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YOU CAN BUILD THE MACHINE THAT GROWS A LASER CRYSTAL ON YOUR BENCH

About a week of slow, controlled cooling grows a large, optically clear laser crystal, and the machine that does it is yours to build.

by Les Wright

FULL CAD BOM FIRMWARE DOCS

ScienceOpen-hardware

Built withArduino

difficulty
●●●●○
time
a weekend for the machine, a week watching it grow
license
Apache-2.0
repo
repo INACTIVE (LAST PUSH DECEMBER 2024)36 stars

WHAT YOU’LL NEED

Videos
1
Jump to section

COMPAREE VERDICT

This is a rotating crystalliser that grows KDP (potassium dihydrogen phosphate), a nonlinear optic crystal used to convert laser light to shorter wavelengths. A seed crystal sits on a platform in a supersaturated solution; a stepper on the lid rotates the platform back and forth while the firmware lowers the temperature slowly over about a week. A DS18B20 probe reads the temperature, an SSD1306 OLED shows the status, and a laboratory hot plate is switched on and off through a solid-state relay. Two Arduinos split the work: one runs the stepper, one the temperature control. The repo, published under Apache 2.0, has gerbers for the controller board, LightBurn files for the acrylic cage, both Arduino sketches and Python for logging. The hard part is that the bill of materials section is empty, so you work out the parts list from the board files and the video. The repository calls itself a work in progress, and the roughly one-week figure is the maker's own run, not a specification. If you know what a DS18B20 and AccelStepper are and want a desktop crystal-growing experiment, this is exactly what you need. If you expect a turnkey parts list, you will spend your first evening with the gerbers and the video.

GOOD TO KNOW

  • —Gerber files for the controller board (November 2024 revision) are present.
  • —LightBurn files for the laser-cut acrylic cage and lid are present.
  • —Arduino firmware for both the rotator and the temperature controller is present.
  • —Python scripts for logging and plotting are present.
  • —The bill of materials section in the README is empty — you work from the board files and the video.
  • —The repository describes itself as a work in progress.
  • —Apache 2.0 licence, no commercial restrictions.

Parts to buy

11 items

From our check of the build. Exact quantities and part numbers are in the creator’s BOM.

  • PCB from the gerbersfrom the repo files
  • Laser-cut acrylicFind
  • Two ArduinosFind
  • DRV8825 stepper driver and stepper motorFind
  • DS18B20 temperature probeFind
  • SSD1306 OLEDFind
  • Solid-state relayFind
  • 12 V power supplyFind
  • Laboratory hot plateFind
  • BeakerFind
  • Potassium dihydrogen phosphateFind

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Can I build this?

Printnothing required — laser-cut acrylic from LightBurn files
BuyPCB from the gerbers, laser-cut acrylic, two Arduinos, DRV8825 stepper driver and stepper motor, DS18B20 temperature probe, SSD1306 OLED, solid-state relay, a 12 V power supply, a laboratory hot plate, a beaker, and potassium dihydrogen phosphate
Toolssoldering iron, access to a PCB fab house and a laser cutter, Arduino IDE, Python
Skillsintermediate electronics and firmware, chemistry knowledge helpful but not required — the hard part is sourcing components from incomplete documentation
Timea weekend to build the machine, then about a week watching the crystal grow
CostBoard fab, laser-cut acrylic, two Arduinos, the stepper, a solid-state relay and a lab hot plate; the repo gives no total, so price the parts yourself.
SafetyMains voltage if you use a mains-powered heater. Relay-switched heating means no PWM, but you are still switching mains. KDP itself is low hazard but you are working with hot saturated solutions. Standard lab care.

This build involves mains voltage — for adults comfortable with electrical work only.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

Videos

Creator’s build video

Primary video showing the machine in operation and the crystal growth process.

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Gallery

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Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Watch the primary video to see the machine running and the crystal forming. (This is where you will extract the missing parts list.)
  2. 2.Open the gerber files and identify every component on the controller board.(The BOM section is empty — this step is not optional.)
  3. 3.Send the gerbers to a PCB fab and the LightBurn files to a laser cutter.(You need both before you can assemble anything.)
  4. 4.Flash the Arduino firmware to the rotator and temperature controller.(Two separate microcontrollers, two separate sketches.)

Resources

Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.

KNOWN ISSUES

  • The bill of materials section is empty. You will spend time reverse-engineering the parts list from the board files and the video before you can order anything.
  • The repository describes itself as a work in progress. The design works but expect missing documentation and unfinished sections.
  • The roughly one-week growth time is the maker's figure from his own run, not a specification. Your results will vary with temperature control and solution preparation.
  • The heater is relay-switched, not PWM-modulated. If you are used to PID-controlled heating, this is a different approach and you need to understand how the firmware handles it.
  • You need access to both a PCB fab house and a laser cutter. If you do not already have those in your workflow, that is two new supplier relationships to establish.

What is KDP used for?

Potassium dihydrogen phosphate is a nonlinear optic crystal. It converts laser light from one wavelength to another — typically infrared into visible or ultraviolet. It is the workhorse of frequency-doubling and sum-frequency generation.

Can I grow other crystals with this machine?

Yes, in principle. The rotation and temperature control are general-purpose. You would need to adapt the solution chemistry and the temperature profile to whatever crystal you are growing.

How do I get the parts list if the BOM is empty?

Open the gerber files in a PCB viewer and identify every component by its footprint and reference designator. Cross-reference with the video to see what the maker actually used. It is not fast but it is not mysterious.

Why is the heater relay-switched instead of PWM?

The heater is a simple laboratory hot plate switched by a solid-state relay. The maker says the hot plate cannot be PWM-controlled, and PID seemed like overkill, so the firmware uses simple on/off (bang-bang) control around the target temperature.

Community builds

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Discussion1

FROM THE COMPAREE TEAM

The roughly one-week growth time is the maker's own figure from his run. What would you change in the temperature profile to speed that up, and what would you risk?

CompareeTEAM1mo agoedited

Practical notes from our verification: the gerber files are from a November 2024 board revision, the LightBurn files are present for the acrylic cage and lid, and the Arduino firmware is split across two sketches — one for the rotator, one for the temperature controller. The hard blocker is that the bill of materials section in the README is empty, so you are working backwards from the board files and the video to figure out what to buy. The repository describes itself as a work in progress, which is honest — the design clearly works but the documentation is not finished. If you are comfortable reverse-engineering a parts list from gerbers, this is a weekend project. If you expected a turnkey build, plan for an extra evening of forensics before you order anything. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.

Les Wright

Les Wright publishes experiments in optics, lasers, and crystal growth. The rotating crystalliser came out of a need to grow KDP for his own laser work, and he published the design under Apache 2.0 so others could do the same.

GitHub

Star the project on GitHub

DISCLAIMER

  • Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
  • Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
  • Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
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