First post here. I received and installed my Konnected 12 zone setup this week but I am unsure on the power requirements for Amazon Fire tablets. I went through as many forum posts as I could find and did not really know if the question I have was answered.
I have two existing keypads that I will be removing and using the 12v to 5v adapter to power Amazon Fire 7 tablets. It is my understanding that trying to power both of these tablets using the Konnected board terminals would overload them. I did purchase 1 - DC Power Screw Terminal Adapter and I have one extra DC power adapter.
Would I be able to place both sets of wires coming from the panels into a single dc power screw adapter and then use a single power adapter to power both tablets? I am unsure if two tablets on 1 DC power adapter would not work and/or cause any problems.
Two Fire tablets will probably draw 1 A, 12 V at most. The Fire HD 8 comes with a 1 A, 5 V charger. 2 A * 5 V = 833 mA * 12 V. I'd plan for up to 1 A at 12 V, just in case. Most of the time, you'll actually be pulling very little current, since they will fully charged.
If you use that screw terminal adapter, the tablets would be connected in parallel with the konnected board, meaning current (Amps) add. So with a 2 A max power supply, that would leave ~1 A max for the konnected board. You just need to be sure you aren't pulling a lot of current off the Aux 12 V or siren all the time.
I think you'll be fine doing exactly that.
Personally, I wanted lots of spare capacity, so I got a 12 V, 10 A DC power supply. I run three tablets and a dual siren (30 W = 2.5 A @ 12 V) from that. Right now I'm only using up to 4 A max load, so I could also power the konnected board (and future devices!), but it's still using the supplied 12 V adapter.
These calculations are based on everything pulling max current at once, which is unlikely. I think sirens are the biggest concern, since they tend to draw > 1 A.
Wow! Thank you for the in depth and informative response. I really appreciate it. My system is now up and working great.