Page 153 - Programming the Photon Getting Started With the Internet of Things

Power Shield

The power shield does exactly that—it allows you to power your Photon from other power
sources than USB. The shield has an intelligent battery charger and power management
unit, along with a wide-range input voltage regulator and an (inter-IC) I2C-based power

gauge. You can power a Photon with either a USB plug or a DC power supply from
anywhere between 7 and 20 V DC and can also charge a 3.7-V lithium ion–polymer
(LiPo) battery at the same time. This is the perfect companion to your Photon board,
giving you the ability to truly create mobile applications from anywhere in the world. The

power shield is shown in Figure 7.6.

Figure 7.6 Particle power shield.

The power shield system switches between the different power sources automatically,
reducing the charge and discharge cycle stress on the battery. The fuel gauge allows you to
easily monitor the battery’s state of charge, allowing it to notify the user remotely over the

Internet and take the necessary actions when needed. The shield is also set up so that when
powered from a USB port as well as a DC power source, the shield will automatically
choose the DC source over USB. The charge current is set to 500 mA when charging from
USB and it is set to 1 A when charging from a DC power source.

The Internet Button

The Internet button is a great way to get started with the Internet of Things by creating