Check out this guide on batteries for more great information. If you observe the millamp-hours of current used by a device you can compare it to the milliamp-hour capacities of batteries and estimate the battery life of the device. This is a very useful measurement to understand the battery life of a device since batteries are measured in amp-hours (or more typically milliamp-hours). To start the amp-hours will be around 0, but over time they will grow based on how much current a device uses. The amp-hour measurement is interesting because it's showing how much current has been consumed by the device since the power meter was turned on. For the LED you might see values to start like: Watts & Amp-hours - This mode shows the power at the top in watts (or milliwatts), and the observed amp-hours (or milliamp-hours) since the power meter has been powered on.For example for an LED and 4 batteries you might see: Volts & Amps - This mode shows the volts (or millivolts) of the power supply at the top, and the current consumed by the device in amps (or milliamps) at the bottom.

Every 5 seconds the display will change to show a new set of values, and in total there are 4 values that are displayed: You should see the meter display different power measurements. Make sure the power meter's Pro Trinket has power too as it will not power itself from the measured device's power source (you can instead plug in the Pro Trinket's micro USB connector to a power supply/computer, or even power it with batteries). Try wiring up a LED and battery as shown, then turn on the power to the batteries. This allows the power meter to read the voltage from the batteries.įinally to complete the circuit a small resistor (~560 ohm) is connected from the cathode (shorter leg) of the LED to battery ground. In addition to being in series with the LED a wire connects the battery ground to the power meter ground. In this way the INA219 is in series with the power to the LED and it can measure how much current is consumed by the LED. Then the Vin- connection on the INA219 is connected to the anode (longer leg) of the LED. In this diagram a small battery holder (4x AA) has its positive power output connected to the Vin+ connection on the INA219.

Adafruit trinket 5v power ma