Yes, the one you linked is fine but here is a the same one.
You saw this , right ?
Same problem here
Finally I replaced PCF8574 & co by a single arduino pro mini working as a slave TWI device to drive my relay board.
Maybe overkill, but still cheap, easier to wire, and allows any custom drive (initial values, secure minimum time between switches, ...).
How much experience do you have with electronics ?
You are a "kludger". Instead of starting with a blank sheet of paper and listing your design criteria and then selecting the appropriate components and then designing the box based on the physical and electrical characteristics of the components, you looked around your garage for some piecd of junk and said to yourself "Let's see, I want to control AC devices so what I want is a smsrt power strip so why don't I use a power strip ?". If you strar from scratch with 6 SSRs , your first task is designing the heat sink. If you look, you might find a 1.5" x15" 18" strip of finned heatsink material The aluminum base is 1/8th " to 3/8th" thick with the fins running lengthwise . The fin height can be anything from 1/2" to 3/4" tall. The width has to match the heatsink dimensions. You drill and tap the base plate mounting holes fof the SSRs. If the base is at least 1/2" thick you can drill and tap the cover mounting holes on the sides.
Here is something similar . This heat sink is 3.93 x 2.00 x 0.90 inches and is of course too small but gives you an idea what I was talking about. This company appears to specialize in the kind of heat sink I am talking about. You can see a long strip in the photo. The label for the long strip says 6pk/12pk , which appears to imply the long strip comes in two sizes, one for 6 SSRs (what you need) and another for 12 SSRs.
I haven't found any yet but here is a different style of SSR heatsink.
SSR HEATSINK
Here is a 40A SSR mounted on a heatsink for about $10
I don't know what kind of outlets you need (US or foriegn,) but if you are in the USA, the single outlets are such that the power strip box would have to be much wider than a normal power strip because the outlets would have to mount across the strip. (side to side)
single outlet
On the other hand using pull-down resistors at the output of PCF8574 instead, is not an option since the PCF8574 would then be unable to drive the outputs high due its the low driving current capabilities.
Are you sure about this ? Did you try 20k and 10k pullups//pulldowns ?
I also just realized after reading that if I get a 5amp module, it can handle only 3.5amp rms current, as 5amp would be peak current
I seriously doubt that. The value the product is marketed as is almost always the rms current , not the peak (which is SQR(2) +rms) If it's an AC module, marketed as 5A, that's the rms rating, almost for certain.
From Sparkfun page
The ACS712 current sensor measures up to 5A of DC or AC current.
I can't find anything to prove it but I don't think hall effect current sensors sens instantaneous current because they are based on magnetic fields which are the result of rms current.