The chip, which is designed as a relay driver, places a diode across each relay that the chip drives. When a relay releases, since it is an inductor, stored energy gets released as a pulse. The diode forces that pulse back through the relay coil instead of the electrical system.
Transient suppression is an art. In one case there is prevention and the other case there is suppression of known causes.
A lighting strike to a home power line is rare, but it will take out many things in the home. The cost to install a whole hose surge suppressor might exceed $1000 USD whereas a ISOBAR surge suppressor will cost about $100 USD and comes with at least a $50,000 USD connected equipment warranty. It's not worth buying a surge suppressor without a warranty.
This is also something you should consider:
https://canada.newark.com/multicomp...rd Terminal Blocks&MER=PPSO_N_P_Standard_None
and this:
https://canada.newark.com/vector-el...lar Products&MER=PPSO_N_C_EverywhereElse_None
and a small case and grommets.
These:
https://canada.newark.com/vector-electronics/t42-1-c/terminal-push-in-pcb/dp/38F1363 make life easier, but are not essential. The insertion tool is quite pricey, but you don't need it.
This wire:
https://canada.newark.com/ok-indust...lar Products&MER=PPSO_N_C_EverywhereElse_None It's not essential, but the dispenser contains a cutter and stripper which is really convenient. Nonetheless, you need some sort of solid wire, like 22 AWG or smaller to make connections. Multiple colors, again, add to the cost of one.
Newark doesn't have a machined pin DIP socket, but this
**broken link removed** can work. You have to cut it into two 8 pin sections. From experience, you normally loose one position.
So, while I'm at it, you may also need spacers or standoffs for the PCB. A hardware store may be aa source for a few unless the box contains them. Most of the time you have to buy 100 screws for the boxes.
Even for a simple project, the complexity adds up. The case, power supply, real estate (the PCB itself) and connectors add up quickly.
What about mounting? You can purchase flange mounted cases. I like these guys:
https://www.polycase.com/index?
You should make sure it works first, but it should.