Contrary to the other smartDevices, the smartMeter is an autonomous device. It doesn't require any connection to the RoboTX controller as it features its own display.
Large fischertechnik models include many motors and lamps and reach high power consumption. A simple bulb lamp requires up to ~100 mA and 1 W.
So total consumption can quickly outreach the capacity supplied by the battery pack or the AC power adaptor.
This project provides a handy tool to get precise measures:
The smartMeter keeps minima and maxima for each of the three measures. A push-button allows to change unit, clear the minima and maxima, and change the decimal separator between point and comma.
As usual, the module is cased on a 9V red box for a nice integration.
The different screens, from left to right: splash screen, measures in mV-mA-mW, measures in V-A-W with point and comma as decimal separator.
Selecting the function with the push button, from left to right: ./m. change of units, =0 reset, ., decimal separator, __ cancel.
The smartMeter uses an INA219 as sensor and a MSP430 as MCU. The project is described at the Embedded Computing website.
Thanks to its built-in regulator, the smartMeter can be powered with 5–16 V. The measure range is wide enough for fischertechnik models, up to 26 V and 3 A.
The I²C Voltage-Current-Power INA219 Sensor provides the three measures, so there's no need for multiplying voltage by current to obtain power.