Driving 24VDC DIN bistable (impulse) relay by Arduino

Projects Discussion and Showcase Home Automation
1

When I was doing reconstruction of electrical network in my appartement, I did it with possible future home automation in mind. Because of that, all my lights are driven by DIN impulse (bistable) relays from EATON. They are driven by 24VDC from DIN switching power supply.

I started with development of a board with Arduino Nano that would act as a "smart switch" and will be sending same 24VDC impulses to the relays as when I hit real switch on the wall.

My question is, what should I use as a switching component? I totally ditched use of a normal relay as I think thats not needed for 24VDC and around 7W of power that the DIN relay needs to flip the state. I was looking into SSR relays, but I think that because it is DC, I can go just with normal MOSFET? Is that feasable?
I was thinking about something like IRLML6344 as it is logic gate mosfet and 30V/5A seems enough.

  • Not sure if I can drive it directly from GPIO or I need e.g. resistor in front of the MOSFET?
  • Also, my concern is the possible inductance kickback from the relay. Is that a thing in this type of DIN relays?
  • One more concern is about shared ground reference. Is it ok for the Arduino board to share ground with the relay's power supply? Even if they will be two different DIN rail power supplies?
2

Post the datasheet and we will see?

3

It is this one: Datasheet - Z-S48/SS
but they are not really saying much about the driving circuit itself.

4

If you don't want to solder a bunch of components together you can use one of these modules to activate the relay

They are available in many places

5

I will be making PCB with all components on it. I preffer small size and to be able to get components placed by JLCPCB so I want SMD MOSFETS if possible. The 400W modules are crazy overkill for switching 7W momentarily.

6

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7

Yes, I know the basics of this. I am asking if I need the flyback diode for this type of DIN relay switching and what is the best SMD MOSFET for this purpose.

8

No flyback needed.
IRLML6344 is fine.
What do you mean by best, cheapest, smallest, type of package?

9

Are you sure about the flyback? How I can know that the DIN relay is not driving the load directly? I would probably need to hook up scope to check that right?

By best I mean best for this usecase and something that JLCPCB have in their part list at JLCPCB Assembly Parts Library & Component Sourcing - JLCPCB

10

The control signal can be 24V AC or DC so there must be rectifier diodes inside.
You can put a small 40V 1A diode across A1 and A2 just in case, cathode connects to A1

I don't use parts from JLCPCB you will have to do your own searching.