2 layers32 × 43 mm
SZSERVOEXTENDER
gmaxdragon/Modular-Pi-Hat
I made a massive PCB which is a PI Hat for my robotic arm. I really wanted to streamline everything and shrink it down and make it more reliable so I made this. It's really cool.
4 parts1
2 layers65 × 56 mm
I made a massive PCB which is a PI Hat for my robotic arm. I really wanted to streamline everything and shrink it down and make it more reliable so I made this. It's really cool.
- Size
- 65 × 56 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 41
- Nets
- 79
- Pads
- 228
- Tracks, vias
- 1,448, 66
- Pours
- 3
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 7 Oct 2026
- Updated
- 25 Oct 2026
Overview
Test1 is an open-source printed circuit board by gmaxdragon, from the gmaxdragon/Modular-Pi-Hat repository on GitHub. It is a 2-layer board of 65 × 56 mm with 41 parts on 79 nets, routed with 1,448 tracks and 66 vias.
It is built around the ESP32-S3-WROOM-1-N8R8 and AP2112K-3.3. Its parts include 13 resistors, 12 connectors, 6 capacitors, 2 ICs and 1 diode. It belongs with the ESP32 boards of this library.
Main components
2
ESP32-S3-WROOM-1-N8R8
SMD,25.5x18mm-104.5dBm -40℃~+65℃ 2.4GHz 20.5dBm 330mA 3V~3.6V 97mA Bluetooth5.0 ESP32-S3R8 On-board PCB Antenna UART、SPI、I2C、GPIO、I2S、USB SMD,25.5x18mm WiFi Modules ROHSEspressif SystemsWiFi Modules
AP2112K-3.3
SOT253.3V 600mA CMOS Low Dropout Linear Regulator with EnableDiodes IncorporatedUncategorised
README
README.mdModular PI HAT
24 October 2026 technical audit: Both the main KiCad project and servo-extender KiCad project, plus their separate Gerber/drill packages, are present in this repository. These are unassembled design files. The archived $79.05 figure includes $30 estimated shipping, excludes tax and unlisted material, and is not a live manufacturing quote. The selected 2A servo fuse, 3.3V regulator thermal/load margin, USB connector land pattern, stacking/header clearances and 4-wire extender cable still require physical review before energizing the robot. The OLED pin sequence differs from J10 and must be individually remapped, never plugged directly. Detailed engineering release gates. This note is technical and leaves the owner's original project narrative intact.
What I made
I made a massive PCB which is a PI Hat for my robotic arm. I really wanted to streamline everything and shrink it down and make it more reliable so I made this. It's really cool.
What it does
The big board is a massive PI Hat that can control servos, attach to sensors, and connect to the mini board which is connected by a big cable to the main board on screw terminals and it controls 2 servos for the wrist and gripper.
Why I made it
I made it because I was having a ton of difficulties making everything move correctly and everything was all over the place. It's way simpler, easy to use, and reliable.
My work and what I learned
I personally worked on the schematics and routing and basically, I added all the components, added power symbols, added net labels, and multiple more stuff and routed and adjusted the whole PCB. I worked through a lot of problems such as the ERCs not budging, a ton of short circuits reported in the DRC and a ton of more annoying problems. However, I learned the whole flow of how to make a schematic and a PCB and it feels really good now.
Current status
Currently, the whole board is finished. The schematics, the routing, and testing is all good now. Nothing has been made as of now and I need to test it out and solder it once it comes.
Help and sources
I used AI a ton in order to guide me with making the full thing and giving me instructions on how to fix some errors. Mostly, I used the ERC and DRC a ton as it's extremely helpful for me and it pinpoints where all the errors are and I used the help of some friends in school to tell me what to do. Honestly, AI helped with making the schematics and telling me what parts I need and researching meanwhile I did the work, it helped me with organizing and kicking off routing the board, it helped me when there was annoying footprint issues, and a ton of error fixing and instructions.
Journal note
Hey, I accidentally added Week 3 one of the journal entries here, don't mind it please. I couldn't find a way to remove it.
Bill of materials
PCB fabrication is $4.00 per board. This table includes one main PCB and one servo-extender PCB. Shipping remains the existing $30.00 estimate.
| Item | Qty | Supplier | Cost/item (USD) | Total cost (USD) | Link |
|---|---|---|---|---|---|
| ESP32-S3-WROOM-1-N8R8 module, 8MB flash + 8MB PSRAM | 1 | Mouser | $6.28 | $6.28 | Part |
| AP2112K-3.3 3.3 V LDO regulator | 1 | DigiKey | $0.28 | $0.28 | Part |
| 40-pin extra-tall 2x20 female stacking header | 1 | DigiKey | $2.95 | $2.95 | Part |
| 4-way 5.08 mm Phoenix screw terminal | 2 | DigiKey | $2.28 | $4.56 | Part |
| 2-way 5.08 mm Phoenix screw terminal | 1 | DigiKey | $1.16 | $1.16 | Part |
| Breakaway 0.1 inch male pin header strips, 10-pack | 1 | DigiKey | $4.95 | $4.95 | Part |
| USB-C USB2.0 receptacle | 1 | DigiKey | $0.80 | $0.80 | Part |
| 470 uF 10 V through-hole capacitor | 1 | DigiKey | $0.71 | $0.71 | Part |
| 100 uF 25 V through-hole capacitor | 1 | DigiKey | $0.87 | $0.87 | Part |
| 22 uF 10 V 1206 ceramic capacitor | 1 | DigiKey | $0.47 | $0.47 | Part |
| 1 uF 50 V 0805 ceramic capacitor | 3 | DigiKey | $0.18 | $0.54 | Part |
| 100 nF 50 V 0805 ceramic capacitor | 1 | DigiKey | $0.10 | $0.10 | Part |
| 10k 1 percent 0805 resistor | 4 | DigiKey | $0.10 | $0.40 | Part |
| 5.1k 1 percent 0805 resistor | 2 | DigiKey | $0.10 | $0.20 | Part |
| 22 ohm 1 percent 0805 resistor | 2 | DigiKey | $0.10 | $0.20 | Part |
| 1k 1 percent 0805 resistor | 1 | DigiKey | $0.10 | $0.10 | Part |
| 75k 1 percent 0805 resistor | 1 | DigiKey | $0.10 | $0.10 | Part |
| 100k 1 percent 0805 resistor | 1 | DigiKey | $0.11 | $0.11 | Part |
| 4.7k 1 percent 0805 resistor | 2 | DigiKey | $0.10 | $0.20 | Part |
| Green 0805 LED | 1 | DigiKey | $0.19 | $0.19 | Part |
| SPST SMD tactile switch | 2 | DigiKey | $0.21 | $0.42 | Part |
| Keystone mini blade through-hole fuse holder | 1 | DigiKey | $1.31 | $1.31 | Part |
| Littelfuse MINI 297 2A 32V blade fuse, selected for prototype | 1 | DigiKey | $0.39 | $0.39 | Part |
| 0.91 inch white 128x32 SSD1306 I2C OLED breakout, DFRobot DFR0648 | 1 | DigiKey | $9.90 | $9.90 | Part |
| 4-position 2.54mm Samtec OLED female socket | 1 | DigiKey | $1.11 | $1.11 | Part |
| 6 inch male-to-female jumper cable kit, 20 wires, for OLED J10 pin-order correction | 1 | DigiKey | $2.75 | $2.75 | Part |
| Main PCB fabrication, 1 bare board | 1 | JLCPCB | $4.00 | $4.00 | Ordering reference |
| Servo extender PCB fabrication, 1 bare board | 1 | JLCPCB | $4.00 | $4.00 | Ordering reference |
| Parts and boards subtotal | $49.05 | ||||
| Estimated total shipping | 1 | $30.00 | |||
| Total including estimated shipping | $79.05 |
BOM.csv contains the same items and prices. bom.csv includes part numbers and assembly notes. Tax, customs and unlisted wiring costs are not included in the total above.
Design files
| Board | Schematic | PCB | KiCad project | Gerbers and drills |
|---|---|---|---|---|
| Main Pi HAT | Schematic | PCB | Project | ZIP |
| Servo extender | Schematic | PCB | Project | ZIP |
Footprint library · Footprint library table · Journal · Parts and wiring notes · Fabrication notes
USB diagnostic firmware: AI-assisted; not compiled for the ESP32 target or tested on hardware yet.
Project images
Parts
41| Qty | Value | Footprint | References |
|---|---|---|---|
| 4 | MountingHole_2.7mm_M2.5 | MountingHole:MountingHole_2.7mm_M2.5 | MH1, MH2, MH3, MH4 |
| 1 | 100k | Seizo_Reviewed:RC2_R11_R_0805_2012Metric | R11 |
| 1 | 100nF | Seizo_Reviewed:RC2_C5_C_0805_2012Metric | C5 |
| 1 | 10K | Seizo_Reviewed:RC2_R3_R_0805_2012Metric | R3 |
| 1 | 10k | Seizo_Reviewed:RC2_R4_R_0805_2012Metric | R4 |
| 1 | 10k | Seizo_Reviewed:RC2_R12_R_0805_2012Metric | R12 |
| 1 | 10k | Seizo_Reviewed:RC2_R13_R_0805_2012Metric | R13 |
| 1 | 1k | Seizo_Reviewed:RC2_R9_R_0805_2012Metric | R9 |
| 1 | 1uF | Seizo_Reviewed:RC2_C2_C_0805_2012Metric | C2 |
| 1 | 1uF | Seizo_Reviewed:RC2_C7_C_0805_2012Metric | C7 |
| 1 | 1uF | Seizo_Reviewed:RC2_C8_C_0805_2012Metric | C8 |
| 1 | 22 | Seizo_Reviewed:RC2_R8_R_0805_2012Metric | R8 |
| 1 | 22 | Seizo_Reviewed:RC2_R7_R_0805_2012Metric | R7 |
| 1 | 22uF | Seizo_Reviewed:RC2_C4_C_1206_3216Metric | C4 |
| 1 | 4.7k | Seizo_Reviewed:RC2_R15_R_0805_2012Metric | R15 |
| 1 | 4.7k | Seizo_Reviewed:RC2_R14_R_0805_2012Metric | R14 |
| 1 | 470uF | Seizo_Reviewed:RC2_C3_CP_Radial_D8_0mm_P3_50mm | C3 |
| 1 | 5.1k | Seizo_Reviewed:RC2_R6_R_0805_2012Metric | R6 |
| 1 | 5.1k | Seizo_Reviewed:RC2_R5_R_0805_2012Metric | R5 |
| 1 | 75k | Seizo_Reviewed:RC2_R10_R_0805_2012Metric | R10 |
| 1 | AP2112K-3.3 | Seizo_Reviewed:RC2_U3_SOT_23_5 | U3 |
| 1 | Conn_01x06 | Seizo_Reviewed:RC2_J7_PinHeader_1x06_P2_54mm_Vertical | J7 |
| 1 | Conn_01x06 | Seizo_Reviewed:RC2_J6_PinHeader_1x06_P2_54mm_Vertical | J6 |
| 1 | Conn_01x06 | Seizo_Reviewed:RC2_J4_PinHeader_1x06_P2_54mm_Vertical | J4 |
| 1 | Conn_01x06 | Seizo_Reviewed:RC2_J5_PinHeader_1x06_P2_54mm_Vertical | J5 |
| 1 | ESP32-S3-WROOM-1-N8R8 | Seizo_Reviewed:RC2_U2_ESP32_S3_WROOM_1_Thermal030 | U2 |
| 1 | Fuse | Seizo_Reviewed:RC2_F1_Fuseholder_Blade_Mini_Keystone_3568 | F1 |
| 1 | GPIO | Seizo_Reviewed:Pi_HAT_Stacking_Socket_Checked | J1 |
| 1 | Gripper | Seizo_Reviewed:RC2_J2_PinHeader_1x03_P2_54mm_Vertical | J2 |
| 1 | LED | Seizo_Reviewed:RC2_D1_LED_0805_2012Metric | D1 |
| 1 | ONBOARD_OLED | Seizo_Reviewed:RC2_J10_PinSocket_1x04_P2_54mm_Vertical | J10 |
| 1 | PI_FAN | Seizo_Reviewed:RC2_J12_PinHeader_1x03_P2_54mm_Vertical | J12 |
| 1 | REMOTE_SERVO_CABLE | Seizo_Reviewed:RC2_J11_Servo_Terminal_Silk_Clipped | J11 |
| 1 | SW_Push | Seizo_Reviewed:RC2_RESET1_SW_SPST_TL3305A | RESET1 |
| 1 | SW_Push | Seizo_Reviewed:RC2_SW1_SW_SPST_TL3305A | SW1 |
| 1 | Screw_Terminal_01x02 | Seizo_Reviewed:RC2_J9_TerminalBlock_Phoenix_MKDS_1_5_2_5_08_1x02_P5_08mm_Horizontal | J9 |
| 1 | USB_C_Receptacle_USB2.0_16P | Seizo_Reviewed:RC2_J8_USB4105_GND_Heel_Clearance | J8 |
| 1 | Wrist | Seizo_Reviewed:RC2_J3_PinHeader_1x03_P2_54mm_Vertical | J3 |
Questions
How big is the Test1 PCB?
It measures 65 × 56 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Test1 use?
41 parts, built around the ESP32-S3-WROOM-1-N8R8 and AP2112K-3.3. 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 Test1 KiCad files?
From the gmaxdragon/Modular-Pi-Hat repository on GitHub, at the commit this page was made from: the board is hardware/main/test1.kicad_pcb and its schematic hardware/extender/SZSERVOEXTENDER.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Test1 design in my own project?
Its repository states no licence, so its author keeps all rights: ask gmaxdragon before reusing the design.
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