M5Stack Solid State Relay Unit (BT136S)

The M5Stack Solid State Relay Unit lets experienced developers switch compatible single-phase AC loads from a low-voltage M5Stack control signal. It is intended for enclosed prototypes such as heater controllers, lighting automation, and frequent low-noise load switching where a mechanical relay's clicking and contact wear are undesirable. The zero-cross optocoupler and triac provide contactless AC control, but the mains terminals remain hazardous and require qualified installation.

Switch Compatible AC Loads from M5Stack Logic

The low-voltage side accepts the control command while the optocoupler separates it from the AC switching path. Zero-cross operation reduces switching stress for suitable loads, and the solid-state design supports frequent cycling without mechanical contacts.

Heater, Lamp and Appliance Control Prototypes

In a temperature controller, the host can switch a compatible resistive heater according to a temperature band, while separate sensors monitor the process and enclosure. In a lighting prototype, the SSR can provide frequent silent switching. Load type, inrush current, leakage, thermal conditions, and local electrical rules must be evaluated before either application is energized.

Wire the M5Stack BT136S Solid State Relay

Low-Voltage Control Connection

1. Validate the host control logic and fail-off state with the AC side disconnected.
2. Connect the Grove control side only to a compatible 3.3–5V logic interface.
3. Confirm that a restart, communication fault, or watchdog event leaves the command in the intended state.

Qualified Mains-Side Installation

1. Have a qualified person disconnect, lock out, and verify the circuit is de-energized before wiring.
2. Install the unit in an insulated enclosure with suitable clearances, strain relief, earthing, conductor protection, and restricted access.
3. Verify that the load is compatible with triac AC switching and check steady current, inrush current, upstream protection, and thermal rise.
4. Never adjust or service the mains side while energized.

Example Temperature-Control Workflow

1. Read the process temperature and validate the sensor state.
2. Apply a deadband or minimum cycle interval to avoid unnecessary rapid switching.
3. Command the SSR only when the load and all interlocks are valid.
4. Monitor load current and enclosure temperature through separate instrumentation.
5. Remove the command and de-energize the upstream circuit when an overtemperature, overcurrent, sensor, or stuck-on fault occurs.

AC Load Compatibility and Electrical Safety

• The unit is for compatible 220–250V AC loads and is not suitable for DC switching.
• The integrated 2A fuse does not replace correctly coordinated upstream circuit protection.
• Inductive, capacitive, electronic, or high-inrush loads require additional compatibility and derating checks.
• Optical isolation does not make exposed terminals, tracks, or conductors safe to touch.
• This development SSR is not a certified safety relay, disconnect, or protective device.

M5Stack SSR Development Resources

• M5Stack Unit SSR documentation
• UiFlow2 development environment
• Arduino IDE