RoboScan

This is the source code for a Lego+Raspberry Pi-powered analog film roll scanner. Watch it in action:

Parts

You'll need these items to build RoboScan:

• A digital camera with a macro lens: must be compatible with libgphoto2 with image capture and preview support.
• A Raspberry Pi: you may choose a Pi 4 if your camera supports USB 3, otherwise a Pi 2 or 3 is fine.
• A 28BYJ-48 Stepper Motor with ULN2003A driver: easy to find and cheap (about $6)
• 3D-print an adapter to integrate the stepper motor in the legos: use the stepper mount and axis adapter provided by this project (you'll need some bolts to attach the motor to the adapter): https://create.arduino.cc/projecthub/fredrikstridsman/lego-stepperbot-df26b9.
• Adafruit White LED Backlight Module.
• A LED driver such as Recom Power RCD-24-0.70/PL/B or Sparkfun FemtoBuck LED Driver.
• A 50V, 47 μF capacitor
• A high-power LED, such as New Energy LST1-01G03-4095-01: a 4000K white LED, with a CRI (Color Rendering Index) of 95.
• Build the lego part: https://www.mecabricks.com/en/models/r121kn4gvlB.

Part 1: Wiring

Diagram

(made using Fritzing with the help of parts from e-radionica.com and Blomquist)

ULN2003A wiring

Put a 50V, 47 μF capacitor between the LED+ and LED - pins of the driver.

Recom Power RCD-24-0.70/PL/B Backlight LED driver wiring

Alternative: Sparkfun FemtoBuck Backlight LED driver wiring

Untested - make sure to solder the jumper that can be closed with a glob of solder to double the output current from 330mA to 660mA.

Part 2: Software installation

Prepare the Raspberry Pi

Follow Raspberry foundation documentation, such as: https://projects.raspberrypi.org/en/projects/raspberry-pi-setting-up. Tip: you can set the hostname of your Raspberry Pi to "piscanner" as it's what's used in this tutorial. You can use raspi-config for this.

Install Docker

The easiest is to use the "convenience script" as described here: https://docs.docker.com/engine/install/debian/#install-using-the-convenience-script.

In a nutshell:

curl -fsSL https://get.docker.com -o get-docker.sh
sudo sh get-docker.sh
# Add your user to the docker group
sudo groupadd docker
sudo usermod -aG docker $USER

Install Python & PIP

On Raspbian, the easiest is to install it through Python's pip:

# Install Python3 and pip
sudo apt install python3 python3-pip

Clone this repository on your Raspberry Pi

git clone https://github.com/bezineb5/RoboScan.git
cd RoboScan

Start the application

Now, you will ask docker to build and start the application. This might take a while (30-120 minutes).

cd docker
docker compose up -d --build

It will start all components and restart them at reboot.

Part 3: Using RoboScan

The camera must be connected to the Raspberry Pi via USB. It must be compatible with libgphoto2.

Connect to the web interface

Simply navigate to http://piscanner/ (adjust the hostname to your Raspberry Pi)

Optional: Google Coral TPU

You can improve the machine learning inference performance by using a Google Coral Edge TPU USB Accelerator plugged on a USB port of the Raspberry Pi. To do so, you have to change the file src/Dockerfile. Replace:

CMD ["python", "webapp.py", "--destination", "/storage/share", "--archive", "/storage/archive", "--temp", "/storage/tmp"]

by:

CMD ["python", "webapp.py", "-tpu", "--destination", "/storage/share", "--archive", "/storage/archive", "--temp", "/storage/tmp"]

Optional: for developers

The easiest is to code on you PC and deploy docker containers remotely. To do so, enable remote access to the docker daemon.

# Set the DOCKERHOST variable (only once)
# Adjust the hostname to your Raspberry Pi
export DOCKER_HOST=tcp://piscanner.local:2376 DOCKER_TLS_VERIFY=

# Then deploy as usual
cd docker
docker compose up -d
cd ..