ESP32 PCB Design Assistance
I need a PCB where the center is an ESP32. There's 2 motors connected via CAN (3.3v, tx, rx, ground, on 2.54mm spacing female), an external servo driver board, which needs ground, tx, rx (all female header pins). The battery connects to a 14.8 power bus on the PCB. From this 14.8 power bus, we connect to a small buck converter (3.3V, power and ground from PCB 14.8V) (external, not on PCB), which in then powers the ESP 32. The 14.8 power bus also powers another external, not on the pcb, buck converter which returns back 12.2 V to a new power bus, which just needs to receive up to 20amps via female. From this power bus, we power the servo driver as well ( via 2 male headers, gnd and 12.2v, on the PCB)
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Power Budget
Architecture
- Battery input: 14.8 V nominal on
14V8bus via J4. - External buck converter #1: takes
14V8from J5 and returns3V3on J5 for ESP32 and logic headers. - External buck converter #2: takes
14V8from J6 and returns12V2on J6 for high-current 12.2 V bus J7 and servo power header J8.
3.3 V rail loads
Table
| Load | Typical | Peak / design allowance | Notes |
|---|---|---|---|
| ESP32-WROOM-32E | ~240 mA | 500 mA | WiFi TX peaks; external buck should be rated at least 1 A for margin. |
| Motor logic headers J1/J2 3.3 V pins | unknown | user-defined | If external motor boards draw logic power from this PCB, include them in the 3.3 V buck rating. |
Recommended 3.3 V buck output rating: >=1 A, more if motor interface electronics are powered from J1/J2.
12.2 V rail loads
Table
| Load | Typical | Peak / design allowance | Notes |
|---|---|---|---|
| 12.2 V bus J7 | unknown | up to 20 A | User requirement. |
| Servo driver power J8 | limited by header | up to 3 A connector rating | Do not exceed the installed 2.54 mm male header rating. |
Recommended 12.2 V buck output rating: 20 A minimum if the full J7 bus current is required. At 12.2 V and 20 A, output power is 244 W.
Reflected 14.8 V current
Assuming 90% buck efficiency for the 12.2 V converter:
I_14V8 = (12.2 V * 20 A) / (14.8 V * 0.90) = 18.3 AThe 14.8 V bus should therefore be designed for at least 20–25 A if the 12.2 V rail may deliver 20 A. The 3.3 V ESP32 buck adds only about 0.25 A at 14.8 V for a 1 A / 3.3 V output at 90% efficiency.
Design decisions / warnings
- I used terminal-block style connectors for high-current buses because 2.54 mm headers are not safe for 20 A.
- The motor links are wired as 3.3 V logic TX/RX because the requested pinout was
3.3V, TX, RX, GND. True CAN requires CANH/CANL and a CAN transceiver, not direct TX/RX wiring. - J8 is a 2.54 mm male header rated around 3 A; it should only feed low-current servo-driver control/power input, not the full 20 A bus.
Architecture
3.3 V rail loads
12.2 V rail loads
Reflected 14.8 V current
Design decisions / warnings
