Many UK houses have electronic meters for measuring electricity consumption. Most of these have an LED that flashes when a given quantity of energy has been consumed.
In the UK most meters have LED outputs which flash once for every 1Wh. They will flash 1000 times for each kilo-watt-hour (1 kWh). If a sensor is used to detect the pulses of the LED then it is possible to track electricity usage.
Which sensor?
The meters have red LEDs with perhaps a slight orange hue so the selection of the sensor should be matched to the spectral output of the LED (2).
The TSL261(5) sensor has been suggested as appropriate and some simple designs have been published (3). However the TSL261 is an infra-red sensor with a narrow spectral response centred at 940nm. Given the visible spectrum is about 390nm – 700nm (1) it is unlikely the TSL261 is the best choice.
The TSL251(4) is described as a light sensor. While its spectral response starts at 1100nm (in the near infrared 750nm – 1400nm) and peaks at 750nm it has useful response through the visible range. Its data sheet gives irradiance responsivity figures at 635nm and 880nm.
References and links
- Visible spectrum – https://en.wikipedia.org/wiki/Visible_spectrum
- Red LED spectral output is between 620nm – 645nm for red and 610nm – 620nm for red-orage – https://en.wikipedia.org/wiki/Light-emitting_diode
- Arduino implementation – https://jonarcher.info/2014/03/arduino-based-electricity-monitor/
- TSL251 Datasheet
- TSL261 Datasheet