Multiple Shields

I'm not too familiar yet with Arduino. I don't think the software will be difficult for me, but the application I have in mind will require the use of at least 2 shields (relay cards) plus some dedicated signal condition circuitry. Do the shields just stack on top of each other? They could all get power and access to I/O pins, but what about other connections to these shields?

In short yes but is dependent on the shields you choose

w7qdm: Do the shields just stack on top of each other?

That is what the Arduino hardware system is all about. You just need to note:

  1. pin clashes, which are rare and usually easily fixed in software

  2. some boards are power hungry and need a separate supply

  3. you may require a board with long legs in order to fit over some bulky item.

"1. pin clashes, which are rare and usually easily fixed in software "

You may have to Not stack them so control signals can be separately driven.

w7qdm: ...the application I have in mind will require the use of at least 2 shields (relay cards)

A separate 8-relay card could be much easier/cheaper than a stack of modded shields.

What are you planning to switch with the relays. Leo..

w7qdm: I'm not too familiar yet with Arduino. I don't think the software will be difficult for me, but the application I have in mind will require the use of at least 2 shields (relay cards) plus some dedicated signal condition circuitry. Do the shields just stack on top of each other? They could all get power and access to I/O pins, but what about other connections to these shields?

Dependent on your package size a pair of relay boards may suit you but as suggested a bank of 8 or 2 banks of 4 relays may provide a better path, I am currently working with a 4 relay shield for the uno the one I have is working but much cheaper in quality than the standalone units on their own control boards

https://seeeddoc.github.io/Relay_Shield_V2.0/

There is a 35volt relay contact limit for that shield. That's why I asked what OP is switching.

8-channel relay boards can be configurated for opto isolation, with a separate 5volt relay supply. That could make them safer for mains applications (if done right). Leo..

Wawa: There is a 35volt relay contact limit for that shield. That's why I asked what OP is switching.

8-channel relay boards can be configurated for opto isolation, with a separate 5volt relay supply. That could make them safer for mains applications (if done right). Leo..

Yeah I'm not sure I would trust or recommend the OP to use high voltage i.e. 110v-220v regardless if it stated it could, the shield I listed is of low quality but I'm working with nothing over 12v so it suits my use case and may suit his as well

To Wawa: (I hope I'm using forum correctly)

Where can I find information on the 8 relay card you mention? In answer to your question, "what am I controlling with the relays?", I am driving bigger relays to control AC power in the 240 VAC, 30 amp range.

Did you Google something like "Arduino 8-relay board", and look at images. Almost every corner store sells them.

What is the coil voltage of those "bigger relays". 12volt, 24volt, mains voltage? Leo..

Wawa: You're right! Many 8-relay cards are available. (Sorry, I'm pretty new to this venue) The power relays I need to control will probably have 24 VDC coils.

w7qdm:
The power relays I need to control will probably have 24 VDC coils.

If you can share power relay supply ground with Arduino ground, then a relay board might not be needed.
A TPIC6B595 shift register can switch eight 24volt relays if coil current is <100mA.
Post a link to the relays.
Leo…

TPIC6B595 is good for 150mA. TPIC6C595 is good for 100mA.

TPIC6595 is good for 250mA. TPIC6A595 and TPIC6A596 are good for 350mA.