This article explains how to safely drive the LY2AC100V AC relay using an M5Stack microcontroller, including coil ratings, contact limits, and inrush current considerations.
Relay Rated Current
The rated current defines the maximum safe current the relay contacts can handle. It depends on:
- Contact material (silver alloy, gold plating, etc.)
- Contact structure (single vs multiple contacts)
- Cooling conditions (ambient temperature and airflow)
These factors determine how much current the relay can safely switch.
Check Required Ratings Before Driving the Relay
1. Coil Ratings
Determine the voltage and current required to energize the relay coil. For LY2AC100V:
| Coil Rating | Value |
|---|---|
| AC100V 50Hz | 11.7mA |
| AC100V 60Hz | 10mA |
| AC110V 50Hz | 12.9mA |
| AC110V 60Hz | 11mA |
| Coil Resistance | 3750Ω |
| Max Allowable Voltage | 110% |
| Power Consumption | 0.9–1.1VA (60Hz) |
A current of 11 mA to 12 mA should be passed through the coil.
When driving the relay through a transistor from M5Stack, ensure the coil receives the correct current.
2. Contact Ratings
These define the safe switching limits for the load connected to the relay output.
| Load Type | Rating |
|---|---|
| AC110V 10A / AC250V 10A | Resistive load |
| AC110V 7.5A | Inductive load (cosφ=0.4) |
| DC24V 10A | Resistive load |
| DC24V 5A | Inductive load (L/R=7ms) |
| Max Contact Voltage | AC250V / DC125V |
| Max Contact Current | 10A (AC/DC) |
Before switching AC100V loads, verify:
- Contact voltage rating ≥ AC100V
- Contact current rating ≥ load current
- Inrush current tolerance (motors, lamps, transformers)
Inrush Current Considerations
Some loads produce a large surge current when switched on. Check the relay datasheet for:
- Rated voltage
- Rated current
- Maximum inrush current (e.g., 20A for LY series)
This ensures the relay can handle startup surges without welding or damage.
Summary
To safely drive the LY2AC100V relay with M5Stack:
- Supply 11–12mA to the coil through a transistor
- Verify contact voltage and current ratings
- Consider inrush current for inductive loads
- Refer to the relay datasheet for exact specifications
This ensures reliable AC100V switching and long relay lifespan.
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