OwnTracks Server

You'll need to set GOOGLE_API_KEY (could put it in env.sh)

Local test

npm install
PORT=8888 npm start

Using curl with basic auth

curl -v -u testuser:hello \
  -H "Content-Type: application/json" \
  -d '{"_type":"location","lat":40.7128,"lon":-74.0060}' \
  http://localhost:8888/pub

Interacting with Dynamo

Freshen up the local temp credentials:

aws sts get-session-token --duration-seconds 3600 | jq -r '.Credentials | "[default]\naws_access_key_id=\(.AccessKeyId)\naws_secret_access_key=\(.SecretAccessKey)\naws_session_token=\(.SessionToken)"' > ~/.aws/credentials

Create a new user

This will create a new user named ch in friend-group friends:

AWS_REGION=us-east-2 AWS_PROFILE=default PORT=8888 npm run dynamo-ops create-user ch friends

Whatever password is used in the next location update will be accepted and stored.

Local test with DynamoDB

AWS_REGION=us-east-2 AWS_PROFILE=default DYNAMO_MODE=true PORT=8888 npm start

AWS Lambda Deployment

Prerequisites

• AWS CLI configured
• AWS S3 bucket for Lambda deployment

Deployment Steps

S3BUCKET=your-bucket-name ./deploy.sh

Physical locograph

Parts list

Most of these parts can be substituded with a similar alternative. Amazon links are only provided for convenience, not as strong recommendations.

1. one raspberry pi pico 2 w -- with headers ($8)
2. one usb port for power ($6)
3. one button for calibrating the hands ($6)
4. for each clock hand a stepper motor with driver board ($15)
5. lots of female-to-female breadboard jumper wires, roughly 6 per hand plus 4, so 35 should be enough ($5)
6. to mount the motors to the hub, "6-32 x 1/2inch" machine screw and matching nut times 2 for each hand (for five hands, 10 screws and 10 nuts) ($2 at local hardware store)
7. to mount the driver boards to the box, "#6 x 1/2inch" flat head wood screws times 4 ($1 at local hardware store)

Also requires a bit of soldering, 3d printed parts (I used PETG), and laser-cut parts (5mm plywood for the box, 1.5mm basswood for the hands).

That comes to about $40 assuming you already have the wood, plastic, tools, solder, etc.

Hosting the server on AWS looks like it's costing about $0.05/month.

Step 1: Software Setup and Initial Wi-Fi Test

Install Thonny IDE:

• Download and install Thonny from https://thonny.org/
• Connect your Raspberry Pi Pico to your computer via USB
• Open Thonny and go to Tools → Options → Interpreter
• Select "MicroPython (Raspberry Pi Pico)" as the interpreter
• Ensure the correct port is selected

Upload files to the Pico:

• In your local GitHub working copy, locate in the pico-code directory the files:
  • main.py
  • secrets.py (customize this based on the example provided)
• In Thonny, open each file from your local directory (File → Open)
• To upload to the Pico: File → Save As → select "Raspberry Pi Pico" as the destination
• Save both files to the root directory of the Pico
• The files should now appear in Thonny's file panel under the Pico device

Test Wi-Fi connection:

• In Thonny, click the "Run" button or press F5 to execute main.py
• Check the console output for Wi-Fi connection confirmation messages
• Verify successful startup indicators

Step 2: Pico Wiring - Connect All Electrical Components

General approach: The Pico has plenty of ground pins, so use one for each stepper motor driver board. But for VCC you'll have power coming only from the separate micro-USB port, so you'll need to solder several wires together to supply the Pico, and all the drivers.

Power connections:

• Connect USB power ground to Pico ground
• Solder together several jumper wires to create a VCC power bus
• Connect USB power pin to:
  • Raspberry Pi Pico VCC
  • Each driver board VCC (up to 5 boards)

Up to 5 stepper motor driver boards:

• Use ribbon cables of 5 breadboard jumper wires for each driver board (4 GPIO + 1 ground)
• Note the GPIO pin numbers and update steppers in secrets.py. The numbers used in the py files are the GP pin numbers.

Calibration button:

• Connect one side to a GPIO pin on the Pico
• Connect other side to ground
• Note the GPIO pin number and update button_pin in secrets.py.

Step 3: Stepper Motor Movement Testing

• Connect stepper motors to driver boards using their built-in connectors
• Run main.py again in Thonny
• Verify the system enters calibration mode
• Use the calibration button to step through each stepper motor calibration
• Important: Ensure all motors are turning clockwise
  • If any motor turns the wrong way, reverse the order of the GPIO pin numbers in secrets.py for that stepper
• Once all motors are calibrated and turning correctly, you may want to unplug the steppers from their driver boards to make the next assembly steps easier

Step 4: Driver Board Mounting

• Fit driver boards over the pegs on the rails
• Sandwich the other half of the rails on top
• Use wood screws to mount the assembled rails to a side wall of the box

Step 5: Stepper Motor Mounting - Attaching Motors to the Hub

• Mount the small driver gears onto the stepper motors
• Fit hex nuts into the retaining slots on the hub posts
• Fit the five-armed brace over the screw holes
• Add the stepper motors (positioned so gears will mesh properly)
• Thread machine screws through the stepper motor holes, through the brace holes, through the hub post holes and into the hex nuts, and tighten them down

Step 6: Hub Movement Testing

• Reconnect the stepper motors to their driver boards
• Run the calibration sequence to test basic movement
• Optional: Enable "Demo Mode" in main.py, which moves the hands to random positions a couple times per minute allowing you to observe the mechanics.
  • Look for gears binding or catching, and reposition driver gears if needed
  • Add silicone lubricant between gear layers or anywhere else that's rubbing or squeaking

Step 7: Final Assembly

• Fit the sides, back, and hub support panels together
• Set the hub into the support panel
• Fit the front panel over the hub
• Place this whole assembly into the floor panel
• Add the roof on top
• Mount the clock hands onto the hub
• Admire your handiwork.

Copyright 2024 Chris Houser