How would you connect this

Hardware
1

I have a 3 wire pigtail that has a 24VDC “hot” wire and two other wires that trigger different modes of the device it belongs to when they are connected to the 24VDC output. I have a Relay Shield and a few of these laying around. So two questions:
A. Do I have the correct relays in either accessory (would love a great reference for sizing relays)?
B. How would the physical wiring be best accomplished? I was thinking I would have to connect the “hot” wire to something like a bus bar then from that back to the individual relays to select which mode or when no connection is active it is off. All relays would be wired in N/O.

2

Your relays should be fine. The main things to consider are the voltage and current you are switching. But with 24VDC and most likely no excessive current draw the Relay Shield and the OMRON relays should be fine (30VDC/10A).

The thing with the OMRON shields is that they are meant for 5V signals with a current draw of 15-20mA. So you’d need some driver (e.g. FET, bipolar transistor, …).
The Relay Shield already works as is.

For the wiring, if you intend to just send the 24VDC coming from the “hot” back into none, one or both of the “mode wires”, you could just feed the hot wire into the common terminal of one relay and have an insulated bridge from that terminal (ensure hot and bridge are securely tightened in the screw terminal) to the common terminal of the other relay and connect the two mode wires to the N/O terminals of each individual relay.
(personal opinion - no liability ;-))

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3

@ScruffR, the relay shield is opto-isolated so they need to be POWERED with 5V but not necessarily controlled with 5V. It would be easy to drive one of the relay control inputs with a Photon GPIO pin as a test. As stated in their description:

Standard interface that can be controlled directly by microcontroller (Arduino , 8051, AVR, PIC, DSP, ARM, ARM, MSP430, TTL logic)

As for the 24VDC "common" then either a bus or as you described is fine as long as everything is well insulated to prevent shorts. :smile:

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4

@peekay123, thanks for the correction there :+1:

I obviously misinterpreted this one to refer to the signal line

But a closer look at the pic actually shows the opto-isolators :blush:

And about the 24VDC: Hence this

Should have stressed this in the original post too. (Edit: done ;-))

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