Normally every house has power usage meter where you can see how much power you have used. But sometimes you might want to see how much energy you are currently using and probably trace the devices that are most energy hungry. John decided to instal energy meter next to his power meter. He didn’t want to use LCDs or LED indicators that wouldn’t look great next to meter blown glass face. So he went with Nixie tubes. He used couple of ready made nixie tube modules that already accept 5V and can be controlled via SPI interface.
He paired Arduino with ESP8266 module to have good ADC and IoT functionality. He found out that Nixie tubes draw quite some power – 300mA. So he went with only two modules to reduce the overall impact. He made unit indicator that would allow indicating from 0 to 100MW. Only two significant figures are always visible. This is more than enough for rough monitoring. Power is measured with SCT-013 clip-on current transformer which has current sensing resistor. Arduino samples the output and calculates the power usage by applying power formula P=V*I. Panel meter streams data through WiFi that in future might be used to store in to database and display rolling usage graphs. There is possibility to tweak RGB backlights remotely as well.