Please forgive in advance that I'm mostly a software dude and a tinkerer... Electronics aren't usually my thing.
I have these two paired products (and similar products are available elsewhere):
I am using this to lock and unlock 5 different vehicles, which also have a Unos for other reasons.
My problem is with providing an appropriate power supply.
I would like the key fob to power up the Uno upon unlocking doors, which means I'd like to supply the receiver from something other than the Uno at the "+5V" pin. Currently available I have a nicely regulated 9V supply from a small DC-DC converter (which otherwise becomes the power supply for the Uno). But for greater simplicity, I would prefer to use my vehicle's operating voltage. (Which I know isn't really 12V, but as much as 14.5 "noisy" volts.)
As far as I know there's no documentation for the receiver. Surely it has a voltage range, but what is it?
The Adafruit page only says it's "based on the PT2262", and the spec sheet for that IC says it can operate from 4-15 volts... BUT... I don't know if that applies to the whole board or just the IC.
AND, importantly... Even if it can tolerate more voltage, the outputs can't be more than 5V because I need it to provide a logical high/low direct to the Uno pins.
So, can this work? And if so, will the outputs still be no higher voltage than the Uno can take? (5V I believe.)
On a related question: All of these questions are moot if it is practical to keep my Uno powered constantly and use its own 5V supply. But how much current would the receiver unit plus the Uno draw? I'm thinking the vehicle battery is much less likely to die if only the receiver is powered. But if keeping the Uno always on requires negligible current, please tell me and that'll be my solution.
P.S. Recently I have been "challenged on my judgement" for using these units to lock vehicles: Yes, I am keeping the vehicles secure in other ways and I'm using one of the 6500 randomly-selected codes, matching remote and receiver codes.