← ESPHome Component | Contents | Next: Arduino IDE Library →

TRIAC AC Dimmer Configuration Guide for Tasmota

This guide explains how to configure and use a TRIAC-based AC dimmer with Tasmota firmware for controlling 230V AC loads such as incandescent lamps, halogen lights, heaters, and other resistive loads.

Overview

A TRIAC (Triode for Alternating Current) dimmer allows you to control the power delivered to AC loads by cutting portions of each AC half-cycle. This is known as phase-cut dimming or leading edge dimming.

How It Works

The dimmer operates by detecting when the AC voltage crosses zero (Zero-Cross Detection) and then delaying the TRIAC trigger pulse. The longer the delay, the less power is delivered to the load:

• 0% dimming: TRIAC fires immediately after zero-cross → full power
• 50% dimming: TRIAC fires at mid-cycle → half power
• 100% dimming: TRIAC never fires → no power

The Tasmota implementation is power-calibrated, meaning 10% dimmer setting results in approximately 10% power consumption. This makes it ideal for applications like directing excess solar energy into a water heater or heat sink.

Typical Applications

• Dimming incandescent and halogen lamps
• Controlling resistive heaters
• Regulating fan speed (universal motors)
• Solar energy diversion to heat sinks
• Any resistive AC load control

Hardware Requirements

Components Needed

1. ESP8266 or ESP32 board with Tasmota firmware installed
2. TRIAC Dimmer Module with Zero-Cross detection output

Popular ready-made modules include:

• RBdimmer AC Dimmer Module (1 or 4 channel)
• Similar modules based on BTA16/BT136 TRIAC with MOC3021 optocoupler

Module Connections

A typical TRIAC dimmer module has the following connections:

Example Schematic

                    ┌─────────────────────┐
                    │   TRIAC Dimmer      │
                    │      Module         │
    ┌───────────────┤                     ├───────────────┐
    │               │  ┌───┐    ┌───┐     │               │
 AC Line ──────────►│  │ZC │    │PWM│     │◄────────── AC Load
 (230V)             │  │Det│    │In │     │            (Lamp)
    │               │  └─┬─┘    └─┬─┘     │               │
 Neutral ──────────►│    │        │       │◄──────────────┘
                    │    │        │       │
                    └────┼────────┼───────┘
                         │        │
                         │        │
                    ┌────┴────────┴───────┐
                    │   ESP8266/ESP32     │
                    │                     │
                    │  GPIO14 ◄───── ZC   │
                    │  GPIO12 ─────► PWM  │
                    │                     │
                    │  VCC ◄───── 3.3V    │
                    │  GND ◄───── GND     │
                    └─────────────────────┘

Tasmota Configuration

Step 1: GPIO Assignment

Configure the GPIO pins in Tasmota's web interface:

1. Navigate to Configuration → Configure Module
2. Set the following GPIO assignments:

Example configuration (using GPIO14 for ZC and GPIO12 for PWM):

After setting the GPIOs, click Save and allow the device to restart.

Step 2: Essential Commands

Before physically connecting the Zero-Cross and PWM signals, enter the following commands in the Tasmota Console:

SetOption99 1

SetOption99 1

Enables detection of the rising edge of the zero-crossing signal. This is required for proper synchronization with the AC waveform.

LedTable 0

LedTable 0

Disables gamma correction. For lamps and heaters, you want a linear power response where 50% dimmer = 50% power. Gamma correction is designed for LED perception and would distort the power curve.

SaveData 0

SaveData 0

Disables periodic saving of dimmer state to flash memory. This prevents flickering that can occur during save operations. Especially recommended for ESP32.

Step 3: Additional Options (Multi-Channel Setup)

If you are using multiple PWM channels (e.g., a 4-channel dimmer module), also execute:

SetOption68 1

This enables independent channel control. Each PWM channel operates as a separate light that can be controlled individually using Channel1, Channel2, etc.

Configuration Summary

Run these commands in sequence before connecting hardware:

SetOption99 1
LedTable 0
SaveData 0

For multi-channel setups, add:

SetOption68 1

Operating the Dimmer

Basic Commands

Channel Control (Multi-Channel)

When SetOption68 1 is enabled:

Fade and Speed Effects

Example sequence for smooth dimming:

Fade 1
Speed 10
Dimmer 75

Calibration Command

ZCDimmerSet

This command is used for calibrating the zero-cross dimmer timing. Refer to Tasmota documentation for specific calibration procedures if you experience timing issues.

Troubleshooting

Light Flickers or Unstable

Possible causes and solutions:

1. SaveData enabled: Run SaveData 0 to disable periodic flash writes
2. Poor Zero-Cross signal: Check wiring, ensure solid connections
3. Incorrect SetOption99: Verify SetOption99 1 is set
4. WiFi interference: Try SetOption65 1 to reduce WiFi sleep transitions

Light Does Not Respond to Dimmer Commands

1. Verify GPIO configuration matches your wiring
2. Check that Counter4 is assigned to the Zero-Cross pin
3. Ensure the TRIAC module is receiving proper AC power
4. Test with Power 1 first to verify basic connectivity

Dimmer Range Too Narrow

Some loads may not dim smoothly across the full 0-100% range. You can adjust the effective dimming range:

DimmerRange 10,100

This sets minimum dimmer at 10% and maximum at 100%. Adjust the minimum value until the load operates reliably at low settings.

Light is Very Dark Even at Higher Dimmer Values

If using LedTable 1 (gamma correction enabled), the response curve is non-linear. For resistive loads:

LedTable 0

ESP32 Specific: Flickering During WiFi Activity

On ESP32, enable the following for more stable operation:

SaveData 0
SetOption65 1

Safety Considerations

Load Compatibility

Quick Reference Card

Initial Setup Commands

SetOption99 1    ; Enable ZC rising edge detection
LedTable 0       ; Linear power response
SaveData 0       ; Prevent flicker from flash writes
SetOption68 1    ; Multi-channel independence (if needed)

Daily Operation

Power ON         ; Turn on
Power OFF        ; Turn off
Dimmer 50        ; Set to 50%
Dimmer +10       ; Increase 10%
Dimmer -10       ; Decrease 10%
Channel1 75      ; Set channel 1 to 75%

Smooth Transitions

Fade 1           ; Enable fading
Speed 10         ; Set transition speed
Dimmer 100       ; Fade to full brightness

References

• Tasmota Lights Documentation
• Tasmota Commands Reference
• SetOption99 Documentation
• AC Dimmer Module on rbdimmer.com

← ESPHome Component | Contents | Next: Arduino IDE Library →