DIY "Digital" Watch

DIY "Digital" Watch

OK, it's digital in that it's made of bits. From ebay. It's actually mechanical and uses a movement, case and strap from ebay and a couple of 3D printed movement rings to hold it all in the case. The current setup is this:

I bought really cheap parts, and had a few adventures along the way but I have finally got somewhere. I started by buying a Chinese movement that might be based on the ETA 2824, or not. I also bout a case which is better than I thought it would be, and a bracelet. I also bought some hands to fit on the movement. For some reason that I can't remember I part dismantled the movement, I can't remember why. There must have been a reason as I intended to just fit the movement in the case. Anyway, in the process I managed to shear a screw (left and thread, I though they were marked with three slots?) and lose a click spring. I have subsequently managed to make a click spring and replace the sheared off screw with a new one, and the movement works again.

While I was wondering if I'd ever fix the movement I bought another one (even cheaper than the first), as a replacement for the broken one. It was about £11 on ebay and I found out that that isn't really enough money to make a decent movement. The move expensive movement was £22 and that does seem to be enough, just). The cannon pinion never worked properly and the movement kept awful time, simply because the minute and hour hands weren't moving. I eventually gave up on this movement, I may have another go at getting it to work sometime.

At the same time as buying the second movement I bought a correct sized dial, which was very nice. Unfortunately the dial doesn't fit the dial mount on the first movement so I can't use it. I may get another one if I feel like it.

The dial is held in the case with a 3D printed ring, you can see it in the photo above. The movement is also held in place with a 3D printed ring. The case has a clear back, which I didn't deliberately look for, but turned out to be useful when I was sizing and adjusting 3D printed parts:

The movement is automatic, so should and does appear to wind itself.

So, this is an alternative to the digital watches I've been trying to make, and stalled on for the time being, it tells the time, doesn't need batteries and shows the date. That covers most of what I want it to do.

Latest OLED Watches

The latest iterations of the OLED watch are finally approaching wearable. Well, the first of the two is wearable but a bit thick. The second is much more wearable size.

The first iteration is the smallest PCB so far fitted into a 3D printed case and mounted on a cloth strap latched with velcro.

The switches are mounted on the top and the clear front flexes when they are pressed.

The overall thickness is 15mm, which is a bit too thick to wear comfortably. It gets caught on sleeves and catches easily on fabric.


The latest iteration is a one that doesn't use a PCB. This removes 1.6mm of thickness immediately, but makes the construction more manual.

The wiring is manually laid out and not very tidy. the thickness is much less, at 9mm, or 10mm to the tops of the front cover screws. Compared to my main watch this is very similar.

The components are mounted in a 3D printed frame like this earlier version:

The minimum thickness is fixed by the switches that I have used. The wiring adds a millimetre or so to the thickness, that could be reduced by inlaying the wires into the frame. More use could also be made of the 3D space in the frame. At the moment there are no components on top of components.

Using a PLA 3D printed frame is useful as it is possible to heat components and wiring up with a soldering iron and push it into the PLA. This then holds the component firm when the plastic cools.

There may be a better way to wire the components, maybe using a smaller PCB that just has the surface mount components on it.

Watch V6 (With Pogos)

The latest iteration of the watch uses a smaller OLED display I found on ebay. Due to the problems and size of the USB socket I used on previous watches I have gone with pogo pins on this version. This means a jig is required, this is done with stacked PCBs in this case. A cutout allows the PCB to fit into the jig when the pogos re used. The pogos have the programming interface, which includes power for charging the battery.

The PCB fits well in the jig:

I used gcode to cut the rectangle in the top and second PCBs in the stack.

The second PCB has a slightly smaller cutout so the PCB doesn't just fall through the top PCB.

The pogo pins are at just the right height to press on pads on the bottom side of the watch PCB.

The PCB when populated is quite small:

This is the first PCB, which had a few mistakes. I've fixed these in a later PCB. The new PIC (16F1829) has a way to measure the battery voltage with no external voltage divider, so a couple of resistors can be removed form the layout. This PIC also has a larger amount of RAM and flash, and may also be able to measure temperature with no external components.

Watch

I have to send my watch off every four or five years and am then left with no watch for a while. In the spirit of other making, I've decided to have a go at a watch of my own.

This is a breadboarded circuit using the 40 pin DIP chip. I bought a few of the DIP versions as they are much better for prototyping, I don't want to have to build a PCB at this stage.

The OLED display is here, I have written some simple I2C functions to talk to it and  have just sent an initialisation sequence. It's quite a complicated driver and so requires a lot of initialisation just to get to this point. The display pattern is just random RAM data, with some other data written on top.