2 layers84 × 85 mm
2 layers34.8 × 67.3 mm
CheapMesh
joyel24/CheapMesh25PCB for Heltec HT-CT62: ESP32-C3 + SX1262 lora cheap module. Useful to run MeshTastic. Forked from : https://gitlab.com/paulhausk/CheapMesh
- Size
- 34.8 × 67.3 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 25
- Nets
- 31
- Pads
- 129
- Tracks, vias
- 253, 4
- Pours
- 5
- Routed
- Yes
- KiCad
- KiCad 8.0 (file 20240108)
- Created
- 20 Oct 2024
- Updated
- 18 Mar 2025
Overview
CheapMesh is an open-source printed circuit board by joyel24, from the joyel24/CheapMesh repository on GitHub. It is a 2-layer board of 34.8 × 67.3 mm with 25 parts on 31 nets, routed with 253 tracks and 4 vias.
It is built around the AP2112K-3.3, L78L33ACU and UMH3N. Its parts include 6 resistors, 5 connectors, 4 capacitors, 3 ICs and 1 transistor. It belongs with the radio and wireless boards of this library.
Main components
3
AP2112K-3.3
SOT253.3V 600mA CMOS Low Dropout Linear Regulator with EnableDiodes IncorporatedUncategorised
L78L33ACU
SOT-89-30℃~+125℃@(Tj) 1 1.7V 100mA 3.3V 30V 40uV 49dB@(120Hz) 6mA Fixed Over Current Protection、Over Temperature Protection、Short Circuit Protection Positive SOT-89-3 Voltage Regulators - Linear, Low Drop Out (LDO) Regulators ROHSSTMicroelectronicsVoltage Regulators - Linear, Low Drop Out (LDO) Regulators
UMH3N
SOT-363-55℃~+150℃ 0.5uA 100 100mA 150mW 2 NPN (Pre-Biased) 250MHz 300mV 50V 5V 6.11kΩ NPN SOT-363 Digital Transistors ROHSJiangsu Changjing Electronics Technology (CJ)Digital Transistors
README
README.mdCheapMesh
The goal is to get a cheap Meshtastic node with this chip, therefore some corners where cut.
Several componemts are implemented double, just pick what works best for you.
ToDo
- Add CheapMesh variant to Meshtastic firmware
PCB
Antenna
- Option A: use the onboard antennas
- Option B: use an external antenna with the IPEX connector (and cutting of the onboard lora antenna)
- Option C: use an external antenna with an sma connector (and cutting of the onboard lora antenna)
- Option D: solder on a dipol antenna (and cutting of the onboard lora antenna)
Screen
- Completele optional. Make sure to get a screen with the matching pinout. I recommend SSD1306 128x64 I2C
3.3V Regulator
- Option A: use an external 3.3V powersource
- Option C: use a AP211K-3.3 and the correspondending capacitors
- Option B: use a L78L33 and the correspondending capacitors
- Option D: use a L78L33 pin compatible DC/DC Buck converter like this one
Resetting for flashing
- Option A: populate the UMH3N
- Option B: use an external usb serial interface which can reset the chip
- Option C: Connect GND and HT_EN with a wire. Power on the board (by plugging in) and remove the wire.
Powering the Board
Never connect more than one powersource at a time!!!
- via the usb a pcb connector
- via the usb c connector
- via the Vin Pins
- via the 3.3V Pins
Resistors
All Resitors are 1206 SMD Resistors
R1, R2: Pullup Resistors, 10kOhm
R3, R4: USB Inline Resistors, zero-Ohm
R5, R6: USB-C Resistors, 5,1kOhm
If you want to flash and reflash the HT-CT62 on the pcb, you need to populate R1 and R2. If you not wanna flash the HT-CT62 on the pcb (you have a already programmed chip), you can make a solder bridge on R1.
Building instructions
- Source the the pcb yourself.
- Solder on the components.
- Flash the ESP.
- Option A - use an external usb serial interface like CH34X, CP21XX, FTDI or any other serial interface.
- Option B - use the usb A pcb port
- Option C - use the usb c port (Need to solder it)
BOM
| Reference | Value | Footprint | Qty |
|---|---|---|---|
| AE1,AE2 | Antenna | 2 | |
| C1,C5 | C_Polarized | Depending on power source, +uF if it's instable, optionnal | 2 |
| C3,C6 | C | 0805 or 2012 metric, value depens on your LDO choice | 2 |
| H2,H3 | MountingHole_Pad | 3.2mm M3 DIN965 | 2 |
| J1 | Conn_01x02_Pin | Standard 2.54mm headers | 2 |
| J2 | Conn_01x09_Pin | Standard 2.54mm headers | 9 |
| J4 | USB_C | TYPE-C-31-M-12 | 1 |
| J5 | Conn_Coaxial | SMA 73251-2120 | 1 |
| Q1 | UMH3N | SOT-363 | 1 |
| R1,R2 | 10kΩ | 1206 or 3216 metric | 2 |
| R3,R4 | 0Ω SHUNT | 1206 or 3216 metric | 2 |
| R5,R6 | 5.1kΩ | 1206 or 3216 metric | 2 |
| Screen1 | Conn_01x04_Pin | Standard 2.54mm headers | 4 |
| IO02 | Conn_01x01_Pin | Standard 2.54mm headers | 1 |
| U1 | L78L33 | TO-220-3 | 1 |
| U2 | HT-CT62 | MCU + RF Module: Heltec HT-CT62 | 1 |
| U3 | AP2112K-3.3 | SOT-23-5 | 1 |
License
CheapMesh by PaulHausK is licensed under Creative Commons Attribution-ShareAlike 4.0 International
Parts
25| Qty | Value | Footprint | References |
|---|---|---|---|
| 2 | 10kΩ | Resistor_SMD:R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R1, R2 |
| 2 | 22Ω | Resistor_SMD:R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R3, R4 |
| 2 | 5.1kΩ | Resistor_SMD:R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R5, R6 |
| 2 | C | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C3, C6 |
| 2 | MountingHole_Pad | MountingHole:MountingHole_3.2mm_M3_DIN965_Pad | H2, H3 |
| 1 | |||
| 1 | AP2112K-3.3 | Package_TO_SOT_SMD:SOT-23-5 | U3 |
| 1 | Antenna | RF_Antenna:Texas_SWRA416_868MHz_915MHz | AE2 |
| 1 | Antenna | RF_Antenna:Texas_SWRA117D_2.4GHz_Left | AE1 |
| 1 | C_Polarized | Capacitor_SMD:CP_Elec_8x6.2 | C5 |
| 1 | C_Polarized | Capacitor_THT:CP_Radial_D7.5mm_P2.50mm | C1 |
| 1 | Conn_01x02_Pin | Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical | J1 |
| 1 | Conn_01x04_Pin | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical | Screen1 |
| 1 | Conn_01x09_Pin | Connector_PinHeader_2.54mm:PinHeader_1x09_P2.54mm_Vertical | J2 |
| 1 | Conn_Coaxial | Connector_Coaxial:SMA_Molex_73251-2120_EdgeMount_Horizontal | J5 |
| 1 | HT-CT62 | RF_Module:Heltec_HT-CT62 | U2 |
| 1 | L78L33 | Package_TO_SOT_THT:TO-220-3_Vertical | U1 |
| 1 | UMH3N | Package_TO_SOT_SMD:SOT-363_SC-70-6 | Q1 |
| 1 | USB_A | Library:usb-PCB | J3 |
| 1 | USB_C | Connector_USB:USB_C_Receptacle_HRO_TYPE-C-31-M-12 | J4 |
Questions
How big is the CheapMesh PCB?
It measures 34.8 × 67.3 mm and has 2 copper layers, 1.6 mm thick.
What parts does the CheapMesh use?
25 parts, built around the AP2112K-3.3, L78L33ACU and UMH3N. 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 CheapMesh KiCad files?
From the joyel24/CheapMesh repository on GitHub, at the commit this page was made from: the board is CheapMesh_KiCad/CheapMesh.kicad_pcb and its schematic CheapMesh_KiCad/CheapMesh.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the CheapMesh design in my own project?
Its repository states no licence, so its author keeps all rights: ask joyel24 before reusing the design.
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