1-Channel 5V Solid-State Relay (SSR) Module - Low-Level Trigger, 250V 2A AC

Specifications

• Module Type: Solid State Relay (SSR)

• Control Voltage (Input): 5V DC

• Trigger Logic: Low-Level Trigger (0V-1.5V = ON, 2.5V-5V = OFF)

• Input Quiescent Current: 0mA

• Input Operating Current: ~12.5mA

• Load Voltage (Output): 100V to 240V AC (NO DC LOADS)

• Max Load Current: 2A (Fused)

• Switching Type: Zero-Crossing

• Isolation: Optical (Phototriac)

• Dimensions: ~25mm (W) x 35mm (L) x 25mm (H)

Key Applications and Projects

• Silent Smart Home Automation: Controlling bedroom lamps or desk fans via a Raspberry Pi, where the clicking of mechanical relays would be annoying.

• Aquarium Controllers: Switching AC heaters and AC water pumps on and off repeatedly based on temperature sensor readings without wearing out mechanical contacts.

• Holiday Lighting Displays: Creating rapid, synchronised light shows with AC Christmas lights, taking advantage of the high-speed switching capabilities of the SSR.

Unlock New Capabilities (Project Evolution) The Automated Fermentation Chamber: Building a climate-controlled enclosure for brewing kombucha, beer, or proofing dough? Precise temperature control requires constantly cycling a heater on and off. A mechanical relay will burn out over a few months of rapid cycling. Evolve your build! Use this SSR to control a small AC heating pad, driven by an Arduino reading a DS18B20 temperature sensor. The solid-state nature ensures millions of silent, reliable cycles, maintaining your chamber at the exact degree required for perfect fermentation!

Package Includes:

• 1 x 1-Channel 5V Low-Level SSR Module with 2A Fuse

FREQUENTLY ASKED QUESTIONS (FAQ)

1. What is a Solid-State Relay (SSR)? An SSR is an electronic switching device that switches on or off when a small external voltage is applied across its control terminals. Unlike mechanical relays, it contains no moving parts, using semiconductor properties (like a Triac) to switch the load.

2. Can I use this to turn on a 12V DC motor or LED strip? No. This is the most important limitation of this module. The Omron G3MB-202P chip uses a Triac, which can only turn off when the voltage crosses zero. DC voltage never crosses zero. If you use it on a DC load, it will turn on but will never turn off until you disconnect the battery.

3. What does "Low-Level Trigger" mean? It means the relay turns ON when the signal pin (CH1) is pulled to Ground (0 Volts). If you send 5V (HIGH) to the CH1 pin, the relay turns OFF.

4. What is the green component shaped like a resistor on the board? That is a specialized 2A resistive fuse. It is a safety feature designed to blow and break the circuit if your AC appliance pulls more than 2 Amps, protecting the relay chip and your house wiring.

5. How much power can 2 Amps handle? Watts = Volts x Amps. If you are on a 120V AC grid (like in the US), 2A allows you to control up to 240 Watts. If you are on a 240V AC grid (like the UK or India), 2A allows up to 480 Watts.

6. Can this handle a large AC window air conditioner or a space heater? No! Those appliances pull significantly more than 2 Amps (often 10A to 15A). Attempting to run them through this module will instantly blow the green fuse.

7. Does this relay make a clicking noise? No, it is 100% silent because there are no physical metal contacts hitting each other.

8. How do I wire the input (DC) side? Connect your 5V power supply to the DC+ terminal, your ground to the DC- terminal, and your microcontroller's digital output pin to the CH1 terminal.

9. How do I wire the output (AC) side? You wire it in series with the Live (Hot) AC wire. Cut the Live wire of your appliance. Insert one end into one screw terminal of the blue AC block, and the other end into the second screw terminal. (Leave the Neutral and Ground wires unbroken).

10. What is "Zero-Crossing" switching? The Omron chip features a zero-cross detector. When you trigger the relay, it waits a fraction of a millisecond until the AC sine wave hits 0 Volts before turning on. This eliminates electrical noise and sudden current spikes, which is great for the lifespan of your appliances.

11. Can I use PWM to dim an AC light bulb with this module? No. Because it uses zero-crossing switching, it cannot perform "phase-angle cutting" required for standard AC dimming. It is strictly an ON/OFF switch.

12. Will this module work with a 3.3V microcontroller like an ESP32 or Raspberry Pi? The module requires 5V to power the DC+ line. However, because it is a Low-Level trigger, pulling the CH1 pin LOW with a 3.3V logic device will successfully trigger the relay, provided your 3.3V board and the 5V power supply share a common ground.

13. Does this module heat up during operation? At low loads (under 1A), it generates virtually no heat. If pushed to its maximum 2A limit continuously, the black Omron chip will become warm to the touch, which is normal for semiconductors.

14. What do the LEDs on the board indicate? Typically, there is a power LED that illuminates when 5V is applied to DC+ and DC-, and a secondary trigger LED that illuminates when the CH1 pin is pulled LOW, confirming the relay is activated.

15. Is my microcontroller electrically isolated from the AC voltage? Yes. The Omron relay chip uses internal optical isolation (a phototriac). There is no physical electrical path between your 5V logic side and the deadly AC side.

16. Why is my LED light bulb flickering or staying dimly lit when the relay is OFF? Solid-state relays inherently possess a tiny amount of "leakage current" even when turned off. For standard appliances, this is imperceptible. However, modern ultra-low-wattage LED bulbs might harvest this leakage current and flicker or glow dimly.

17. What happens if the green fuse blows? If the fuse blows, the relay will stop sending power to the load permanently. To fix it, you would have to desolder the blown green fuse and solder in a replacement, which is why you should never exceed 2 Amps.

18. Is it safe to touch the bottom of the board while it's plugged into the wall? Absolutely NOT. The bottom of the PCB contains exposed solder joints carrying live 120V/240V AC mains voltage. It must be mounted inside an insulated plastic enclosure before plugging it in.

19. What is the minimum load requirement? Triacs usually require a very small minimum current (often a few milliamps) to successfully "latch" and stay on. If your load is microscopic, the relay may behave erratically.

20. Can I trigger the relay rapidly (e.g., 10 times a second)? Yes, solid-state relays excel at rapid switching without degradation. However, remember that because it switches at the AC zero-cross, your maximum practical switching frequency is tied to your AC grid frequency (50Hz or 60Hz).