2)

• Two user pages:
  • DEV page: timing + motor run/stop + step recall/store
  • TEMP page: temperature monitoring + profile selection + PREHEAT start/stop
• Rotary motor control:
  • Smooth acceleration/braking
  • Periodic direction reversal
• EEPROM persistence:
  • Last used timing (min/sec)
  • Last selected profile
  • Calibration offsets (0.1 C) for Bath/Tank/Bottle and Heater (HTR)
  • 9 development step presets (1..9)
• DS18B20 temperature sensors (1-wire) via OneWire + DallasTemperature
  • ROM-based assignment (addresses stored in code)
  • Kodak thermometer reference offsets stored in EEPROM (0.1 C)
• Darkroom mode:
  • LCD backlight toggle via keypad combo

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Hardware overview

Typical build:

• Arduino UNO (or compatible)
• IBT-2 / BTS7960 H-bridge motor driver
• DC motor driving JOBO roller base
• 20x4 I2C LCD (LiquidCrystal_I2C)
• 4x4 matrix keypad
• Buzzer
• DS18B20 sensors (Bath, Tank, Bottle) on one 1-wire bus

Power:

• 12 V for motor (via external supply)
• 5 V for UNO + sensors (via DC-DC converter)

IMPORTANT:

• Keep motor power and logic power grounds common (single reference).
• Keep sensor wiring neat; use proper pull-up on the 1-wire data line.

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Arduino libraries

Required includes (as used in v5.1.2):

• <Wire.h>
• <LiquidCrystal_I2C.h>
• <Keypad.h>
• <EEPROM.h>
• <OneWire.h>
• <DallasTemperature.h>

Install missing libs in Arduino IDE: Tools -> Manage Libraries... Search and install:

• "OneWire" (Paul Stoffregen)
• "DallasTemperature" (Miles Burton)

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DS18B20 wiring (1-wire)

• DS18B20 VDD -> +5V
• DS18B20 GND -> GND
• DS18B20 DQ -> chosen Arduino pin (your "DG" / data pin)
• Pull-up resistor between DQ and +5V:
  • Typical: 4.7 kOhm (5% OK)
  • 100 nF ceramic capacitor between +5V and GND near the sensor side.

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User interface

Pages and modes

• Pages:
  • PAGE_DEV : development timing + motor control
  • PAGE_TEMP : temperature monitoring + PREHEAT + profile selection
• Run modes:
  • MODE_IDLE : not running
  • MODE_DEV : motor running with countdown
  • MODE_PREHEAT : temperature preheat control active
• Calibration:
  • CAL mode entered from TEMP page when IDLE (see below)

LCD menu row (20 chars) follows the v5.1 patched UX:

• DEV page: shows A/B timing, C Go/Stop, D Pg
• TEMP page: shows A/B profile, C Go/Stop (PREHEAT), D Pg

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Keypad commands

Keypad has: digits 0..9, A/B/C/D, * and #.

Global (works from ST_WAIT)

Keys	Action
*	If backlight OFF: turn ON. If ON: arm "OFF combo".
* then #	Turn LCD backlight OFF (darkroom). Must be within ~1 s.

DEV page (PAGE_DEV)

Keys	Action
A	Edit minutes (enter minute edit state)
B	Edit seconds (enter second edit state)
C	Go/Stop DEV run (toggle)
D	Switch page DEV <-> TEMP
1..9	Recall stored step (if defined)
# then 1..9	Store current time into step slot 1..9

Notes:

• "Store step" is a short sub-mode: press #, then one digit 1..9.

TEMP page (PAGE_TEMP), MODE_IDLE

Keys	Action
A	Profile forward (cycle)
B	Profile backward (cycle)
C	Start/Stop PREHEAT (toggle)
D	Switch page TEMP <-> DEV
0	Toggle TEMP diagnostics display (if enabled in firmware)
# ... #	Jump to profile by ID (1-2 digits) e.g. #15#

Profile jump notes:

• Start: press #
• Enter 1 or 2 digits (profile ID)
• Confirm: press # again
• Example: #1#, #9#, #15#

Enter CAL mode (TEMP page, IDLE only)

CAL entry combo (kept as in v5.1 patched UX):

• Press A then B within ~800 ms -> enter CAL.

CAL mode keys (all CAL pages)

Keys	Action
A	+0.1 C
B	-0.1 C
C	Save (write to EEPROM)
D	Exit (discard)
#	Next CAL page
*	Previous CAL page

CAL pages include:

• HTR (heater suggested setting)
• Bath/Tank/Bottle offsets (Kodak thermometer reference)

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Profiles

profiles[] defines the working presets (film and paper).

In v5.1.2 you use (example):

• Film:
  • BW 25.0 C (typical)
  • C41 38.0 C
  • E6 38.0 C
• Paper:
  • BW 20.0 C
  • RA4 35.0 C with small volumes and different mixing dynamics.

Each profile includes:

• id (shown/used for jump selection)
• chemistry label ("BW ", "C41", "E6 ", "RA4")
• setpoint (0.1 C)
• tank code (e.g., 2521, 2551, 2561, 2821, ...)
• chemistry volume (mL)
• dT_pour_10 initial pour cooling in 0.1 C (developer enters cooler)
• boost time (s) optional pre-boost window
• dT_boost_10 optional boost magnitude in 0.1 C

Operational meaning:

• dT_pour_10 is applied once at DEV start as the initial condition for Tdev*.
• The lag model (Tdev*) then relaxes toward the chosen driver temperature.

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State machine (high-level)

stateDiagram-v2
    direction LR

    [*] --> ST_DISPLAY_MAINMENU
    ST_DISPLAY_MAINMENU --> ST_WAIT: draw current page<br/> (DEV or TEMP)

    %% -------------------------
    %% DEV PAGE (PAGE_DEV)
    %% -------------------------
    ST_WAIT --> ST_SETTIMING_M: (DEV) A minutes
    ST_WAIT --> ST_SETTIMING_S: (DEV) B seconds
    ST_WAIT --> ST_STARTMOTOR:  (DEV) C Go/Stop (DEV)
    ST_WAIT --> ST_DISPLAY_MAINMENU: (DEV) D page->TEMP

    ST_SETTIMING_M --> ST_DISPLAY_MAINMENU: # confirm / * cancel
    ST_SETTIMING_S --> ST_DISPLAY_MAINMENU: # confirm / * cancel

    ST_STARTMOTOR --> ST_DISPLAY_MAINMENU: runMotor(START) <br/> runMode=DEV
    ST_WAIT --> ST_IDLE: (DEV) C (while running) <br/> Stop
    ST_IDLE --> ST_DISPLAY_MAINMENU: runMotor(FORCESTOP) <br/> runMode=IDLE

    %% -------------------------
    %% TEMP PAGE (PAGE_TEMP)
    %% -------------------------
    ST_WAIT --> ST_PREHEAT: (TEMP) C Go/Stop (PREHEAT)
    ST_PREHEAT --> ST_WAIT: runMode=PREHEAT <br/> motor single dir
    ST_WAIT --> ST_IDLE: (TEMP) C (while preheating) <br/> Stop

    ST_WAIT --> ST_DISPLAY_MAINMENU: (TEMP) D page->DEV

    %% -------------------------
    %% CALIBRATION (TEMP only)
    %% -------------------------
    ST_WAIT --> ST_CAL: (TEMP+IDLE) A+B within 800 ms
    ST_CAL --> ST_DISPLAY_MAINMENU: C Save
    ST_CAL --> ST_DISPLAY_MAINMENU: D Exit (discard)
    ST_CAL --> ST_CAL: A +0.1 / B -0.1
    ST_CAL --> ST_CAL: # next / * prev

    %% keep the loop explicit (Mermaid likes it)
    ST_WAIT --> ST_WAIT

    note right of ST_WAIT
      DEV page:
        1..9      recall stored step
        # + 1..9  store current time in step
      TEMP page:
        A next profile (A-alone)
        B prev profile
        #..# jump to profile id (e.g. #15#)
        0 toggle diag
      Global:
        * backlight ON
        * + # backlight OFF
    end note

Loading

Changing Displays:

flowchart LR
  DEV[PAGE_DEV];
  TEMP[PAGE_TEMP];
  CAL[CAL];

  DEVK["A: minutes <br/> B: seconds <br/> C: Go/Stop <br/> 1..9: recall <br/> #: store"];
  TEMPK["A: next <br/> B: prev <br/> A+B: CAL (IDLE) <br/> C: preheat <br/> #..#: jump <br/> 0: diag"];
  CALK["A: +0.1 <br/> B: -0.1 <br/> C: Save <br/> D: Exit discard <br/> #: next item <br/> *: prev item"];

  DEV -->|D| TEMP;
  TEMP -->|D| DEV;

  DEV --> DEVK;
  TEMP --> TEMPK;

  TEMP -->|"A+B (IDLE)"| CAL;
  CAL --> CALK;
  CAL -->|D| TEMP;
  

Loading

---

How it operates (typical workflow)

A) Film development (DEV run)

1. Switch to DEV page (key D if needed).
2. Select a chemistry/tank profile (normally from TEMP page, then return to DEV).
3. Set development time:
   • A -> enter minutes, type digits, # to finish, * to cancel
   • B -> enter seconds, type digits, # to finish, * to cancel
4. Start development rotation:
   • Press C (Go). Motor starts, countdown begins.
5. Optional: store this time as a preset step:
   • Press # then 1..9
6. End:
   • Motor stops automatically at 00:00.
   • A short beep occurs ~5 s before end (one-shot).
   • Menu returns after a short delay.

B) Preheating (TEMP run)

1. Switch to TEMP page (D if needed).
2. Choose the profile (setpoint) that matches your process.
3. Press C to start PREHEAT rotation.
4. Wait until Bath temperature stabilizes in-band (READY latch).
5. Stop PREHEAT:
   • Press C again.

C) Calibration (match DS18B20 to Kodak thermometer reference)

1. TEMP page must be active and MODE_IDLE (not preheating, not developing).
2. Enter CAL:
   • Press A then B within ~800 ms.
3. Navigate CAL pages:
   • # next, * previous
4. Adjust offset:
   • A +0.1 C, B -0.1 C
5. Save:
   • C writes offsets to EEPROM
6. Exit without saving:
   • D discards and returns

Recommended practice:

• Calibrate Bath, Tank, Bottle at the temperatures you actually use (e.g. 20C and 38C), because small sensor non-linearities can exist.

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Installation

1) Software prerequisites

• Arduino IDE (2.x recommended)
• Board: Arduino UNO (or UNO-compatible)

Libraries used in v5.1.2:

• Wire
• LiquidCrystal_I2C
• Keypad
• EEPROM
• OneWire
• DallasTemperature

Install missing libraries: Arduino IDE -> Tools -> Manage Libraries... Search and install:

• "OneWire" (Paul Stoffregen)
• "DallasTemperature" (Miles Burton)

2) Build configuration (firmware switches)

In the sketch header:

• USE_DS18B20
  • 0: simulated/proxy temps
  • 1: real DS18B20 reads (DallasTemperature)
• DS18B20_SCAN
  • 1: prints ROM scan to Serial (for mapping sensors)

Serial:

• Baud: 57600

3) DS18B20 wiring (1-wire)

• DS18B20 VDD -> +5V
• DS18B20 GND -> GND
• DS18B20 DQ -> chosen Arduino pin (1-wire data)
• Pull-up resistor between DQ and +5V:
  • typical: 4.7 kOhm (recommended)
  • 5.1 kOhm often works for short cables but 4.7 k is the default

Optional (recommended with long cables / noise):

• 100 nF ceramic capacitor between +5V and GND near the sensor end.

4) First-time sensor mapping

1. Enable ROM scan (if not already):
   • USE_DS18B20 = 1
   • DS18B20_SCAN = 1
2. Upload firmware.
3. Open Serial Monitor (57600 baud).
4. Copy the ROM code printed for each sensor and paste into:
   • addrBath, addrTank, addrBottle
5. Label cables physically (recommended):
   • "Bh", "Tk", "Bo"

5) EEPROM reset (optional)

If you change EEPROM structure version, the firmware resets settings automatically when settings.version != SETTINGS_VERSION.

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Software overview

Main components:

• State machine with the following states (see figure):

  • ST_DISPLAY_MAINMENU
  • ST_WAIT
  • ST_SETTIMING_M (edit minutes)
  • ST_SETTIMING_S (edit seconds)
  • ST_STARTMOTOR
  • ST_IDLE

• Motor control:

  • Bidirectional rotation (CW / CCW)
  • Acceleration, constant speed, and braking phases
  • Direction reversal after nFullRev tank revolutions

• EEPROM persistence:

  • tMinutes, tSeconds (last-used timing)
  • 9 development steps (1..9) with minutes, seconds, and "defined" flag

The main loop performs:

1. Reads the potentiometer and updates tank RPM (with anti-jitter filter).
2. Calls runMotor(MOTOR_CONTINUE) to maintain motor state.
3. Updates the countdown display while the motor is running.
4. Handles keypad input depending on the current state.

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Licensing

• FPP-3 software is licensed under the GNU General Public License, version 3 or (at your option) any later version. See the file COPYING for the full license text.

• FPP-3 hardware design files (mechanical and electrical) are licensed under the license documented in LICENSE-HARDWARE.md.

• Additional details and third-party attributions are documented in LICENSE.md.