Blog Posts | RBDIMMER

9 Articles

troubleshooting × Feb 2026 ×

DimmerLink Not Detected on I2C: UART Mode Default Issue

Feb 26, 2026

0 504

FAQ

TL;DR: DimmerLink ships from the factory in UART mode . i2cdetect will not show address 0x50 until you send the SWITCH_I2C command ( 02 5B ) over UART at 115200 baud. Also add 4.7 kΩ pull-up resistors...

ac-dimmer dimmerlink I2C troubleshooting

AC Dimmer Flickering at Low Brightness Levels

Feb 26, 2026

0 482

FAQ

TL;DR: Irregular flicker at 5–25% brightness (stable at 50%+) is caused by ZC signal jitter, ISR delays from WiFi on ESP32/ESP8266, or TRIAC holding-current misses. Fix: set a minimum stable level (10...

ac-dimmer ESP32 halogen incandescent troubleshooting tutorial

AC Dimmer Doesn't Turn Off: Residual Glow at 0%

Feb 26, 2026

0 592

FAQ

TL;DR: Setting the dimmer to 0% does not guarantee the lamp turns off. TRIAC holding current keeps the switch conducting at low loads. Fix: call dimmer.setState(OFF) or setMode(OFF_MODE) instead of se...

ac-dimmer halogen incandescent TRIAC troubleshooting tutorial

Zero-Cross Not Detected: AC Dimmer Doesn't Respond to Commands

Feb 26, 2026

0 513

FAQ

TL;DR: An AC dimmer can't regulate the load if the microcontroller isn't receiving the zero-cross signal (the sine wave crossing zero). Without this signal it's impossible to calculate the TRIAC firin...

ac-dimmer Arduino ESP32 troubleshooting zero-cross

Wrong Library: RBDdimmer Instead of rbdimmerESP32 on ESP32

Feb 26, 2026

0 425

FAQ

TL;DR: For ESP32 you need rbdimmerESP32 — not the old RBDdimmer . The old library was written for Arduino AVR: no IRAM_ATTR , no core pinning, no race condition protection. On ESP32 it causes Guru Med...

ac-dimmer Arduino ESP32 troubleshooting

TRIAC Overheating: AC Dimmer Runs Hot or Burns Out

Feb 26, 2026

0 387

FAQ

TL;DR: A TRIAC is an active device with a voltage drop of ~1.2V. At load currents above 2A it dissipates several watts as heat. Without thermal management: overheating, thermal protection triggering, ...

ac-dimmer Arduino TRIAC troubleshooting

ESP32-S2/C3/H2: AC Dimmer Doesn't Work on Single-Core ESP32

Feb 26, 2026

0 546

FAQ

TL;DR: rbdimmerESP32 is designed for dual-core ESP32 (original and S3). ESP32-S2, C3, C6, and H2 are single-core. The library tries to isolate the dimmer task on a dedicated core — which is impossible...

ac-dimmer dimmerlink ESP32 troubleshooting

ESP32 + AC Dimmer: Guru Meditation Error and IRAM_ATTR — Causes and Fix

Feb 26, 2026

0 428

FAQ

TL;DR: If your ESP32 with an AC dimmer crashes ("Guru Meditation Error" or "Cache disabled but cached memory region accessed"), the cause is that the zero-cross ISR handler is not marked with IRAM_ATT...

ac-dimmer ESP32 IRAM_ATTR troubleshooting WiFi

AC TRIAC Dimmer Is Not PWM: How Phase-Cut Dimming Works

Feb 26, 2026

0 482

FAQ

TL;DR: analogWrite() and PWM don't work with an AC TRIAC dimmer. A TRIAC is not a resistor or a DC transistor. It regulates power using phase-cut control : it opens at a precisely calculated moment ea...

ac-dimmer Arduino ESP32 TRIAC troubleshooting

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