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Verify your light use case

Changing the world with light cell film

Thursday 12 September


Epishine’s product is a power generating light cell film which can prolong the lifetime of, or even replace batteries in low energy devices using indoor light.

Epishine needed help to explain their product to their customers, who are mainly product designers of wireless sensors e.g. thermometers, or magnetic alarm switches for windows.

The challenge was to help the customer explore the concept of indoor luminance themselves and learn about it’s possibilities as well as it’s limitations.


Together with Epishine, we discussed how to best help the potential customer to familiarize themselves with light cell film, and ended up with a mobile app that

  • uses the builtin camera to measure the luminance on location
  • shows best practices on how to make the most of the indoor light available
  • as well as a simple tool calculating the area of light cell film needed, given the power requirements of the device and the measured luminance.

As technological stack, we chose iOS and Swift 5.

To be able to parallelize the work, we split it into creating the light meter, presenting the results of the calculation and the guides. We managed to captured the mobile camera stream and produced a rough luminance value in lux (lx), and present it in just four days.


When prototyping an app which depends on native APIs and having a fairly simple user interfance, it’s a good idea to limit yourself to one platform (in this case iOS).

We also learn that measuring luminance is trick. The best way, of course, is to use a dedicated instrument. But by using some tricks such as putting a white sheet of paper at the spot to investigate, and then measuring the amount of reflected light, we could approximate the luminance well enough.


We managed to deliver an iOS app, with which Epishine will be able help potential customers explore the use case powering their products with of indoor light.