Bill of Materials - joelspadin/NumBLE Wiki

Original URL: https://github.com/joelspadin/NumBLE/wiki/Bill-of-Materials

I have provided part numbers for finding each part on LCSC. These are parts that work, but they are not necessarily the cheapest ones, especially for the generic components like resistors and capacitors.

PCB

Name Value Package Qty. Description LCSC Part#
C1, C2, C7, C8 4.7uF 0603 4 SMD capacitor C307469
C3, C4 12pF 0603 2 SMD Capacitor C38523
R1, R2 5.1k 0603 2 SMD resistor C403509
R3 100k 0603 1 SMD resistor C177329
R5 2.49k 0603 1 SMD resistor C203449
R6 3.9k 0603 1 SMD resistor C25997
R7 100 0603 1 SMD resistor C25201
L1 10uH 0603 1 SMD inductor C127280
D1-12 BAT54C SOT-23 12 Dual signal Schottky diode C37704
D13 Orange LED 0603 1 SMD LED (~2V) C233192
D14 Red LED 0603 1 SMD LED (1.7-1.8V) C241893
D15 1N5819 SOD-323 1 Schottky diode C489147
F1 ASMD1206-200 0805 1 PTC resettable fuse C135342
Q1 AO3407 SOT-23 1 P-MOSFET C382316
Y1 32.768kHz 3215 1 SMD crystal C48615
U1 USBLC6-2SC6 SOT-23-6 1 USB ESD protection C7519
U3 MCP73831-2-OT SOT-23-5 1 Li-Ion/Li-Po charger C424093
U4 E73-2G4M08S1C 1 nRF52840 module C356849
J1 HRO TYPE-C-31-M-12 1 USB connector C165948
J3 JST S2B-PH-SM4-TB 1 Battery connector C295747
SW1 JS202011JCQN 1 DPDT slide switch C221665
SW2 KSC721J LFS 1 SPST tactile switch C2799444

The value of R5 is chosen for a battery capacity of at least 400 mAh. Use a 5k resistor for 200-400 mAh or a 10k resistor for 100-200 mAh.

The value of R6 adjusts the brightness of the charging status LED. For the LED I chose, 1k was very bright, and 3.9k resulted in a reasonable brightness.

If you want hot-swap, you can use Mill-Max 0305-2-15-80-47-80-10-0 sockets. You will need two sockets per switch. (Buy extras. They are tiny, and you will probably lose a few.)

If you want to use a rotary encoder, I recommend looking for one where neither A or B terminal is connected to ground while at a detent, such as the Bourns PEC11R and PEC11L series. Otherwise there will be a constant leakage current at some encoder positions, which will reduce battery life.

Fuel Gauge (Optional)

The following parts are for the fuel gauge IC. This is optional and cannot be soldered using a soldering iron. You will need to use a stencil, solder paste, and a hot air gun or reflow oven. If you omit these parts, the battery charge status will be less accurate, and it will report 100% charge while connected to USB, regardless of the actual state of charge.

Name Value Package Qty. Description LCSC Part#
C5 0.47uF 0603 1 SMD capacitor C105526
C6 0.1uF 0603 1 SMD capacitor C66501
R4 LVT08R0050FER 0805 1 Ohmite LVT08 sense resistor C2479993
U2 MAX17260SETD+ TDFN-14 1 Fuel gauge C350946

MAX17263LETD+ (LCSC C1519513) can be substituted for U2. It has very slightly higher power consumption, but otherwise functions identically.

Other Hardware

As above, the links here are to parts that work, but you will likely be able to find cheaper alternatives.

Description Qty Link
MX style switches 21-24
2U plate mount stabilizers 0-3
Li-Po battery, maximum dimensions 39 x 70 x 6 mm 1 Adafruit
Neodymium magnet, 1/16" thick, 3/16" diameter 10-18 McMaster-Carr
Heat set insert, M3, 4 mm outer diameter, 3-4 mm length 4 Adafruit
M3 bolt, 4-7 mm length, head ≤ 5.5 mm diameter and ≤ 3.5 mm height 4 McMaster-Carr
6 mm bumpons 4 Amazon
1.6 mm plate (any material) 1 DXF File
Case top (3D printed) 1 STL File
Case bottom (3D printed) 1 STL File
Super glue, epoxy, or other adhesive

The 21-key layout uses 3 stabilizers. The 22-key layout uses 2. The 24-key layout does not use any.

Depending on the weight of your plate material and case material, you may not need to use all 18 magnets to securely hold the case together.