Application Wiring

In the following diagrams there are two sections:

  • Internal
  • External

Internal section reflects a simplified version of the on-board circuit. The External section reflects the wiring that should be used.

Digital Inputs

Bi-directional Opto-coupler Input

Wiring a button

You need an external power supply different from the one used by Raspberry PI, in this way the input circuitry isĀ  isolated from Raspberry PI. You could use the power supply from Raspberry PI but the trade-off is losing the isolation(not recommended).

Digital Outputs

Relay Outputs

The LOAD element in the following diagrams can be a motor, a light bulb, a heating element or something else.

DC source



The DC Source polarity doesn’t matter from the Relay Output point of view, it can matter for your load. The positions of the LOAD and DC Source can be interchanged.

AC source



2 thoughts on “Application Wiring”

  1. Hello,

    Can you please indicate the desired drive strength for these optocouplers (or datasheet) and the resistance of the series shunt?


    1. Hi Devan,
      For DigitalInputs present on DI16ac and DI6acDQ6rly I2C-HATs the minimum drive current is 320uA, the series resistance is 5.6Kohm.

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