Hey everyone, it's been a while. Hope you're all doing well. Today I want to show you some more watch related stuff I've been working on.

- Download Source Files


I've already shown you the polarizer mod which inverts the display, making it black, but I always wanted a good way to change the display to other colors, and I've been experimenting for a long time on how to do just that.

One day I decided to see what the kapton tape I use for my 3D printer bed looks like when applied to the display, and to my surprise it turned out great, transforming the boring regular LCD into a nice amber color.

I then started searching for other polyimide-like tapes in different colors and found a few. From my experiments, anything around 20 microns or thinner could potentially work.

One really cool thing is you can combine some of the different tapes over each other to create a new color. For example the amber + blue tapes create a really vibrant green display. I've found this only works for really thin tapes though.

So far I have managed to change the display into a range of colors, including, amber, blue, pink, red and green.

To get the effect you need to apply the tape to the LCD glass. It can be tricky, and I use a plastic credit card to smooth the tape as it's stuck down. This removes any air bubbles.


Another interesting mod is to make the screen transparent. To do this, you need to remove the reflective foil that's glued to the back of the LCD glass. I did this using a sharp knife and some adhesive remover. You then replace it with polarizing film, so there are polarizers on both sizes of the glass.

You also need to paint the inside of the watch PCB white, since if you don't there won't be enough contrast between the display and the insides to read the numbers. I used simple enamel touch-up paint with built in brush.

Be sure to only cover the area shown, avoiding the various contacts required for the watch to still function.

The final effect, when paired with the F-91W variant which has a transparent strap is definitely unique. I changed the LED to a white one, so When you use the LED in the dark, the light illuminates the entire space below the glass.


I have updated the micro SD socket add on too, so it's now completely standalone from the backplate and can be attached easily using 4 x M1.4x6MM screws.

The middle of the 3D printed frame is intentionally thin, and bends over the internals of the watch, providing just enough room to fit the socket inside. It's definitely handy to have a backup memory card on you just in case you need it, especially with micro SD card storage capacity now being up in terabytes.

One thing to note. When you're attaching this, remember to bend the contacts from the watch upwards, so they touch the inside of the metal backplate. This is the piezo which creates the watches beeping sound.


The strap mechanism on the F91W isn't the regular spring loaded type you find on most watches, and can be a bit of a pain to remove by hand, so I figured I'd 3D print a tool to simplify the process.

It basically involves disassembling two cheap generic bracelet link removers, and inserting them into a custom 3D printed jig. The threaded pins are held in place by two 5mm square nuts.

To remove the strap you just place the watch in the jig, with the threaded pins on the right side. Then you slowly turn the screw and this will pop the friction pins out of the strap.

To replace the strap, you simply add the straps and pins to the watch body as shown. Make sure the pins are hanging out a little on the left side, then place the watch into the jig, this time with the threaded pins on the left side. You can use the screws to push the strap pins so they're secured to the watch body.

If you're gonna replace the strap with a non Casio one, it might use a spring loaded pin instead of a friction one, so follow the instructions from the strap maker instead of using this jig.


I found a mod on Instructables which shows you how to add a second LED to the F91W, and I tried creating a simple flex PCB to make the process easier. It was so simple infact that I messed it up because I wasn't paying attention before I sent it off to the manufacturer.

Anyways, after correcting the mistake, the mod does work, but I'm not sure why it makes the watch so unstable. Sometimes it works fine, and others it keeps resetting or turning the display off. I'm guessing the Casio chip inside does not like the changes in power consumption with that second LED. Gotta admit it looks really nice in the dark though.

I also tried a couple different NFC antenna designs with flex PCBs so that I could install it inside the watch body without removing the frontplate. Unfortunately there just wasn't enough room to make the antenna strong enough, but perhaps there are other solutions I haven't thought of yet.


If you'd like to make your own stuff, source files etc are at the top of the page, or if you'd like to buy a pre-modded watch, or any of the tools I mentioned in the video, check out the NODE shop.

I've also been getting more into modding analog watches too, and have created a few minimalist watchface mods for the Casio MQ24, which is basically the analog equivalent of the F91W. I'm interested to see what else is possible with these.