A modular ESP‑12E (ESP8266) hardware design for pressure sensing, load driving, and safe power management with battery charging and automatic source switchover.

This repository contains KiCad 9.0.2 schematics for a pressure‑control system built around an ESP‑12E module, dual precision pressure measurement channels, high‑side battery/adapter power path control, and isolated MOSFET drivers for solenoids and a motor. The design includes an onboard CN3703 Li‑ion charger, AMS1117‑3.3/LM7805 regulators, TLP250 gate drivers, and IRF540N power MOSFETs with Schottky flyback protection, organized across four hierarchical sheets.

• ESP‑12 top‑level: ESP‑12E module, boot/EN/RST conditioning, ESD protection, sensor ADCs, and header breakout.
• MOSFETs: Four opto‑isolated TLP250 driver channels feeding IRF540N MOSFETs for Sol_1…Sol_4 and Motor outputs with MBR745 freewheel diodes and LED indicators.
• Automatic Load Switchover: LTC2952 power management, dual 2SJ174 P‑MOSFET path control, and local 3.3 V/5 V regulation for state control and status.
• Battery Charger: CN3703 Li‑ion charger with SS36 rectifiers, 22 µH power inductors, 0.1 Ω sense, and charge/done LED indicators.

• ESP12E.kicad_sch: Top‑level ESP‑12 sheet with sensors, regulators, ESD, UART, and I/O header.
• MOSFETs.kicad_sch: Isolated drivers, MOSFET power stages, connectors for solenoids and motor.
• Automatic Load Switchover.kicad_sch: LTC2952 control, P‑channel power multiplexing, timing/configuration network.
• Battery Charger.kicad_sch: CN3703 charger stage with power path elements and indicators.

• Input power is provided via a 12 V PWR connector with bulk filtering (e.g., 470 µF/16 V C3) feeding a 5 V LM7805 and a 3.3 V AMS1117 rail, duplicated where needed on control sheets.
• Automatic source switchover uses LTC2952 to supervise ON/OFF timing, power‑fail, watchdog, and gate‑drive outputs for back‑to‑back 2SJ174 P‑MOSFETs controlling PWR_in/PWR_out and Battery_in.
• The CN3703 charger implements Li‑ion charging with SS36 diodes, 22 µH inductors, 0.1 Ω current sense, and CHRG/DONE LED status, feeding the battery power domain.

• Two HX710(A/B) precision ADC channels interface differential pressure sensors labeled MPS‑2108, each with Vo+/Vo−, VCC, and local decoupling.
• Each ADC section provides AVDD/DVDD partitioning, PD_SCK/DOUT digital lines to the ESP‑12E, and VREF/AGND nodes for stable measurement.

• ESP‑12E (ESP8266) module exposes GPIO0–GPIO16, UART TX/RX, SPI, ADC (A0), EN, and RST, with pull networks for proper boot mode and reset behavior.
• ESD protection diodes (CESD5V0D3) are placed on sensitive I/O and rails including UART, reset, and 3.3 V nodes to improve robustness.

• Four TLP250 opto‑gate drivers provide isolation between the ESP‑12 logic domain and the IRF540N power stages, each with dedicated gate resistors and LED activity indicators.
• Outputs are presented on headers as Sol_1, Sol_2, Sol_3, Sol_4, and Motor, each clamped by MBR745 Schottky diodes for inductive flyback protection.

• J4 12v PWR: main DC input for the regulator stages and system rails.
• J6–J10: load connectors labeled Sol_1…Sol_4 and Motor for external actuators.
• J3 UART: UART header with GND and supply pins for programming and debug.
• J1/J2 headers: general I/O and power breakouts, including +3.3 V, +5 V, and ground.

• EN and RST are broken out with push‑buttons and pull resistors for stable power‑up and manual reset.
• Boot straps on GPIO0/GPIO2/GPIO15 are provisioned via resistor networks to ensure normal boot, with access for entering programming mode via GPIO0.

• Transient suppression uses CESD5V0D3 devices on supply and data lines close to connectors and the ESP‑12E pins.
• Multiple LEDs indicate power presence, driver activity, and charger state (CHRG/DONE), aiding bring‑up and troubleshooting.

• Designed with KiCad E.D.A. 9.0.2; open the top‑level ESP12E.kicad_sch and traverse hierarchical sheets for editing and ERC.
• Validate regulator thermal performance and inductor/diode current ratings for intended solenoid and motor loads before committing to PCB or enclosure.

• MCU and IO: ESP‑12E module with 1×16 IO header and a 1×6 programming/UART header.
• Sensing: 2× HX710(A/B) ADCs with MPS‑2108 pressure sensors and precision analog routing.
• Power: LM7805_TO220, AMS1117‑3.3, bulk/tantalum/ceramic decoupling, and LTC2952‑controlled high‑side switching with 2SJ174 P‑MOSFETs.
• Charger: CN3703 with SS36, 22 µH inductors, 0.1 Ω sense, and charge/done LEDs.
• Drivers: TLP250 opto drivers and IRF540N MOSFETs with MBR745 clamps and LED indicators.

• Power the board from the 12 V input or the battery domain once assembled and verified on bench with dummy loads.
• Program the ESP‑12E via the UART header using normal ESP8266 flashing procedure after pulling GPIO0 low for programming mode.

• Observe proper isolation, heat sinking, and wiring gauge for motor/solenoid currents, and verify flyback diodes are oriented correctly before first power‑up.
• Double‑check charger and battery polarity, and do not operate unattended during initial charge‑cycle validation.

Metanoia — designed by Mohamed Yousry, Mechatronics/Embedded Hardware Engineer.

This project is licensed under the MIT License.

Schematic Rev v1.0, dated 2025‑09‑07.

• Complete multi‑sheet KiCad schematics with hierarchical organization for core MCU, drivers, switchover, and charging.
• Net labels and headers to speed firmware pin mapping for UART, SPI, I2C, and ADC integration on the ESP‑12E.

The project combines reliable power‑path control, isolated high‑current drivers, and precision sensing into a compact ESP8266 platform for pressure‑based automation tasks.