Hi! Complete beginner here again — I got the 2-channel module and I’m a bit confused about the wiring.
The module has two sets of connectors. On one side there are these bigger blue screw terminals — I think four of them. On the other side there’s a row of smaller pins with labels that I can barely read (the printing is tiny!).
I can see labels like “L”, “N” on the blue terminals and then “DIM1”, “DIM2”, “ZC”, “VCC”, “GND” on the small pin header side. But there are also two more blue terminals next to the L and N ones that I’m not sure about — are those where my lamps connect?
Basically I need help understanding: which blue terminal is for the power coming IN from the wall and which ones connect to my two lamps going OUT? I really don’t want to wire this wrong since we’re dealing with 230V here.
Is it safe to do this myself if I follow the diagram carefully? Or should I have my electrician neighbor do the AC side?
Thank you in advance!
Good that you’re being careful with mains wiring Wendy. Let me walk through the terminal layout for the 2-channel module.
The module has two separate sides. From a circuit perspective they are completely independent — separated by optocouplers inside the board.
AC side — the four big blue screw terminals (left to right):
- AC-L — this is where your mains Live wire goes in (brown or black wire from the wall)
- AC-N — mains Neutral wire (blue or white wire from the wall)
- CH1-OUT — output for Lamp 1. Connect one wire of your first lamp here
- CH2-OUT — output for Lamp 2. Connect one wire of your second lamp here
The other wire of each lamp connects back to neutral. So the current path for each lamp is: AC-L → module TRIAC → CH-OUT → lamp → back to AC-N.
MCU side — the small pin header (left to right):
- GND — connect to Arduino GND
- DIM1 — control signal for channel 1 → any GPIO pin on your Arduino
- DIM2 — control signal for channel 2 → any GPIO pin
- ZC — zero-cross detection output → must go to an interrupt-capable pin (pin 2 or 3 on Uno)
- VCC — connect to Arduino 5V (or 3.3V if using an ESP32)
Critical safety point: the AC side and MCU side are optically isolated. This means the 230V mains and your 5V Arduino are completely separated inside the module. NEVER bridge the AC neutral to your Arduino GND — they must stay independent. The module handles isolation internally through optocouplers.
Vincent explained it well — thanks!
Just to confirm officially: the terminal layout on the 2-channel module from left to right is:
| Terminal |
Type |
Connect To |
| AC-L |
Input (mains) |
Live wire from mains supply |
| AC-N |
Input (mains) |
Neutral wire from mains supply |
| CH1-OUT |
Output (switched) |
One wire of Lamp 1 |
| CH2-OUT |
Output (switched) |
One wire of Lamp 2 |
The other wire of each lamp connects back to neutral (AC-N). Do NOT wire the load directly between CH1-OUT and CH2-OUT — each channel switches independently against neutral.
On the MCU side: connect VCC to your Arduino’s 5V (or 3.3V for ESP32), GND to Arduino GND, ZC to an interrupt-capable pin, and DIM1/DIM2 to your chosen output pins.
Our hardware connection page has photos and diagrams for every module type — this will make it much easier to follow along visually: Hardware Connection Guide
Regarding doing it yourself — the MCU side (5V, signals) is completely safe to handle. For the AC mains side (230V), if you’ve never worked with mains wiring before, having your electrician neighbor help is a very smart call. Better safe than sorry!
— rbdimmer support team
Thank you both so much — the numbered list and the table make it crystal clear now! And those photos on the hardware connection page are exactly what I needed — I can match the terminals on my actual board to the ones in the picture.
One more question: on the MCU side there’s a GND pin. My Arduino also has a GND pin. I connect those together right? And that’s totally separate from the neutral wire on the AC side?
Just want to make 100% sure because I’ve seen some people online talk about “common ground” and I don’t want to accidentally connect something that links the Arduino ground to the mains neutral. That sounds terrifying.
Quick clarification — yes, you’ve got the right idea!
Module GND ↔ Arduino GND — yes, connect these together. This is the low-voltage logic ground (5V side). It’s perfectly safe.
Module AC-N (neutral) ↔ Arduino GND — NO, never connect these. These are on opposite sides of the optical isolation barrier inside the module.
Think of it as two completely separate electrical worlds:
- AC world (dangerous, 230V): AC-L, AC-N, CH1-OUT, CH2-OUT — all on the blue screw terminals
- MCU world (safe, 5V): VCC, GND, DIM1, DIM2, ZC — all on the pin header
The optocoupler inside the module uses light to transfer the zero-cross signal across the barrier — there is no electrical connection between the two sides. That’s exactly the safety feature that makes this module safe to use with a microcontroller.
So: MCU GND to module GND = correct. Mains neutral to anything on the Arduino = never.
You’re asking exactly the right questions. Let us know how the wiring goes!
— rbdimmer support team
Update: my neighbor came over yesterday and we wired it up together! He did the AC mains side and I did the Arduino side.
Everything is working perfectly — both channels dim independently and the lamps respond smoothly. The photos on the hardware connection page were a lifesaver — I had them up on my phone screen while we were connecting the terminals.
Thank you so much everyone — Vincent for the clear walkthrough, and rbdimmer team for confirming everything and the safety tips. That explanation about optical isolation and the two separate “worlds” made me feel much more comfortable knowing the Arduino side is completely separated from the 230V side.
This community is amazing!