Living The Dream: New PCB For A Dirt-Cheap Calculator Watch

Well, this hack has us tickled pink. We love the idea of buying some really cheap piece of technology and doing something amazing with it, and this is a textbook example of that. [davedarko] found the cutest little calculator watch on Ali Express and is working on making a new PCB for it. The plan is to use an ARM processor and Arduino and add a few extras like 24-hour mode and a pink (or potentially RGB) backlight. The new brain will be an ATSAML22G18A, which has an on-board LCD controller and exactly one I/O pin to spare without charlieplexing the buttons.

One of [davedarko]’s primary goals is to keep the LCD and figure out how to talk to it. The first order of business was reverse engineering the watch’s LCD controller by sussing out the secrets from beneath the black blob of epoxy. This was an eye-opening experience as [davedarko] had never worked directly with LCDs before. A strange reading made him bust out the oscilloscope. Long-ish and informative story short, [davedarko] found out that it uses a bias of 1/2 for generating the wave necessary to multiplex the segments and keep the signal alternating. This is definitely one to watch!

We love timepieces around here and have seen all kinds of hacks, especially on Casio watches. Want dark mode? Done. Enable the hidden countdown timer? We’ve got that, too. And have you ever wondered just how water-resistant the F91W is?

6 thoughts on “Living The Dream: New PCB For A Dirt-Cheap Calculator Watch

  1. I have the same fascination for LC displays, I’ve even managed to get a 30 year old lcd I salvaged from a radio dumped in a ditch. The LCD was still ok but I didn’t know how to drive it so it sat in my parts bin for 25 years. I got a PIC microcontroller with LCD drivers, like the OP, and tried to get the correct signals. After a few hours I got it working ok! Same with a remote control display and some other stuff. This is great for very low power applications, you can control the display yourself without any external hardware making it really compact.
    Some zebra strips, a little bit of 3D printing and a custom PCD goes a long way connecting to the fragile vapor edged tracks on the glass substrate.Fun stuff!

  2. I am still waiting for a cheap LC smart watch that looks as good as my cheapo casio ae-1200. I don’t want a full color touch display, or an array of sensors. I just want a watch that can show scrolling notifications from my phone like caller ID, my schedule updates, and email subject lines. And a regular button-cell battery over something I have to charge would be ideal, even if I had to replace the battery every year. Something like this looks really close.

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