I've been researching info on magnetic card readers but documentation isn't very complete (e.g. Omron V3A-4K). I'll be using a reader in an application where a few AA batteries provide power for > 1 year so I need to keep the reader off until a card needs to be read.
I see many readers have a "card detect" or similar output and a "current save" mode. As best I can tell the card detect output is driven by a FET totem pole and current save mode puts the unit into the 2mA consumption range. If this is true then I don't see how the reader can be used in an ultra-low current application without the user pushing a button before he swipes the card, which is undesirable.
How is this problem typically solved?