Techo-Junk: An Electronic Slate

I bought a little LCD slate from Lidl: A5 size and only EUR 8. You can buy similar things for a slightly lower price direct from China (I've seen EUR 6, but with EUR 7 delivery!), but with such a low starting price it is hard to get much lower before the supplier would have to pay you to accept it. Very simple, like an Etch-a-Sketch (good heavens! Those are still being made.), or really more like one of the things with waxy paper and a clear front. You write on it with a stylus and it is powered by a button cell.

I was intrigued by how it worked, so I did a few experiments which I thought I would share with you. The stylus is not special, any similar object will do, like a ball-point pen or even a finger nail. The writing process does not require power. You can still write with the battery removed. However, writing seems to involve some "point effect": touching with the point of a ball-point pen even while not writing will sometimes produce a mark, but pressing with a fingertip or thumb will not, even if I press quite firmly. Erasure, absolutely does require power. You press a button which erases the whole screen and there is a switch which inhibits the erase function. Naturally the erase function does not work  with the battery removed. I've made an executive decision to leave erase enabled: the screen is not over-sensitive and a slider switch is likely to be the first moving component to fail.

My conclusions: the screen is not "point addressable" (there would be no point) and the writing effect is achieved either by pressure or by capacitance. I think it is capacitance. I'm afraid I can see no way of subverting it to some other use (either as an input or an output device. 

Within its limitations it's effective but not really much better than a tiny whiteboard or blackboard. It is designed so that the stylus can be used to provide a stand (but I already have a wire stand I use instead). The slate does come with integral magnets, so you can use it as a large fridge magnet. I find it handy as a supplement to my other To-Do aids and memory joggers.