FAQ
TL;DR: “Less than 100 mA” at 12 V powers a 2-channel ESP-07S lighting node [Elektroda, mmaker, post #18105228]; mind the “max current … 12 mA” per GPIO [Elektroda, khoam, post #18097936] Dual control via wall push-buttons, Wi-Fi and ready firmware (ESPEasy/Tasmota) works.
Why it matters: You can add smart control without rewiring existing 230 V switches or exceeding ESP8266 limits.
Quick Facts
• ESP8266 GPIO current: max 12 mA per pin [Elektroda, khoam, post #18097936]
• Full module draw: < 100 mA at 12 V with Wi-Fi and two relays on [Elektroda, mmaker, post #18105228]
• 230 V opto-input board: ≈ US$2, 3.3 V compatible [Elektroda, khoam, post #18090932]
• Drop-in firmware: ESPEasy, Tasmota, ESPurna—no coding needed [Elektroda, khoam, post #18094288]
• Sonoff Dual alternative: ≈ US$9 delivered, 114 × 52 × 32 mm case [AliExpress listing, 2023]
How can I safely sense a 230 V wall-switch with an ESP-07S?
Use an optoisolator after a resistor-capacitor network or buy a ready 230 V AC detection module; the opto’s LED isolates high voltage while presenting a logic-level signal to the ESP [Elektroda, khoam, post #18090932]
What resistor value suits 230 V detection?
For zero-cross detection, 120 kΩ–180 kΩ in series with the opto LED keeps LED current near 1 mA at 230 Vrms, dissipating < 0.2 W; confirm with the opto data sheet.
Do I need to write C++ code from scratch?
No. Flash ESPEasy, Tasmota or ESPurna and configure GPIOs in the web UI; mmaker’s board worked "without extra tinkering" after flashing ESPEasy [Elektroda, khoam, post #18094288]
What is the safe current per ESP8266 pin?
Limit each GPIO to 12 mA; exceeding this may overheat or latch up the chip [Elektroda, khoam, post #18097936]
How do I toggle a relay with a momentary (bell) switch?
Program the firmware for “toggle” mode: every rising edge on the opto input flips the relay state. ESPEasy calls this the "SwitchToggle" rule.
Linear regulator or buck converter for 3.3 V?
Use a small buck converter; mmaker replaced an LDO after noting wasted heat and now runs cooler at <100 mA draw [Elektroda, mmaker, post #18105228]
Why consider a triac instead of a relay?
Triacs save space and have no mechanical wear but only handle AC loads and need snubbers for inductive lamps [Elektroda, Slawek K., #18099080].
Is a Sonoff Dual easier than custom PCB?
Yes—built-in supply, relays, case and exposed UART. However, its relays are driven by a secondary MCU, so direct GPIO control needs custom mapping [Elektroda, khoam, post #18143837]
Which antenna works inside a ceiling void?
A laptop Wi-Fi antenna or 3 dBi U.FL whip fits; mmaker used a recycled laptop antenna with good coverage through plasterboard [Elektroda, mmaker, post #18105278]
How do I add a heartbeat LED watchdog?
Blink an LED every 500 ms from a timer task. If blinking stops, the ESP has crashed—mmaker calls this his "heartbeat" [Elektroda, mmaker, post #18105228]
What happens if Wi-Fi drops?
Relays continue responding to wall switches because sensing is local. Remote app status simply stops updating until the network returns.
Three-step flashing guide for ESP-07S?
- Solder header to UART pins.
- Hold GPIO0 low, apply 3.3 V, connect USB-TTL.
- Flash firmware with esptool.py, then reboot (GPIO0 high).
Edge case: can excessive opto LED current damage mains wiring?
Yes. If the series resistor is too low, up to 2 W heat can build in the resistor, risking insulation failure. Always verify power dissipation against 230 V.
