A low-cost, real-time DC power monitor built for ham radio operators who want to keep an eye on their station's current draw, voltage, and power consumption. Built around the INA226 bi-directional current sensor, an Arduino bridge, and a Python GUI with live graphs — or run it fully standalone on an Arduino Nano with an OLED display.
- Monitor transceiver current draw during TX vs RX — catch excessive draw on transmit
- Track voltage sag under load — identify weak power supplies or undersized wiring
- Calculate real power (W) — know exactly how hard your station is working
- Relative (zero) mode — zero out resting current and see only the TX delta
- Log to CSV — record a contact session and review power usage later
- Standalone OLED mode — mount near your rig with no PC required
- Handles up to 50A continuous — suitable for most HF rigs (100W class draws ~20A @ 13.8V)
| Mode | Hardware | Best For |
|---|---|---|
| Standalone OLED | Nano + INA226 + SSD1306 | Permanent shack install, no PC |
| PC GUI | Any Arduino + INA226 + Windows PC | Logging, graphs, detailed analysis |
| PC CLI | Any Arduino + INA226 + Windows PC | Quick terminal readout |
| Qty | Item | Notes |
|---|---|---|
| 1 | Arduino Nano or Leonardo | Nano for standalone, Leonardo for GUI |
| 1 | HiLetgo INA226 Module | I2C, bi-directional, address 0x40 |
| 1 | 75mV / 50A Shunt Resistor | Antrader 2-Pack 50A 75mV DC Current Measuring Shunt Resistor (Amazon) — inline on the positive DC feed |
| 1 | SSD1306 0.96" OLED (optional) | Standalone Nano mode only |
| — | DC wiring, terminals, enclosure | To suit your shack installation |
The INA226 shunt goes in series on the positive DC line between your power supply and your rig:
[PSU +13.8V] ----> [INA226 V+] ----> [INA226 V-] ----> [Radio +]
[PSU GND] ------------------------------------------------> [Radio GND]
The Arduino connects to the INA226 over I2C (two wires). Everything runs off USB power from a phone charger or the shack PC.
Requires Python 3 and the following packages:
pip install -r requirements.txtRun:
python software/gui.pyA port selector dialog appears on launch. Select your Arduino's COM port and click OK.
- Live voltage, current, and power meters (large display)
- Scrolling graphs for voltage, current, and power (last 30 seconds)
- Min / Max / Average current and peak power stats
- Relative (Zero) mode — zeroes out resting draw so you only see TX increase
- CSV logging — timestamped log file, toggle on/off with one button
Flash firmware/amp_meter_nano/amp_meter_nano.ino to the Nano.
See docs/nano_manual.md for full wiring and setup instructions.
Display shows:
50A POWER MONITOR
─────────────────────
V 13.82V
I 18.543A
W 255.36W
No PC required. Powered from any USB charger.
| Situation | Expected |
|---|---|
| Rig on, RX idle (100W HF) | 1–3A @ 13.8V |
| Rig TX at 100W output | 18–22A @ 13.8V |
| Rig TX at 50W output | 10–12A @ 13.8V |
| Linear amplifier in use | 30–50A depending on power level |
Pre-configured for a 75mV / 50A shunt (R = 0.0015 Ω).
If you use a different shunt, update this line in the .ino sketch:
ina226.setResistorRange(0.0015, 80.0); // (shunt_ohms, max_amps)amp_meter/
├── README.md
├── LICENSE
├── requirements.txt
├── firmware/
│ ├── amp_meter_leo/
│ │ └── amp_meter_leo.ino # Arduino sketch — Leonardo
│ └── amp_meter_nano/
│ └── amp_meter_nano.ino # Arduino sketch — Nano + OLED
├── software/
│ ├── gui.py # PyQt5 GUI with live graphs (Leonardo)
│ ├── cli_leo.py # CLI terminal monitor (Leonardo)
│ └── cli_nano.py # CLI terminal monitor (Nano)
└── docs/
└── nano_manual.md # Full Nano wiring and setup guide
GNU General Public License v3.0 — free to use, modify, and share. Any derivative works must also be released under GPL v3. 73 de the author.