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  • I recently received got my relay expansion board. Id like to try it out, but Im not sure where to start. Ive looked online for example, but haven’t found anything that would explain clearly how to do the electrical connection to the relay. Im seeing 2 IN and 2 OUT on this relay board, I`m not sure were to get the ground. If someone could suggest a tutorial or a webpage with clear instaruction.

  • @claude-hurtubise,

    The relay contacts are just like a simple switch that is open when the relay is off (de-energized) and closed when the relay is on (energized). For example, if you want to light a lamp from a 12V battery, you would connect one terminal of the battery to one of the lamp's contacts. The other lamp contact would go to one of the relay's contacts, and the other relay contact would be connected to the remaining battery terminal.

    The terms "IN" and "OUT" are confusing, as the relay contacts aren't really inputs or outputs; they really are just a pair of contacts that are normally disconnected when the relay is not energized, and are connected when the relay is energized.

  • What do I type into the terminal to get the relays to toggle on and off? They work mint through the web interface but I'd like terminal control.

    (sorry for super basic questions, just saw this thread and figured i'd jump ahead in my learn linux project.)

  • Thanks Jeff, didn't even realize there was expansion tutorials. Much obliged.

  • Thank you Jeff, The confusion part for me was the IN and OUT written on the board. To test the relay I got myself a cheap USB light thing, took it apart and re-wired it and was able to control with the relay, turning it on and off, This was need

  • another question, I would like to use a 5 volt power supply as a source for a light this time and not use 5 volt from the Omega. Would I need to ground my power supply with the omega extension board, the ground on the power supply connected to the ground on the Omega?


  • @claude-hurtubise,

    If you are just using the relay contacts to control power to another device, there is no need to connect the grounds of your supply to the extension board's ground. This is only necessary if you are connecting signal lines (like GPIO pins) to another circuit, since the interconnected circuits usually require a common reference point (usually ground). But since the relay contacts are isolated from other circuitry, it's not necessary to connect the circuit grounds together.

    And although we often talk about voltages in circuits as if they are absolute values, they are actually just values that are relative to the local circuit's ground. If interconnected circuits require inputs or outputs to be within a certain voltage range for proper operation (and they usually do), it's almost always necessary to connect the grounds together.

  • Jeff, thank you for the information, its greatly appropriated


  • administrators

    I've added some wiring information and a little explanation of how to use relays to the Relay Expansion wiki article:

    Please let me know if it's helpful or if I have missed anything.

  • thank you, this is exactly what I was looking for.


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