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Stringent is a real, open-source Arduino wall plotter—not a $15 product you can buy. Fredrik Stridsman published the crossed-string project on Hackster.io on June 23, 2018. It reels two threads from stepper-motor spools to position a pen on a whiteboard or other vertical surface, with drawings loaded from an SD card and setup controlled by an infrared remote. The “$15” label is a historical low-cost design target, not a complete, verified 2026 bill of materials.
Stringent in one minute
Stringent is a compact, suspended pen plotter. Two upper anchor points hold crossed threads that run down to a mobile plotter body. Each thread is wound on a motorized spool. By reeling the left and right threads in different amounts, an Arduino changes the body’s horizontal and vertical position and traces line segments from an SVG file. A small servo lifts the pen or changes its contact with the board.
The project’s files—code, documentation, CAD and sample designs—are published in the author’s MIT-licensed GitHub repository. The original project page is the authoritative source for its build history and limitations (Hackster).
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- Applicable system(s):XP/win7/win8/win10 ，Mac is not compatible. Supported Software: Bachin Draw, Please contact seller for support with software installation if necessary. NOTE: It is a plotter, not a printer.
- Imitation human writing: A drawing robot that can move a pen or other instrument to draw/write digital artworks on the flat surface like a human, no matter Chinese or English, etc.Support Over 100 Fonts, You Can Customize Your Fonts Too. You have to make fonts in the first place.
- Colorful layer painting: It can draw the pictures with many different colors. Good for making the posters.
- Open source: If you want to design your own XYZ plotter, the interface documentation can be provided (the detailed info., as below in the description) .Better for Repeat Jobs or Your Small Business
- Cross-disciplinary innovation :A research tool for creators, DIY enthusiasts, students, teachers, automation researchers, etc.p
Why the crossed strings matter
The arrangement is related in principle to cable-driven or gondola-style plotters, but Stringent is not a Maslow CNC and does not share its mechanical or software architecture. The two threads cross near the upper part of the chassis. That routing helps keep the plotter against the wall while allowing the motors and pen to travel as one small unit.
The trade-off is rotation. A cable system resists translation better than twisting around its vertical axis, so the frame needs restraints—such as the zip ties used in the project—to prevent unwanted yaw. Anchors must also hold the thread close to the wall; if the line stands too far off the surface, pen pressure becomes unreliable.
What you need
Electronics
- Arduino Uno
- Two 28BYJ-48 stepper motors with driver boards
- TSOP4838-compatible infrared receiver and remote
- SPI micro-SD card reader and card
- SG90 micro-servo
- Appropriate regulated power, wiring and connectors
Mechanical parts and tools
- Plotter frame, spools, pen holder and fasteners
- Sewing thread or similar cord
- Wall anchors (suction cups can work on suitable whiteboards)
- Pen or marker
- Arduino IDE, soldering iron and a way to fabricate the frame
The published list is not a complete BOM. It does not fully price or specify the power system, remote, card, pen, thread, anchors, cables, fasteners, shipping or consumables. The author also demonstrated a “MacGyver” version made from tie wire, duct strap, zip ties, gaffer tape and a milk-container cap, so a 3D printer is useful but not mandatory.
Six iterations, not one fixed machine
| Version | Main change | Result |
|---|---|---|
| 1 | Hard-coded drawing, fixed one-metre setup and large spools | Simple proof of concept, but changing artwork required reflashing and the offset pen wobbled. |
| 2 | Smaller, higher spools; SD storage; IR remote; variable anchor spacing | More practical setup and author-reported plot widths up to about 2.5 m. |
| 3 | Arduino shield and battery-level watchdog | Cleaner electronics; wired power was still preferred for long plots. |
| 4 | More polished construction | Improved presentation rather than a major kinematic change. |
| 5 | Improvised materials | Showed that specialized fabrication equipment was optional. |
| 6 | Smaller body, analog pins for servo and IR, pen moved independently | Better serial-debug access and a smaller footprint, but more pen wobble and worse accuracy. |
These are the author’s reported iterations, not independently measured product generations.
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Rank #2
- The plotter is your all-in-one creative sidekick: From getting those ideas out in writing a thank-you letter/holidy card or drawing a complex picture with multiple colors, it's perfect for it all. Hundreds of fonts are provided or you can imitate your own fonts (You need create your own custom fonts, we can provide step-by-step guidance to help you.)
- No assembly needed, start to use after several minutes set-up: The plotter is designed for instant creativity. Unbox, set up, power on, and start writing or drawing. Perfect for hassle-free, plug-and-play convenience!
- User-friendly software provided: compatible with Windows 7/8/10/11, macOS, and Linux OS. Perfect for handwriting imitation to write letter, cards or invitation letter, draw and learn programming.
- Extensive file format supported, including JPG, JPEG, PNG, BMP, SVG, etc.
- High-Speed Performance: Writes up to 15,000mm per minute, delivering fast and efficient results for all your projects. And you adjust the speed according to your needs.
A sensible build and bring-up sequence
Do not assemble everything at once. The project recommends testing each subsystem independently:
- Load the
IRRecvDumpexample from the IRRemote library and verify that the receiver sees your remote. - Run the Servo library’s
Sweepexample. - Test the SD reader with the Arduino SD-library examples.
- Test each stepper with the Stepper-library examples.
- Flash the Stringent program and connect the complete electronics.
- Power up and confirm the servo’s startup sweep.
- Use the remote to identify left and right motors.
- Verify that
REEL_INactually pulls the intended thread inward. Reverse connector order or software pin order if it does not. - Only then fabricate, hang and calibrate the finished plotter.
Pins 0 and 1 are serial TX/RX. Hardware attached there can interfere with uploading, so disconnect it while programming unless your shield or wiring makes those connections removable. Do not assume a pinout from a repost; use the schematic and code in the repository.
Preparing artwork
Stock Stringent is not a general SVG renderer. The documented 2018 workflow uses Inkscape:
- Create the artwork.
- Choose Path → Object to Path.
- Press F2 to select the path-editing tool and select the relevant paths and nodes.
- Use Extensions → Modify Path → Flatten Beziers to turn curves into line segments.
- Save as Inkscape SVG.
- Place numbered files such as
1.svg,2.svgand3.svgin the SD card’s top-level directory.
Current Inkscape releases may rename or relocate menu entries. The important requirements are line-based paths and the SVG dialect the firmware expects. Complex features, unsupported metadata and excessive decimal precision can fail. The supplied simulator compiles the plotting code for macOS or Linux, visualizes the generated pin-state timing and estimates plot duration. It became especially valuable after a long plot failed near completion because an SVG number contained too many decimal places.
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Rank #3
- [Offline Function] With a built-in flash memory chip on the mainboard, the device automatically saves your last written content. This allows you to use it independently, without needing to keep it connected to a computer.
- [Pre-assemble] Ready to use right out of the box, no assembly required.
- [High-end design] A stronger cable tie secures the wires neatly, preventing them from getting pinched or stuck, effectively protecting them. No cables to be organized.
- [Less noise & less heat] Higher-performance motor driver chip provides quieter operation and lower heat generation.
- [Reliable & durable] xdraw pen plotter is valuable wherever precision, repeatability, and a “handwritten” or “hand-drawn” output is needed.
Calibrating on the wall
- Attach the left and right thread ends to upper anchor points.
- Use the remote to move the plotter and mark position A.
- Move across to position B and mark it.
- Use the thread’s marked 20 cm intervals instead of measuring loose thread manually.
- Determine anchor spacing by counting left-stepper movement while travelling from A to B.
- Let the plotter establish its coordinate system.
- Select a numbered drawing with the remote and run it below and between the anchors.
The source illustrates the geometry; copy its diagram and labels rather than inventing a calibration formula. Start with a small test drawing. The author’s practical rule is “Hang high, print low.” High anchors and a lower drawing region reduce the tension extremes that cause stalls.
Accuracy and reliability: the honest assessment
Stringent is an inventive maker experiment, not a precision commercial plotter. Its controller is open loop: there are no encoders, so after a missed step the Arduino continues issuing commands while believing the plotter is still at the calculated position.
- Weak actuators: 28BYJ-48 motors are inexpensive but have limited pulling force and speed.
- Geometry-dependent accuracy: anchor spacing, plot location, thread routing and pen pressure all change the load.
- Rotation: crossed strings improve positioning but need anti-twist restraint.
- Pen mechanics: the later moving-pen experiment reduced the frame size but introduced visible wobble.
- Power and heat: the author reported running nominally 5 V motors at 5–9 V in one build, with heat. That is not a recommended operating range; follow the specifications for your exact motor and driver and monitor temperature.
- Recovery: after a stall, stop the plot, correct the mechanical cause and recalibrate. The machine cannot discover its lost position by itself.
Reduce speed, use smaller spools, minimize pen friction, keep the frame close to the wall, limit the first plots in width and test difficult sections before committing to a long run. Wide or high plots are especially demanding.
Is it really a $15 build in 2026?
There is no responsible current answer of “yes” without an itemized, dated BOM. Bare commodity electronics may still be inexpensive, but a complete build also needs power, mounting, thread, pen hardware, fabrication and shipping. Add stronger motors, a modern controller, regulated power or feedback and it becomes a different, substantially more expensive design. The title should be read as historical cost framing: the author says he did not meet his original goal of getting below $10.
Rank #4
- All-in-one Design, Pre-assembled, Use Out of Box - This feature ensures that the drawing robot comes fully assembled and ready to use straight out of the box, allowing artists to start their projects immediately without any setup hassle.
- Advanced CoreXY Motion Structure - The motion structure utilizes a CoreXY design, providing enhanced precision and stability for all your drawing and engraving needs.
- Support Stand-alone Command Line Interface (CLI) and Available iDraw Python API - This feature provides flexibility for advanced users, enabling control through a command line interface and offering an API for integration with custom Python scripts, enhancing automation and customization.
- Versatile Base Plate Design - The redesigned base plate features various size positioning from A5 to A3, allowing artists to easily locate home points and drawing sizes.
- Support PremiumUltra Scriptalizer - This feature introduces random font variation with ease, giving artworks a unique and dynamic appearance by automatically varying fonts in each project
Who should build it?
Stringent suits experienced Arduino makers, robotics students, educators, whiteboard-art enthusiasts and anyone curious about cable-driven kinematics. It is a poor fit for unattended business signage, precision technical drawing or anyone expecting a kit, guaranteed wiring table, current firmware support or instant operation.
Alternatives and sensible modernization
A conventional XY pen plotter is easier to calibrate on a fixed flat surface. Polargraph-style machines offer a related cable approach and may have more mature current software. Commercial wall plotters cost far more but can provide stronger mechanics, support and feedback. Hektor is useful historical context and an inspiration cited by the author, but it is a separate project (Hektor).
A modern Stringent derivative could retain the crossed strings while using a more capable controller, USB/Wi-Fi control, computer-side path conversion, stronger specified actuators, consistent reels, regulated monitored power and encoders or homing feedback. Those are design opportunities—not features of the published build. The original remains valuable precisely because it exposes the mechanics and invites experimentation.
Frequently Asked Questions
Can I buy Stringent as a $15 machine?
No. Stringent is an open-source project, not a finished product. The $15 figure is a historical project label and does not include a complete current BOM.
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Does Stringent draw arbitrary SVG files?
No. Its documented workflow expects simplified, line-based Inkscape SVG files. Convert objects to paths, flatten curves and test the file in the simulator first.
What happens if a motor skips?
The controller has no encoders and will not know. Stop the plot, fix tension, friction or speed problems, then recalibrate before restarting.
The Bottom Line
Build Stringent for the learning value: it is a clever, inexpensive crossed-string plotter with public source files and a large potential drawing area. Do not choose it for guaranteed precision, plug-and-play assembly or a literal $15 delivered cost. In 2026, it is best approached as a reproducible open-hardware experiment—or as a starting point for a better-powered, better-calibrated derivative.
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