Laser projector

Raspberry Pi RGB laser projector

A vector laser projector with an easy to understand UI.
UI includes:

• integrated display control with a rotary encoder,
• web server on the local network
• discord bot accesible when the RPi is online

table of contents

• Raspberry Pi RGB laser projector
  • table of contents
  • thesis
  • how to install
  • supported projection file formats
  • hw
    • galvos
      • DAC - mcp4822
      • amps - TL082
    • laser
    • LCD + encoder
  • sw
    • communication
    • lasershow
    • UI
    • web_ui
    • discord_bot
    • wifi_manager
    • comms format
      • lasershow comms
        • basic commands:
        • responses:
      • wifi_manager comms

thesis

I wrote a whole thesis in czech language about this project. It is available in this repository (direct link to the pdf file).

how to install

git clone https://github.com/phuid/laser_projector.git
cd laser_projector
bash install.sh

this script installs all the dependencies of my programs and sets up the RaspberryPi to start all the programs on boot using pm2.

supported projection file formats

The projector can read and project .ild and (much more popular) .svg file formats. .ild files can be generated using specialised software like laserworld showeditor. .svg files from any editor are internally converted to .ild using this svg2ild.py script from gh/marcan/openlase

hw

My plans include battery power, usually galvos come with a power supply and powering the laser isn't that hard using a step-up. My module takes around 0.45A @ 9V. Make sure you dont brick your pi by taking its power. Raspberry Pis often don't take it well when an undervoltage occurs on their 5V line and they certainly aren't made to power anything more than an LED from their 3.3V PS.

galvos

take -10 to +10V differential signal between to lines (base and inverted), The DAC + opamps circuit which generates this signal is nicely described in this article. My implemetation of it in kicad files can be found in pcb/kicad.

DAC - mcp4822

DAC controlled by the RPi creates an analog signal between 0 and 5V.

amps - TL082

TL082 from texas instruments, each channel has one chip, each chip has two op amps. One opamp inverts and modifies the signal based on the potenciometers (getting the inverted ILDA signal), Second opamp inverts it again for the base ILDA signal

laser

rgb laser module from https://www.laserlands.net/diode-laser-module/rgb-combined-white-laser-module/11010003.html requires 8.5-12V power takes 35kHz TTL / PWM on 3 pins, these pins are connected directly to the raspberry pi

pin connections between the laser module and RPi

LCD + encoder

Any 20x4 LCD with an I2C backpack + any rotary encoder with a button LCD connections:

encoder connections:

sw

2 backend programs (lasershow (c++) + wifi_manager (node.js)) and 3 frontend programs (UI (c++) + web_ui (node.js) + discord_bot (node.js))

communication

each backend has its pub/sub sockets lasershow publishes to tcp://localhost:5556 and receives commands from tcp://localhost:5556 wifi_manager publishes to tcp://localhost:5558 and receives commands from tcp://localhost:5559

lasershow

• backend program that takes care of the actual projecting through controlling the galvos and the laser module

UI

• allows control of backend programs through the built-in LCD and encoder

web_ui

• allows control of backend programs through a web interface available on the local network

discord_bot

• allows control of backend programs through a discord bot

wifi_manager

• allows switching between three modes of wifi:
  • wifi off (stealth)
  • wifi on (wifi) -- RPi wifi on and trying to connect to known nearby networks
  • access point (hotspot) -- RPi wifi on transmitting its own wifi which other devices can connect to

comms format

lasershow comms

lasershow executable takes commands from all UI processes through a ZeroMQ TCP socket command format COMMAND + + ARG1 + + ARG2 + + + ARG4 -> parse with a simple while loop lol no need for fancy functions

basic commands:

any process can send a command into the socket and all processes will read responses from lasershow executable

• PROJECT args: <filename>
  • <filename> must have extension .ild otherwise error INVALID_ARG
• STOP (no args)
• PAUSE (no args)
• GAME args: <game_name>
  • game_name is any of the following ``//TODO: game names (not yes implemented)
• PRESS (no args), only handled if game is running
• RELEASE (no args), only handled if game is running
• OPTION args: <mode> <option_name> <value>
  • mode: any of write/read/reset
  • option_name: any of the following
    • progress
    • current_frame - if a projection is active, this will seek to the defined frame of the projection, must not exceed number_of_frames (every pos info gives this argument)
    • point_delay
    • target_frame_time
    • repeat
    • trapeziod_horizontal
    • trapeziod_vertical
  • value only read when using write parameter

responses:

lasershow exec can write to the socket at any time

• ERROR: <e> <details>:
  • e: any of the following; returned if received command couldn't be parsed correctly
    • E2BIG: too many arguments (option read/reset command probably includes value argument)
    • EINVAL: invalid argument (typo in argument or project filename probably has wrong extension)
    • ENOENT: file doesn't exist
    • INVALID_CMD: probably typo in a command
    • OTHER
  • details: if error type supports it, details will be included
• there is no success message
• INFO: <details>
  • details - one of following:
    • OPTION <name> <val>
      • name: name of option being changed; any of:
        • point_delay
        • repeat
        • target_frame_time
        • trapezoid_horizontal
        • trapezoid_vertical
      • val: numeric (float) value of the option
    • STOP
    • PAUSE <val>
      • val: 1 - paused, 0 - not paused
    • PROJECT <filename>
      • filename: filename of the file being projected
    • POS <pos> OF <max>
      • pos: position of coursor in projected file
      • max: size of projected file
• DISPLAY: <text>: client shall display text to the user and hide it when a new command comes or when user sees it
• ALERT: <text>: client shall display text to the user and only hide it and process following commands after user sees the alert

wifi_manager comms

takes following commands

• read: prints out following parameters:

  • wifi_setting: <stealth|wifi|hotspot>
  • wifi_ssid: <SSID>: SSID as returned by iwgetid --raw or iw dev in case hotspot is active
  • mode_raw: <MODE_RAW>: MODE_RAW (0-7) as returned by iwgetid --mode --raw
  • mode: <MODE>: MODE based on MODE_RAW; possible outputs: Auto|Ad-Hoc|Managed|Master|Repeater|Secondary|Monitor|Unknown/bug

• write <stealth|wifi|hotspot>

  • stealth: wifi off
  • wifi: connect to nearby known networks
  • hotspot: create new network, raspberry pi becomes the access point