4 layers78 × 86 mm
SJ-201-R10
MycroftAI/hardware-mycroft-mark-II
Mycroft's Mark II Rpi mechanical, electrical and industrial designs
185 parts113
4 layers45 × 34 mm
Triangle flywheel balancer
RobbyV2/smart_latch_lockA self-closing bike lock built as a clamshell ring. A fixed arc bolts to the housing, a hinged arc swings 180 degrees to meet it, and a worm gearmotor closes the loop around the frame and rim on a button press or a BLE…
- Size
- 45 × 34 mm
- Copper layers
- 4
- Thickness
- 1.59 mm
- Parts
- 70
- Nets
- 64
- Pads
- 284
- Tracks, vias
- 539, 143
- Pours
- 16
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 13 Aug 2026
- Updated
- 14 Aug 2026
Overview
Triangle flywheel balancer is an open-source printed circuit board by RobbyV2, from the RobbyV2/smart_latch_lock repository on GitHub. It is a 4-layer board of 45 × 34 mm with 70 parts on 64 nets, routed with 539 tracks and 143 vias.
It is built around the ESP32-C3-MINI-1-N4, DW01A and MCP73831T-2ACI/OT-HXY, with the XC6220B331MR-G, CL21A106KAYNNNE and CL21A226MAQNNNE among its other parts. Its parts include 22 capacitors, 21 resistors, 7 ICs, 7 connectors and 3 diodes. It belongs with the ESP32 and RISC-V boards of this library.
Main components
12
ESP32-C3-MINI-1-N4
SMD,16.6x13.2mm-40℃~+85℃ -98dBm 20.5dBm 350mA 3V~3.6V 84mA Integrated temperature sensor、Integrated antenna、Built-in watchdog On-board PCB Antenna SPI、UART、I2C、I2S、USB Transceiver SMD,16.6x13.2mm WiFi Modules ROHSEspressif SystemsRF Modules
DW01A
SOT-23-6L-40℃~+85℃ 1 2.5V 300mV~10V 3uA 4.3V Protection IC Support SOT-23-6L Battery Management ROHSPUOLOPBattery Management
MCP73831T-2ACI/OT-HXY
SOT-23-5LBattery ManagementHXY MOSFETXC6220B331MR-G
SOT-25-40℃~+85℃ 1 1A 3.3V 50dB@(1kHz) 655mV@(1A) 6V 8uA Fixed Over Current Protection、Short Circuit Protection、Thermal shutdown、Enable control、Output discharge Positive SOT-25 Voltage Regulators - Linear, Low Drop Out (LDO) Regulators ROHSTorex SemiconductorVoltage Regulators - Linear, Low Drop Out (LDO) Regulators
CL21A106KAYNNNE
080510uF 25V X5R ±10% 0805 Multilayer Ceramic Capacitors MLCC - SMD/SMT ROHSSamsung Electro-MechanicsMultilayer Ceramic Capacitors MLCC - SMD/SMTCL21A226MAQNNNE
080522uF 25V X5R ±20% 0805 Multilayer Ceramic Capacitors MLCC - SMD/SMT ROHSSamsung Electro-MechanicsMultilayer Ceramic Capacitors MLCC - SMD/SMT
KT-0603R
0603-40℃~+85℃ 1.6mm x 0.8mm square LED 1.8V~2.4V 120° 20mA 300mcd 40mW 615nm~630nm 645nm Discrete Diode Red Water Clear 0603 LED Indication - Discrete ROHSHubei KENTO ElecLED Indication - Discrete
CL32A107MPVNNNE
1210100uF 10V X5R ±20% 1210 Multilayer Ceramic Capacitors MLCC - SMD/SMT ROHSSamsung Electro-MechanicsMultilayer Ceramic Capacitors MLCC - SMD/SMT
RC0402FR-0710KL
UncategorisedUnknown maker
0402B102K500NT
04021nF 50V X7R ±10% 0402 Multilayer Ceramic Capacitors MLCC - SMD/SMT ROHSGuangdong Fenghua Advanced Tech (FH)Multilayer Ceramic Capacitors MLCC - SMD/SMT
DFE201610E-1R0M=P2
08061uH 2.7A 3.6A 57mΩ ±20% 0806 Inductors (SMD) ROHSMurataInductors (SMD)
ERJ2RKF6802X
0402-55℃~+155℃ 100mW 68kΩ Thick Film Resistor ±1% ±100ppm/℃ 0402 Chip Resistor - Surface Mount ROHSPanasonicChip Resistor - Surface Mount
README
README.mdFolding-Arc Bike Lock
A self-closing bike lock built as a clamshell ring. A fixed arc bolts to the housing, a hinged arc swings 180 degrees to meet it, and a worm gearmotor closes the loop around the frame and rim on a button press or a BLE command. A spring latch pin seats with power off, a keyed cam lock covers a dead battery, and an ESP32-C3 on a 4-layer PCB runs the state machine.
 |  |
The animation shows one closing cycle: the swing arc starts folded open and sweeps around until it seats in the receiver at the fixed arc tip.
 |  |  |
Read docs/design.md for the mechanism, the torque analysis, and the electronics.
Repository layout
hw/holds the KiCad schematic, the board, the design rules, and the stack manifest.lib/holds the symbols, the footprints, and the 3D models.firmware/holds the PlatformIO project for the ESP32-C3.3d/holds the OpenSCAD housing, the board render script, and the renders.scripts/holds the release script and the validation scripts.fab/holds the fabrication data, written byscripts/release.sh.
Build
pio run -d firmware
openscad -o temp/arc_swing.stl -D 'part="arc_swing"' 3d/housing.scad
python3 3d/build.py
scripts/release.sh hw/triangle_flywheel_balancer.kicad_pcbThe first command builds the firmware, the second renders one housing part (housing_inner, housing_lid, arc_fixed, arc_swing, latch_pin, assembly), the third writes the board renders and the viewer page, and the fourth writes the fabrication tree.
Parts
70| Qty | Value | Footprint | References |
|---|---|---|---|
| 10 | 100nF | triangle_flywheel_balancer:C_0402_1005Metric | C3, C6, C12, C14, C17, C18, C19, C20, C21, C22 |
| 7 | 1k | triangle_flywheel_balancer:R_0402_1005Metric | R4, R7, R10, R14, R17, R18, R19 |
| 4 | 100k | triangle_flywheel_balancer:R_0402_1005Metric | R13, R15, R16, R21 |
| 4 | MountingHole | triangle_flywheel_balancer:MountingHole_3.2mm_M2.5 | H1, H2, H3, H4 |
| 3 | 1uF | triangle_flywheel_balancer:C_0603_1608Metric | C1, C7, C8 |
| 3 | Fiducial | triangle_flywheel_balancer:Fiducial_1mm_Mask2mm | FID1, FID2, FID3 |
| 2 | 10uF | triangle_flywheel_balancer:C_0805_2012Metric | C2, C9 |
| 2 | 22uF | triangle_flywheel_balancer:C_0805_2012Metric | C10, C11 |
| 2 | 4.7uF | triangle_flywheel_balancer:C_0603_1608Metric | C4, C5 |
| 2 | 5.1k | triangle_flywheel_balancer:R_0402_1005Metric | R2, R3 |
| 2 | LED | triangle_flywheel_balancer:LED_0603_1608Metric | D2, D3 |
| 1 | 100uF | triangle_flywheel_balancer:C_1210_3225Metric | C13 |
| 1 | 10k | triangle_flywheel_balancer:R_0402_1005Metric | R1 |
| 1 | 110k | triangle_flywheel_balancer:R_0402_1005Metric | R8 |
| 1 | 15k | triangle_flywheel_balancer:R_0402_1005Metric | R9 |
| 1 | 1nF | triangle_flywheel_balancer:C_0402_1005Metric | C16 |
| 1 | 1uH | triangle_flywheel_balancer:L_Murata_DFE201610P | L1 |
| 1 | 22nF | triangle_flywheel_balancer:C_0402_1005Metric | C15 |
| 1 | 2k | triangle_flywheel_balancer:R_0402_1005Metric | R5 |
| 1 | 330 | triangle_flywheel_balancer:R_0402_1005Metric | R6 |
| 1 | 33k | triangle_flywheel_balancer:R_0402_1005Metric | R11 |
| 1 | 51k | triangle_flywheel_balancer:R_0402_1005Metric | R12 |
| 1 | 68k | triangle_flywheel_balancer:R_0402_1005Metric | R20 |
| 1 | BATTERY | triangle_flywheel_balancer:JST_PH_B2B-PH-K_1x02_P2.00mm_Vertical | J2 |
| 1 | CLOSED | triangle_flywheel_balancer:PinHeader_1x02_P2.54mm_Vertical | J7 |
| 1 | DRV8876PWPR | triangle_flywheel_balancer:HTSSOP-16-1EP_4.4x5mm_P0.65mm_EP3.4x5mm_Mask3x3mm_ThermalVias | U2 |
| 1 | DW01A | triangle_flywheel_balancer:SOT-23-6 | U5 |
| 1 | ESP32-C3-MINI-1-N4 | triangle_flywheel_balancer:ESP32-C3-MINI-1 | U1 |
| 1 | FS8205A | triangle_flywheel_balancer:TSSOP-8_4.4x3mm_P0.65mm | Q1 |
| 1 | LATCH | triangle_flywheel_balancer:PinHeader_1x02_P2.54mm_Vertical | J5 |
| 1 | MCP73831T-2ACI/OT | triangle_flywheel_balancer:SOT-23-5 | U4 |
| 1 | MOTOR | triangle_flywheel_balancer:JST_PH_B2B-PH-K_1x02_P2.00mm_Vertical | J3 |
| 1 | OPEN | triangle_flywheel_balancer:PinHeader_1x02_P2.54mm_Vertical | J6 |
| 1 | SERVO | triangle_flywheel_balancer:PinHeader_1x03_P2.54mm_Vertical | J4 |
| 1 | SW_Push | triangle_flywheel_balancer:SW_Push_1TS009xxxx-xxxx-xxxx_6x6x5mm | S4 |
| 1 | TLV1701AIDBVR | triangle_flywheel_balancer:SOT-23-5 | U3 |
| 1 | TPS61023DRLR | triangle_flywheel_balancer:SOT-563 | U7 |
| 1 | TYPE-C-31-M-12 | triangle_flywheel_balancer:USB_C_Receptacle_HRO_TYPE-C-31-M-12 | J1 |
| 1 | USBLC6-2SC6 | triangle_flywheel_balancer:SOT-23-6 | D1 |
| 1 | XC6220B331MR-G | triangle_flywheel_balancer:SOT-23-5 | U6 |
Questions
How big is the Triangle flywheel balancer PCB?
It measures 45 × 34 mm and has 4 copper layers, 1.59 mm thick.
What parts does the Triangle flywheel balancer use?
70 parts, built around the ESP32-C3-MINI-1-N4, DW01A, MCP73831T-2ACI/OT-HXY and XC6220B331MR-G. 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 Triangle flywheel balancer KiCad files?
From the RobbyV2/smart_latch_lock repository on GitHub, at the commit this page was made from: the board is hw/triangle_flywheel_balancer.kicad_pcb and its schematic hw/triangle_flywheel_balancer.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Triangle flywheel balancer design in my own project?
Its repository states no licence, so its author keeps all rights: ask RobbyV2 before reusing the design.
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