Methods, systems, and apparatus, for conserving power in a system, comprising: (a) receiving a card interaction from a card at a card interface of the system, where the system comprises components including: a microcontroller, one or more card interfaces, a power source, an antenna, and a wake-up circuit, where the components are powered down, and where the card interaction triggers the wake-up circuit; (b) activating a power source using a signal from the wake-up circuit; (c) powering the microcontroller using the power source and in response to powering the microcontroller: (i) powering down the wake-up circuit; (ii) powering up the card and the respective card interface associated with the card interaction; (iii) receiving card data from the card through the card interface; (iv) powering down the card and the respective card interface; (v) powering up the antenna; and (vi) sending the card data using the antenna.