Choosing between relays and MOSFET driving multiple loads

Question

I am working on a project, which may eventually be used commercially, so I want to ensure that it is safe.

It has a 80Amp 12v power supply. It is controlled by a touch screen, with switches to control different systems.

It needs to control 4 separate LED panels, each of which draw 7.2 Amps. It needs to control 6 linear actuators. 4 of the actuators can be tied together, and draw 5 Amps each. 2 of the actuators can be tied together, and draw 4 amps each.

LED Zone 1-4: 4 @ 7.2A each, 28.8A total

Actuator Zone 1: 4 @ 5A each, 20A total

Actuator Zone 2: 2 @ 4A each, 8A total

Total: 56.8A

For this project, I see two main options, component wise. I could either use SSRs, or MOSFETs to drive the LEDs/actuators.

I also could have a separate MOSFET/SSR to drive the 6 actuators, and tie them together in software, or, two MOSFETs/SSRs to drive the two groups together.

Which approach would you recommend, and why?

Also, since this is my first time with this high of current loads, i'm not sure on fuses. Should each bank of MOSFETs/SSRs have its own fuse?

Answer 1

You want either MOSFETs or mechanical relays. Solid state relays usually have too high a voltage drop to be suitable at these currents. There are solid state relays that use MOSFETs as the switching element. However, since you don't seem to need the isolation, it's probably easier to use MOSFETs directly.

Switch as many loads separately as you can. That reduces the maximum current any one FET needs to be able to handle. You can then choose to switch several loads together if you like. Minimize the maximum current each switch needs to deal with.

Low side switches will be simpler, if it is OK to keep the + input to all loads permanently connected they don't need to have a common ground when off.