ESP32 CAN Bus Relay Board: 8 Isolated Outputs for Automotive Projects
8 isolated digital inputs. 8 relay outputs. CAN bus. Ethernet. Does this ESP32 relay board belong in your automotive build?
The Waveshare ESP32-S3-ETH-8DI-8RO-C handles high-voltage switching, bus communication, and DIN rail mounting in one unit. We test it as a CAN bus I/O node for vehicle body control — driving relays from CAN frames, reading isolated digital inputs, and pushing telemetry over Ethernet to our edge gateway.
WHAT WE COVER
Relay switching under load: 8 channels at 250VAC/30VDC, 10A rated
Isolated digital inputs with optocoupler protection — noise immunity testing
CAN bus integration: sending/receiving frames at 500 kbps with the onboard transceiver
Ethernet (W5500) throughput: pushing I/O state changes to an MQTT broker
DIN rail mounting and 24V industrial power input — does it survive vehicle voltage swings?
Real gotcha: the relay driver ICs are not socketed — here's what that means for field repair
HARDWARE
Waveshare ESP32-S3-ETH-8DI-8RO-C
ESP32-S3 @ 240 MHz, 16MB Flash, 8MB PSRAM
8× relay outputs (NO/COM/NC), 8× isolated digital inputs (5-36V)
CAN bus (onboard transceiver), RS485, Ethernet (W5500)
DIN rail enclosure, 7-36V DC input
SKU: ESP32-S3-ETH-8DI-8RO-C
USE CASES
Vehicle body control module (lights, locks, fans)
Industrial I/O node with CAN bus networking
Off-grid automation: pump control, sensor monitoring
CAN-to-Ethernet bridge for telemetry aggregation
OPEN SOURCE
Test firmware, CAN frame definitions, and wiring diagrams at github.com/trailcurrent/esp32-can-io
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CHAPTERS
00:00 — What this board replaces
01:15 — Hardware walkthrough: relays, inputs, CAN
02:45 — CAN bus I/O node firmware
04:30 — Switching relays under load
06:00 — Ethernet telemetry to MQTT
07:30 — DIN rail mounting and power testing
08:30 — Production readiness assessment
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