Polargraph

Have a hard time deciding what to hang on your walls? Boy, do I have the solution for you.

Wall mounted, web accessible polargraph pen plotter. Full project writeup at teddywarner.org/Projects/Polargraph.

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All project CAD may be found in the hardware directory in this repo. Full assembly instructions may be found in the full project writeup.

BOM

Qty	Description	Price	Link	Notes
1	Raspberry Pi 5	$89.94	Link	8GB
1	Raspberry Pi 5 Active Cooler	$9.90	Link
1	Micro SD Card	$16.68	Link	≥32GB
1	RAMPS 1.4 Shield	$9.39	Link
2	A4988 Stepper Drivers	$9.98	Link
2	Nema 17 Pancake Stepper	$21.00	Link	42mm x 23mm
1	MG90S Micro Servo	$9.99	Link	9G
2	Stepper Motor Cables	$10.99	Link	2M length
2	GT2 Timing Belt	$19.98	Link	6mm width, 5M length
2	GT2 Timing Belt Pulley	$6.99	Link	16 Teeth, 5mm bore
2	6806-2RS Ball Bearings	$30.00	Link	30mm x 42mm x 7mm
1	12V Power Supply	$35.00	Link
1	DC/DC Buck Boost	$9.99	Link
1	C14 AC Inlet	$9.04	Link
1	AC Power Cord	$9.39	Link	Down angle
-	14 Gauge Wire	$13.99	Link	A couple feet
2	Limit Switch	$5.99	Link
3	Tungsten Weights	$89.97	Link
1	1/4" Maple Plywood	$37.71	Link	4'x8' sheet
4	1"x3" Spruce Pine Boards	$27.92	Link	8' length
1	Wood PLA	$25.99	Link	1.75mm, 1 spool
1	A0 Paper Roll	$29.86	Link	36" x 1200"
1	SAKURA Pigma Micron 05 Pens	$20.97	Link	Multicolor pack
1	French Cleat	$31.00	Link	30 in. 300 lbs.
1	Felt Pads	$9.97	Link	Assorted Pack
-	M2 and M3 Hardware	-	-	Misc nuts and bolts
-	Jumper Wires	-	-	Misc

Total: ~$595.82

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Raspberry Pi Setup

Flash Raspberry Pi OS Lite (64-bit) and configure WiFi. SSH in:

ssh pi@raspberrypi.local
sudo apt update && sudo apt upgrade -y

Set hostname to plotter:

sudo hostnamectl set-hostname plotter
sudo nano /etc/hosts  # Change 127.0.1.1 to plotter
sudo reboot

Install dependencies:

sudo apt install -y python3-pip python3-venv avahi-daemon git
sudo systemctl enable avahi-daemon

Clone Repository

git clone https://github.com/Twarner491/polargraph.git ~/polargraph
cd ~/polargraph
python3 -m venv venv
source venv/bin/activate
pip install -r requirements.txt

USB Permissions

Set permissions for the plotter's USB serial connection:

sudo cp system-config/99-polargraph.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules && sudo udevadm trigger
sudo usermod -a -G dialout pi

Start Flask Server

Enable the service to auto-start on boot. If your username is not pi, edit the service files first to replace /home/pi/ with your home directory:

# Edit if needed: nano system-config/polargraph.service
sudo cp system-config/polargraph.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now polargraph.service

Access at http://plotter.local

Home Assistant Integration (Optional)

For remote access via plotter.onethreenine.net → Home Assistant → MQTT → Pi.

Home Assistant Automation

Add to automations.yaml:

alias: "Polargraph Command"
trigger:
  - platform: webhook
    webhook_id: polargraph_command
    allowed_methods: [POST]
    local_only: false
action:
  - service: mqtt.publish
    data:
      topic: "home/polargraph/command"
      payload_template: "{{ trigger.json | tojson }}"

Enable CORS

Add to configuration.yaml:

http:
  cors_allowed_origins:
    - https://your-domain.com

Pi MQTT Setup

Create a .env file in the polargraph directory with your MQTT broker settings:

MQTT_BROKER=192.168.1.XXX
MQTT_PORT=1883
MQTT_USER=
MQTT_PASS=

Then enable the MQTT service:

pip install paho-mqtt
sudo cp system-config/polargraph-mqtt.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now polargraph-mqtt.service

Frontend Configuration (GitHub Secrets)

To enable remote access on your fork, add these GitHub Secrets to your repository:

1. Go to your fork's Settings → Secrets and variables → Actions
2. Add the following secrets:

Secret Name	Value
REMOTE_WEBHOOK_URL	Your Home Assistant webhook URL (e.g., https://your-ha.duckdns.org/api/webhook/polargraph_command)
REMOTE_ACCESS_KEY	A password of your choosing for activating remote mode

3. Push any change or manually trigger the Deploy to GitHub Pages workflow

Once deployed, enter your access key in the Console tab to activate remote mode.

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