Riyu-D1/PCB-KeychainA simple yet cool and functional pcb keychain. Exactly what it sounds like!
Keychain is an open-source printed circuit board by Riyu-D1, from the Riyu-D1/PCB-Keychain repository on GitHub. It is a 2-layer board of 68 × 38 mm with 19 parts on 17 nets, routed with 1,643 tracks and 23 vias.
It is built around the TP4056, SK6812MINI-E and SS14. Its parts include 6 capacitors, 5 diodes, 4 connectors, 1 resistor and 1 IC.
A simple yet cool and functional pcb keychain. Exactly what it sounds like!
A small keychain about the size of a 2.36" colour e-ink screen. The screen sits flat on the front of the board, and there are four little RGB LEDs, two on each side, so it lights up whichever way it's hanging.
I kept it simple on purpose. The brains are an ESP32-C3 SuperMini, a tiny dev board that already has USB-C, a regulator and a boot button on it, so I just solder it onto the back with headers. The e-ink screen comes on Waveshare's driver board and plugs into an 8-pin header at the top.
It runs off a small LiPo. A TP4056 charges it from the SuperMini's USB-C, a slide switch turns it on and off, and a diode lets the battery power the board when it's unplugged. Because e-ink keeps its picture with no power, the battery lasts a long time.
Full list in bom.csv.
Cost: about $28.35 USD for one keychain (single-unit prices from LCSC, Waveshare, Tindie and Adafruit, not counting the PCB, shipping or LCSC minimum order quantities).
KiCad project is in kicad/. Open keychain.kicad_pro.
| Qty | Value | Footprint | References |
|---|---|---|---|
| 4 | 100nF | C_0603_1608Metric | C3, C4, C5, C6 |
| 4 | SK6812MINI | LED_SK6812MINI_PLCC4_3.5x3.5mm_P1.75mm | D1, D2, D3, D4 |
| 2 | 10uF | C_0603_1608Metric | C1, C2 |
| 1 | 1.2k | R_0603_1608Metric | R1 |
| 1 | BATTERY | JST_PH_B2B-PH-K_1x02_P2.00mm_Vertical | J4 |
| 1 | EPAPER | PinHeader_1x08_P2.54mm_Vertical | J1 |
| 1 | MountingHole_4.5mm | MountingHole_4.5mm | H1 |
| 1 | SS14 | D_SMA | D5 |
| 1 | SW_SPDT | SW_SPDT_PCM12 | SW1 |
| 1 | SuperMini-L | PinHeader_1x08_P2.54mm_Vertical | J2 |
| 1 | SuperMini-R | PinHeader_1x08_P2.54mm_Vertical | J3 |
| 1 | TP4056 | SOIC-8-1EP_3.9x4.9mm_P1.27mm_EP2.29x3mm | U1 |
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It measures 68 × 38 mm and has 2 copper layers, 1.6 mm thick.
19 parts, built around the TP4056, SK6812MINI-E and SS14. 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.
From the Riyu-D1/PCB-Keychain repository on GitHub, at the commit this page was made from: the board is kicad/keychain.kicad_pcb and its schematic kicad/keychain.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Its repository states no licence, so its author keeps all rights: ask Riyu-D1 before reusing the design.