1-Channel 5V Relay Module
Opto-isolated relay board for safely switching AC appliances or high-current DC loads.
A single-channel relay module with opto-isolation, letting a microcontroller safely switch AC appliances or high-current DC loads.
Specifications
| Control side | 5 V DC, opto-isolated, ~15-20 mA when energized |
| Switching side | Up to 250V AC / 10A or 30V DC / 10A on the common SRD-05VDC-SL-C relay used on most of these boards |
| Trigger logic | Active LOW on most modules — a LOW signal closes the relay, HIGH releases it. Some boards are active HIGH, check the silkscreen or test with a multimeter first |
| Indicator | Onboard LED lights when the relay is energized |
Pinout
| Pin | Name | Description |
|---|---|---|
| 1 | VCC | Power, 5V DC, control side |
| 2 | GND | Ground, control side |
| 3 | IN | Signal input from the MCU — active LOW on most modules |
| 4 | COM | Common, switching side |
| 5 | NO | Normally open — connects to COM when energized |
| 6 | NC | Normally closed — connects to COM when de-energized |
If you're switching mains voltage, treat COM/NO/NC as a separate high-voltage circuit — keep it physically isolated from the 5V control side and never touch it while powered.
Variants
The 1-channel module is the right size when only a single appliance or load needs switching — buying a 4-channel board for one load just wastes space and money. Move up to the 4-channel version as soon as a second or third load needs controlling, and consider a solid-state relay instead of either if the load switches very frequently or the mechanical click/contact wear of a real relay is a concern.
| Variant | Price |
|---|---|
| 1-channel relay module (this listing) | ~$1-2 |
| 4-channel relay module | ~$3-6 |
| Solid-state relay (SSR) | ~$4-10 |