Introduction

If you’ve ever wanted to know exactly how much current your circuit is pulling, how much power your solar panel is delivering, or how healthy your battery pack is in real time, the INA219 is one of the best low-cost ICs for the job. In this project, we’ll build a complete voltage/current/power monitor using the INA219, an Arduino (or ESP32), and a tiny bit of code — and along the way, understand exactly how the chip works under the hood, straight from the datasheet.

For Full Project:

https://electronicsworkshops.com/monitoring-voltage-current-power-with-the-ina219/

What is the INA219?

The INA219 is a digital current shunt and power monitor IC from Texas Instruments, communicating over I2C. Instead of using an analog ammeter or a separate ADC + amplifier circuit, the INA219 does everything internally:

Measures the tiny voltage drop across a shunt resistor (to calculate current)

Measures the bus voltage (the actual supply voltage on the high side)

Internally multiplies current × voltage to give you power — no extra math needed (though you can also calculate it yourself)

Reports everything over I2C as clean digital values

Circuit diagram

In this schematic, current to be measured flows from connector P1 through the 0.1 Ω shunt resistor (R5) and into the INA219’s IN+/IN- pins, which sense the tiny voltage drop across the shunt to calculate current — the VIN+/VIN- test points let you probe this directly. The chip is powered through VCC on pin 4 (VS), with the 100 nF capacitor (C1) decoupling supply noise right at the IC, and GND tied on pin 3.

The A0 and A1 address pins (5 and 6) are pulled to GND through 10 kΩ resistors (R1, R2), setting the I2C address to the default 0x40; they could alternatively be jumpered to VCC for a different address. SDA and SCL (pins 8 and 7) are pulled up to VCC through another pair of 10 kΩ resistors (R3, R4), as required for any I2C bus, then broken out to labeled connectors alongside VCC, VIN+/VIN-, and GND — giving you a clean set of header pins to wire this board into a microcontroller and the circuit you want to monitor.

PCB Files

3D View

Real-World Applications

This exact build can be reused for:

Battery monitoring — track discharge current and remaining capacity on a Li-ion pack

Solar panel logging — measure instantaneous power output across the day

Motor/actuator diagnostics — detect stalls via current spikes

USB power meter — measure how much current a device actually draws

EV / BMS prototyping — INA219-style high-side sensing is the same principle used (at higher voltage/current scale) in real battery management systems

Given your interest in electronics calculators and PCB projects, this also makes a great standalone PCB design exercise — a 2-layer board with the INA219, screw terminals for VIN+/VIN-, an I2C header, and silkscreened pinouts would be a clean, practical PCBWay-style project to document and showcase.

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Conclusion

The INA219 turns what used to be a multi-component analog measurement circuit (op-amp + shunt + ADC + math) into a single, accurate, I2C-addressable chip. With under $5 in parts and 20 lines of code, you get real-time voltage, current, and power readings — accurate enough for serious projects like solar logging, battery monitoring, or power-budgeting an embedded system.

From here, natural next steps are logging the data to an SD card, streaming it to a web dashboard over WiFi (ESP32), or even feeding it into a closed-loop control system that throttles a load based on real-time power draw.