XD-621 Induction Touch Switch

🔹 Overview
The XD-621 Induction Touch Switch is a capacitive touch-based switching module designed to control AC loads (mainly lighting) through non-contact touch sensing.
Works through insulating materials like:
Glass
Acrylic
Plastic
Ceramic
Commonly used in mirror lights and concealed switch panels
👉 It is an isolated touch switch, meaning the user is electrically separated from the high-voltage circuit.
🔹 Working Principle
Uses capacitive sensing (induction touch)
Detects change in capacitance when a finger approaches the touch point
Internal circuit processes signal → triggers ON/OFF output
Includes:
Low-noise programmable gain amplifier (PGA)
Internal signal conditioning circuit
👉 Works even through non-conductive surfaces (hidden switch design)
🔹 Electrical Characteristics
Operating Voltage:
AC: 170V – 240V
DC version: 6V – 12V
Max Load Power: ~500W
Max Current: up to 7A
Frequency: 50 / 60 Hz
🔹 Output Characteristics
Type: ON/OFF switching output
Controls:
LED lamps
Fluorescent lamps
Household appliances
Acts as a single-pole switch (SPST behavior)
🔹 Functional Behavior
Touch → toggles state:
First touch → ON
Second touch → OFF
Can sense touch through a defined touch point (≈9–10 mm diameter)
Requires proper alignment of sensing pad for reliable detection
🔹 Physical & Installation Characteristics
Mounting: Behind surface (e.g., mirror backside)
Requires:
Removal of reflective coating at touch point (for mirrors)
Proper alignment of sensor pad
Compact module with separate touch electrode head
🔹 Internal Features
On-chip oscillator (no external components required)
Built-in noise filtering
High interference immunity (reduces false triggering)
Electrical isolation for safety
🔹 Key Technical Features
Capacitive (induction) touch sensing
Works through insulating materials
High-voltage AC load control
Built-in signal amplification and filtering
No mechanical wear (solid-state switching)
Compact and concealed installation
🔹 Advantages
No physical buttons → long lifespan
Safe operation (isolated touch)
Aesthetic (hidden behind surface)
Resistant to dust and moisture (indirectly, due to no openings)
🔹 Limitations
Requires correct installation (alignment critical)
Sensitivity affected by:
Thickness of surface
Material type
Not suitable for very thick or metallic surfaces
Works mainly as simple ON/OFF (no dimming)
🔹 Technical Summary
The XD-621 is a mains-powered capacitive touch switch module that:
Detects touch through insulating materials
Controls high-voltage loads safely
Is optimized for embedded, hidden switch applications (like mirror lighting)