Chen Liang's Power Meter Tracks Your Project's Energy Hunger with Just Three Parts

Maker Chen Liang is back with another useful tool built from a minimum of components — this time turning a Digispark ATtiny85 development board, current sensor, and LED into a breadboard-friendly power monitor.

"[A] Power Monitor is useful to visualize the power usage of your circuit. Especially the portable gadgets powered by a battery, the power usage determine the battery life," Liang explains. "A power monitor can help you locate the power usage of your circuit or program and then help you decide the battery capacity is required in your project. Even minor modifications can significantly impact power consumption. For example […] adding a resistor can drastically reduce the power consumption of an LED. Without this intermediate resistor, a color-changing LED could consume over 100mA."

The heart of Liang's latest build, which follows last month's release of a two-component dual-band Wi-Fi spectrum analyzer, is the Digispark — an Arduino-compatible development board built around Microchip's ATtiny85 AVR microcontroller. This is linked to two breakout boards: one for Texas Instruments INA219 current sensor and the other an SSD1306-based OLED single-color display.

"You can see four metrics, two line charts and one area chart on the OLED display," Liang explains of the device's usage. "The first line chart represent the voltage, the second line chart represent the current in mA and the area chart represent the power usage in mW. And also the mWh and time metrics help to count the accumulated power usage. The program read values from the sensor continuously, so you can monitor the live power usage."

The project is documented in full, including source code, on Instructables.