RelayBoard
About the RelayBoard PCB
RelayBoard is an open source PCB design by slimmsehli, published on GitHub. It is a 2-layer board measuring 74.5 × 63 mm, with 33 components from 9 distinct parts.
Other key parts include the PC817. By type, the board carries 8 diodes, 8 resistors, 5 connectors, 4 ICs, 4 transistors and 4 relays.
From the project
Relay Board for 250VAC/10VDC controlled by 5v
🟢 4-Channel Relay Board with Opto-Isolation for Arduino/Raspberry Pi
This project is a modular, 4-channel relay control board designed for microcontrollers like **Arduino, Raspberry Pi, ESP32, etc. The board features opto-isolation for electrical protection and safety, and is ideal for home automation, IoT, or industrial control applications.
- ✅ 4 independent relays (SPDT type) – control AC/DC loads up to 250V AC / 30V DC - ✅ 4 opto-isolated inputs – control each relay with 3.3V or 5V logic - ✅ Load-side isolation – added safety through PCB cutouts (drilled part under relay contacts) - ✅…
Main components on the RelayBoard
RelayBoard bill of materials (BOM)
33 components, 9 distinct parts.
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 4 | PC817 | DIP-4_W7.62mm | U1, U2, U3, U4 |
| 4 | BC817 | SOT-23 | Q1, Q2, Q3, Q4 |
| 4 | Conn_01x03_Pin | TerminalBlock_bornier-3_P5.08mm | J1, J2, J3, J4 |
| 1 | Conn_01x06_Pin | PinHeader_1x06_P2.54mm_Vertical | J5 |
| 4 | SANYOU_SRD_Form_C | Relay_SPDT_SANYOU_SRD_Series_Form_C | K1, K2, K3, K4 |
| 4 | 1N4007 | D_DO-41_SOD81_P10.16mm_Horizontal | D1, D4, D6, D8 |
| 4 | LED | LED_1206_3216Metric_Pad1.42x1.75mm_HandSolder | D2, D3, D5, D7 |
| 4 | 1K | R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | R1, R3, R5, R7 |
| 4 | 510R | R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | R2, R4, R6, R8 |
RelayBoard design files
The KiCad project lives in the slimmsehli/RelayBoard repository on GitHub; these links point at the commit this page was built from.
RelayBoard: common questions
How big is the RelayBoard PCB?
The RelayBoard measures 74.5 × 63 mm, has 2 copper layers and is 1.6 mm thick.
How many components are on the RelayBoard?
33 components, from 9 distinct parts. The full bill of materials is listed on this page.
Where can I download the RelayBoard design files?
From the slimmsehli/RelayBoard repository on GitHub, which has the KiCad layout and the schematic; the links under Design files point to each one.
Can I use the RelayBoard design in my own project?
The repository has no license, so all rights stay with slimmsehli. Use it as a reference, and ask the author before reusing the design.
Earlier revisions in the repo: Relay_board_v0, Relay_board