.. _label-section-unboxing: Unboxing ======== I'm working with 2 used pHin sensors, obtained recently from a former user on 17/12/2021, following the announcement that the pHin service would shut down on 20/12/2021. After unboxing both units, neither of them were sending out BLE Advertisements. Reading through the `User Manual `_ didn't help much. A bit of googling brought me to pHin's `Setting up your pHin Monitor `_, which mentions that the bottom cap must be removed and swiped over the water drop on the casing in order to activate the device. .. thumbnail:: _images/photos-opening/opening-0.jpg At this point I was assuming there must be a `reed switch `_ under the water drop, connected to other parts of the circuit in any of the following ways. a) a GPIO of the MCU, acting like a user-button b) the reset pin of the MCU c) the enable a power regulator d) to the gate of some transistor, gating the power supply of the MCU The last three options are the most likely: when you're designing a battery-powered device that's completely sealed, having a magnet to power-cycle your chip can be a big help. The reed switch could be useful for activating the device after delivery to the user. The magnet could also be a smart way of saving power while the product is shelved: the monitor could be set in a very low-power mode after factory tests by some special command on a serial port. The magnet could then make the device exit the standby mode and start measuring and advertising over BLE, either through a GPIO interrupt or a power cycle depending on how the reed switch is wired. Swiping both devices with the bottom caps and other types of magnets did not produce the expected result: the LED of neither pHin monitor blinks when a magnet is brought close. Seeing that a magnet had no effect, I concluded that the batteries were dead (which they were, as I observed later when opening the monitors). This leads us sooner than expected to the most thrilling part: the :ref:`label-section-teardown`.