2 layers33.9 × 42.5 mm
Kicad sensor on side
evaEko/knife_whetting_level
Firmware for a knife-sharpening angle guide — nRF52840, BNO085 IMU, SSD1306 OLED
8 parts30
2 layers26.5 × 42.5 mm
Kicad sensor on side big display
evaEko/knife_whetting_level30Firmware for a knife-sharpening angle guide — nRF52840, BNO085 IMU, SSD1306 OLED
- Size
- 26.5 × 42.5 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 12
- Nets
- 32
- Pads
- 63
- Tracks, vias
- 64, 0
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 21 Apr 2026
- Updated
- 5 Sep 2026
Overview
Kicad sensor on side big display is an open-source printed circuit board by evaEko, from the evaEko/knife_whetting_level repository on GitHub. It is a 2-layer board of 26.5 × 42.5 mm with 12 parts on 32 nets, routed with 64 tracks and 0 vias.
Its parts include 3 ICs and 2 switches. It belongs with the lEDs and displays and sensors and measurement boards and the nRF52 and nRF5x boards of this library.
README
README.mdKnife Level BLUNT
A small digital level for knife sharpening. Measures blade surface inclination in real time, displays the angle, and alerts you when you drift from your target sharpening angle.
Built on MicroPython running on an nRF52840 microcontroller.
Here are some vids:
Commercial use and resale are not permitted.
License
- Software code, documentation, images, and hardware design files: CC BY-NC 4.0
- Third-party subcomponents may use their own license where noted (for example,
kicad/nice-nano-kicad/)
Third-party notices
kicad/nice-nano-kicad/is a third-party nice!nano symbol/footprint library bundled with this project.- The bundled library declares
GNU GPLv3inkicad/nice-nano-kicad/README.md; keep that notice and attribution when redistributing those files.
Disclaimer: This project is provided as-is, without warranty of any kind. The author is not liable for any damage, injury, or loss arising from the use, misuse, or inability to use this project or any hardware built from it.
Getting Started
- Assemble the hardware
- Flash the firmware
- Optionally install the Android companion app from the
knife_level_android_apkworkflow artifact
If impatient, go over to Quick Start.
Known Issues
- Android app rescan after restart — if you power-cycle the level, the Android app will not reconnect automatically; open the app and scan again.
- Lifted detection is experimental — the feature that detects when the blade leaves the stone is not reliable and may produce false positives or miss lift events; treat alerts that depend on it as best-effort.
Acknowledgements
Thanks to jkorte-dev for publishing the nRF52840 SuperMini/Nice!Nano MicroPython board definitions and UF2 builds used as a flashing base.
Development was assisted by Claude (Anthropic).
Features
- Live sharpening angle — displays current blade surface inclination in real time on the OLED, rounded to nearest 0.5° with one decimal place
- Rotation-invariant measurement — the sensor attaches to the blade with a magnet and can spin freely on the blade face; the reading reports the correct blade angle regardless of how the sensor is rotated on the surface
- Session calibration — set the current surface as zero from the on-device settings menu or the Android app
- Angle setting — set the current angle as the sharpening angle
- Visual alert — display inverts when you drift more than the configured threshold from the target angle; both 0° and 180° orientations are treated as equivalent (knife flipped upside-down is the same angle); threshold supports decimal values (e.g. 0.5°)
- Preset angle profiles — define named knives and their angles in
angles.csv; select them on-device with the top button, with optional restore of the last selected preset after reboot - Calibration + presets are independent — calibrate once to set your physical reference point (zero), then switch between knife presets freely; each preset angle is always displayed relative to the calibration, never compounding
- Bluetooth companion app — configure display/behavior settings over BLE, calibrate from the phone, manage preset angles with CRUD operations, and back up/restore presets plus app-exposed settings after reflashing
Parts
12| Qty | Value | Footprint | References |
|---|---|---|---|
| 2 | Conn_01x01 | Connector_Wire:SolderWire-0.1sqmm_1x01_D0.4mm_OD1mm | BAT-1, BAT+1 |
| 2 | SW_Push | Button_Switch_SMD:SW_Push_1P1T_NO_CK_KSC6xxG | SW1, SW2 |
| 1 | GY-BNO08X | Connector_PinHeader_2.54mm:PinHeader_1x10_P2.54mm_Vertical | U2 |
| 1 | SSD1306_OLED_042 | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical | U3 |
| 1 | SW_SPDT | Button_Switch_SMD:SW_SPDT_Shouhan_MSK12C02 | SW_POWER1 |
| 1 | nice_nano | nice_nano:nice_nano_with_bat_pins | U1 |
The 8 most common of 12 parts.
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Questions
How big is the Kicad sensor on side big display PCB?
It measures 26.5 × 42.5 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Kicad sensor on side big display use?
12 parts. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Kicad sensor on side big display KiCad files?
From the evaEko/knife_whetting_level repository on GitHub, at the commit this page was made from: the board is kicad/kicad_sensor_on_side_big_display.kicad_pcb and its schematic kicad/kicad.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Kicad sensor on side big display design in my own project?
Its repository states no licence, so its author keeps all rights: ask evaEko before reusing the design.