Hobbyists, makers, students and pretty much everyone who works with electronics has encountered the same issue, not having a handy power supply to test their projects. Usually, controllable power supplies are big, expensive and for some people difficult to access, and most small power supplies are not controllable. As a result, Roberto Lo Giacco created Flexipower, a small, portable, flexible, and remotely controllable dual channel power supply.
Flexipower is controlled via a mobile application and its battery operated. It can work up to a voltage of 20 V and a current of 1 A (per channel). Power supply is powered by two cell Li-Ion or Li-Poly batteries which provide 8.4 v when fully charged, to reach higher voltages the battery is fed into a voltage step up circuit, and to get lower voltages the battery is fed into a high current linear voltage regulator. Also, a simple voltage divider along with the 10-bit ADC is used to measure the produced voltage, and adjust accordingly.
Current measuring is done through a 1 Ohm shunt resistor network made by ten 10 Ohm resistors in parallel which results in 1 mV voltage drop per mA. In the case of currents lower than 320mA, the integrated circuit INA219 is used to obtain a very precise reading. When the supplied current goes above the capacity of the INA219 the shunt resistor voltage drop is measured using the 10 bit ADC.
As mentioned before, Flexipower uses 2 rechargeable batteries that are charged via a barrel jack connecting a 12 V source capable of around 1 A. An RGB LED is used to inform the user about the status of the device (power on, battery warning, connection status etc.). The LED is also used to indicate the battery status. Additionally, each channel has a green/red LED to indicate if it is enabled (green), or over current (yellow).
Furthermore, the device can create “Flexipower SSID”, an access point for people to connect and control the power supply. The app was created to avoid using a big LCD screen with limited data logging capabilities. The app allows control, unlimited data logging and visualization just with the use of a smartphone.
For complete specifications, list of materials used, schematics and app download go to official website. The creator always tried to minimize components costs while still providing a lot of capabilities. It still can be improved, but it’s a project that could make the life of people easier. Its important to clarify that this device is not a replacement for benchtop power supplies, but for portability is a great option.