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8 Channel Opto Isolated Relay Module

8 Relay Board This Wiki page contains additional information for the MOD-RELAY8-5V-10A-T2 from Modtronix.

For safety reasons we DO NOT recommend using this module with voltages above 12V. Any use of this module is at your own risk! Always take necessary safety precautions when working with high voltages to prevent electrical shock! We will take no responsibility for any damage, personal injury or death incurred due to using this unit with high voltages!

This modules contains 8 relays, rated at 5V and 10A. Each relay has a LED indicator. It can be used to control various appliances, and other equipment with large current. It can be controlled directly with 3.3V or 5V logic signals from a microcontroller (Arduino, 8051, AVR, PIC, DSP, ARM, ARM, MSP430, TTL logic).

Each relay has an Optocoupler, providing optical isolation. Each relay also have a freewheeling diode protection.

This module has a 6 pin header(standard 2.54mm pitch) for connecting power (5V and GND), and controlling the 8 relays. These pins have the following functions:

  • IN1 to IN8: Controls relays 1 to 8, active Low! Relay will turn on when this input goes below about 2.0V
  • GND: Connect 0V to this pin. Is used to power the board (optocouplers and relays).
  • VCC: Connect 5V to this pin. Is used to power the board (optocouplers and relays).
Side View
Bottom View
Top View


  • Channels: 8 Relays
  • Relay Voltage: 5V
  • Relay Coil Current: 72mA at 5V per relay
  • Relay Output Current: 10A at 250VAC, 10A at 30VDC
  • Board Supply: 5V supply voltage
  • Input Type: Opto Isolated inputs
  • Power LED: 1 LED for power indication
  • Channel LEDs: 8 LEDs to indicate state of each relay
  • Module dimension: 134mm x 52mm


Wiring is very easy, and is shown in the diagram below.

If opto isolation is required, the 5V power supply should be separate from the controller(Arduino, STM32..) power supply, as shown in the picture below. This is the recommended way to use this module!

If no opto isolation is required, the power for the relay module (VCC and GND pins) can be taken from the controller if available. Just ensure the controller can supply enough power for the relay module. Each relay requires about 72mA, so all 8 relays will require about 580mA! Additionally they might introduce noise to the controller power supply, which could cause glitches.

Wiring Diagram
products/modules/relay/mod-relay8-5v-10a-t2.txt · Last modified: 2017/02/17 01:23 by modtronix