The SMIH-12VDC-SL-A is a miniature electromagnetic relay designed for DC and AC load switching.
It uses a 12V DC coil to control higher-voltage loads — allowing low-power logic circuits (like microcontrollers) to safely switch high-power devices such as lights, motors, or heaters.
This relay is often used in control panels, home automation, Arduino-based projects, and industrial electronics.
Specification :
| Feature | Description |
|---|---|
| Relay Type | Electromagnetic relay/Power Relay |
| Contact Form | SPDT (Single Pole Double Throw) or changeover contact |
| Number of Pins | 6 pins (2 coil pins + 3 contact pins + 1 NC/NO shared pin) |
| Coil Voltage | 12 V DC |
| Contact Rating | 10 A at 250 V AC or 10 A at 30 V DC |
| Coil Power Consumption | ~0.36 W |
| Mounting Type | PCB mounting |
| Contact Resistance | ≤ 100 mΩ (initial) |
| Insulation Resistance | ≥ 100 MΩ (at 500 VDC) |
| Operate Time | ≤ 10 ms |
| Release Time | ≤ 5 ms |
| Dielectric Strength | 1500 VAC between coil and contacts |
| Ambient Temperature Range | -40°C to +85°C |
| Mechanical Life | >10 million operations |
| Electrical Life | >100,000 operations at rated load |
Pin Configuration (6 Pins)
| Pin No. | Function | Description |
|---|---|---|
| 1 | Coil (+) | Connect to +12V DC |
| 2 | Coil (–) | Connect to ground or transistor output |
| 3 | Common (COM) | Connected to moving contact |
| 4 | Normally Open (NO) | Connected to COM when relay is energized |
| 5 | Normally Closed (NC) | Connected to COM when relay is not energized |
| 6 | Optional Contact / Support pin | For mechanical stability (depends on version) |
Note:
In the PCB layout, the coil pins are often on one side, and the switching contacts are on the opposite side.
Typical Electrical Characteristics
| Parameter | Value |
|---|---|
| Coil Resistance | ≈ 400 Ω |
| Pull-in Voltage | ≤ 9 VDC |
| Drop-out Voltage | ≥ 1.2 VDC |
| Max Allowable Coil Voltage | 15.6 VDC |
| Contact Material | Silver Alloy |
| Contact Resistance | ≤ 100 mΩ |
| Dielectric Strength | 1500 VAC (coil to contact) |
Tips for Proper Use
-
Use flyback diode:
Always place a 1N4007 diode (or similar) across the relay coil to protect your microcontroller from voltage spikes when turning off the relay. -
Use transistor or MOSFET driver:
The relay coil draws ~30 mA — too high for direct GPIO control from Arduino or ESP32. Use a 2N2222, BC547, or 2N3904 transistor to switch the relay. -
Use separate power supply if controlling multiple relays (avoid microcontroller brownout).
-
Avoid rapid switching — relays are mechanical; constant on/off cycles cause wear.
-
Observe contact ratings — do not exceed 10 A or 250 VAC / 30 VDC loads.
-
Add snubber circuits (RC or MOV) when switching inductive loads like motors or solenoids.
Common Applications
-
Home automation (light/fan control)
-
Smart power control with Arduino / ESP8266 / ESP32
-
Automotive DC load switching (lights, pumps)
-
Industrial control and PLC systems
-
Motor and solenoid activation
-
Security or alarm systems
Quick Summary Table
| Parameter | Value |
|---|---|
| Model | SMIH-12VDC-SL-A |
| Coil Voltage | 12 V DC |
| Coil Current | 30 mA (approx.) |
| Contact Rating | 10 A @ 250 VAC / 30 VDC |
| Contact Type | SPDT (1 C/O) |
| No. of Pins | 6 |
| Mounting | PCB |
| Operate Time | ≤10 ms |
| Release Time | ≤5 ms |
| Insulation Resistance | ≥100 MΩ |
| Dimensions | ~19 × 15.5 × 15 mm |
