Relay Boards
Relay Boards
A Relay Board allows a low-voltage controller, such as an ESP8266, ESP32, Arduino, or Raspberry Pi, to safely switch higher-voltage or higher-current electrical loads.
Relay boards are commonly used in Christmas lighting displays to control traditional AC decorations, flood lights, motors, inflatables, and other devices that cannot be driven directly by a controller's output pins.
What is a Relay?
A relay is an electrically operated switch.
A low-voltage control signal energizes the relay, causing internal contacts to open or close an independent electrical circuit.
This allows a small controller to safely control devices operating at much higher voltages or currents.
Types of Relay Boards
Several types of relay boards are available.
Mechanical Relay Boards
Mechanical relays use physical contacts to switch power.
Advantages include:
- Can switch AC or DC loads
- Handles relatively high current
- Electrical isolation between control and load
- Inexpensive and widely available
Disadvantages include:
- Audible clicking
- Contact wear over time
- Slower switching speed
- Not suitable for dimming
Solid State Relay (SSR) Boards
Solid State Relays use semiconductor devices instead of moving contacts.
Advantages include:
- Silent operation
- Fast switching
- Long operating life
- No mechanical wear
Some SSRs are capable of dimming AC loads when designed for phase-angle control.
See Solid State Relay for additional information.
Typical Christmas Lighting Uses
Relay boards are commonly used to control:
- Traditional incandescent light strings
- Flood lights
- Spot lights
- Rope lights
- Inflatables
- Small motors
- Fog machines
- Snow machines
- Other switched electrical loads
They are generally not used to control smart pixels, which require continuous data communication rather than simple on/off switching.
Relay Boards vs. SSRs
| Mechanical Relay | Solid State Relay |
|---|---|
| Physical contacts | Semiconductor switching |
| Audible click | Silent |
| Limited switching life | Very long life |
| Cannot dim | Some models support dimming |
| Excellent for simple switching | Excellent for frequent switching |
Safety
Relay boards switch potentially dangerous voltages.
Always:
- Follow local electrical codes.
- Use properly rated relays.
- Install appropriate fuses or circuit breakers.
- Keep high-voltage wiring isolated from low-voltage electronics.
- Enclose exposed wiring in suitable electrical enclosures.
Never exceed the relay manufacturer's voltage or current ratings.