ESP32 Schematic Optimization

This document analyzes the existing setup (Fritzing source + existing hardware documentation) and describes an optimized ESP32 proposal for sensors and relays.

1) Current Analysis (Relevant Signals)

Current firmware pin assignment for ESP32 (src/Config.hpp):

• PIN_DS_SOLAR = GPIO32
• PIN_DS_POOL = GPIO33
• PIN_RELAY_POOL = GPIO25
• PIN_RELAY_SOLAR = GPIO26

Hardware used per documentation:

• 2x DS18B20 Temperature Sensors
• 2-Channel Relay Module (5V)

2) Main Issues in the Previous Setup (Before Optimization)

1. DS18B20 was on GPIO15 (Strapping Pin)

   GPIO15 is a boot-strapping pin on the ESP32. A OneWire bus with pull-up on this pin can negatively affect boot behavior.

2. Relay/Power Supply Coupling

   5V relay modules can cause switching interference (spikes/noise). Without clean separation of logic and load supply, the risk of resets and measurement noise increases.

3. Missing Explicit Fail-Safe Definition in Schematic

   On startup or reset, no pump should turn on unintentionally.

3) Optimized ESP32 Proposal

3.1 Recommended Pin Assignment

Note: For existing installations with old wiring, adjustment of the firmware pins and possibly rewiring is required.

3.1.1 Decision Documentation (Clear Decision)

Decision: For ESP32, the signals are permanently assigned to GPIO32/33 (DS18B20) and GPIO25/26 (Relays).

Why this specific assignment:

1. Boot robustness: Sensors are no longer on strapping pins (in particular no OneWire on GPIO15).
2. Low noise: Sensor GPIOs are logically separated from relay GPIOs, reducing mutual interference during switching operations.
3. Operational safety: Relays on well-usable output pins with clear fail-safe behavior on startup/reset.
4. Maintainability: Consistent, documented standard assignment in firmware and hardware documentation reduces wiring errors and support effort.

Not chosen: The earlier ESP32 assignment (15/16/18/19) because it carries higher boot/noise risk.

3.2 Sensor Optimization (DS18B20)

• Provide a clean 4.7k pull-up to 3.3V for each sensor line.
• Route sensor cables spatially separate from relay/230V lines.
• For longer cables: use twisted pair and a shared clean GND.
• Provide 100nF decoupling near the ESP32 power supply.

3.3 Relay Optimization

• Use a relay module with optocoupler and clearly documented logic level direction (active-low/active-high).
• If the module supports it: separate JD-VCC (relay coil) from VCC (logic) and use star-point grounding.
• Plan appropriate mains protection measures on the pump side (e.g., appropriate fusing/protection circuit for the installation).
• Design relay inputs with additional pull-up/pull-down fail-safe to prevent unintended switching during boot.

3.4 Wiring (Visualization)

                          +---------------------+
                          |        ESP32        |
                          |                     |
DS18B20 Solar DATA  <---->| GPIO32              |
DS18B20 Pool  DATA  <---->| GPIO33              |
Relay IN1 (Pool)    <---->| GPIO25              |
Relay IN2 (Solar)   <---->| GPIO26              |
                          |                     |
3V3 --------------------->| 3V3                 |
GND --------------------->| GND                 |
                          +----------+----------+
                                    |
                                    | common ground
                                    v
                    +----------------+----------------+
                    | 2-Channel Relay Module (5V, opto) |
                    | VCC (Logic)  <- 3V3/5V*         |
                    | JD-VCC (Coil)<- 5V              |
                    | GND           <- GND            |
                    | IN1           <- GPIO25         |
                    | IN2           <- GPIO26         |
                    +----------------+----------------+

DS18B20 Solar: VDD -> 3V3, GND -> GND, DATA -> GPIO32, Pull-up 4.7k to 3V3
DS18B20 Pool : VDD -> 3V3, GND -> GND, DATA -> GPIO33, Pull-up 4.7k to 3V3

* depends on the relay module used (check logic level)

4) Firmware Reference for Rewiring

The recommended pins are implemented in src/Config.hpp. Relevant pins:

• PIN_DS_SOLAR
• PIN_DS_POOL
• PIN_RELAY_POOL
• PIN_RELAY_SOLAR

5) Verification Checklist After Conversion

• Does the ESP32 boot reproducibly (cold/warm) without errors?
• Do relays not switch unintentionally during boot?
• Are temperature measurements stable, even during relay switching?
• No resets during parallel WiFi + relay operation?

6) Operation and Safety

For productive 24/7 operation and safety aspects, please also refer to the project’s security and reliability documentation.

7) See Also

• Detailed assembly guide with step-by-step instructions and manufacturing tips: Hardware Guide
• Complete wiring diagram with RTC module: ESP32 Complete Wiring Schematic