Multiway Switch DPDT arduino. Software? Same data pin? External DPDT relay?

Other Hardware General Electronics
1

Hello,

I'm thinking about automating some light switches around the house.
I have some 8 relay boards lying around and a few arduino unos.

I am considering 3 ways of doing the connecting.

  1. Attaching both live wires to a relay each and crossing over using the NC connector. Then using software, setting 2 data pins to either high or low at the "same time" to switch.
    This has the disadvantage of losing a data channel per switch, this also has the disadvantage of the actual switching happening 1 instruction later for the second relay ( negligible I would think ).

  2. Same as 1 where the light switch connections are concerned but only using 1 data connection to the arduino but splitting that wire so it is connected to 2 of the relay's input pins.
    Advantage: need less arduinos

  3. Using an external DPDT relay that I switch over using 1 of relay board's relays.
    Disadvantage.. Pretty expensive to buy extra multiway switching din relays. (+- 25€ a piece here)

I'm leaning towards option 1 but would like to get some feedback.
I'm sure you all know what I'm talking about here but I'll gladly draw some pictures of stick men hunting mammoths if needed.

Thnx in advance for any reply.

2

Adding tinkercad circuit designs to show what I mean.
Tinkercad doesn't have 8 relay boards as components so I had to improvise.
First ( in scenario 1 first and second ) switch is to enable/ disable arduino blink.
last and one before last switches are simulating switches around the house.
Last relay shows the arduino the lamp state.

3

Be warned. The PCB is likely not designed to handle 220V (you priced in Euro, so a good bet your have 220V). The relays yes, but not the PCB. I have yet to see a relay board that uses the correct trace and connector to handle 220V without risk of arching.

Fritzing is great for seeing how to connect the items. But it stinks at figuring out what the system does or is supposed to do. A hand drawn block diagram would be 10x better.

4

adwsystems,

Thnx for the reply.

In what I'm doing the other pole will not be connected to the board so arching to it will not be an issue. But still it's worrying. The seller mentions the article handles up to 250v but I believe you when you say that's only for the actual relay.

Also since I'm using leds I can use the 12v circuit instead..

I can also go for my option 3 and use din rail relays that switch on 24V and use the relay board to drive those.

If you still have some pages where I can read up on this issue I would appreciate it.

Friendly regards.

5

Phoenixxl:
I can also go for my option 3 and use din rail relays that switch on 24V and use the relay board to drive those.

This is by far the best way to go.

Even if you only connect one of the 220V poles, you still have more than 200V differential to the other traces.

This link includes basic requirements for current and voltage on a PCB PCB Design Layout Rules