Ring Clock Idea Help

Hello! I am an engineering student interested in doing some projects for fun and to learn a bunch of new things. I have a few ideas for projects to do, however nothing is very usable except for this one.

I would like to make my own "smart ring" that you wear on your finger that just 'simply' tells the time. I only want the time because I think that would be useful (and perhaps possible). However, I am an aerospace engineering student, so my knowledge for electronics is limited and that's where I need concept help.

There are very small digital displays that may work for this project, but it may be too difficult. I am also thinking about showing the time with lights to make it simpler (24 light total, 12 for hours 12 for 5 minute periods or 12 lights total. I think 12 lights would be the best starting point to figure things out initially). Does anyone know if this would be possible to achieve? I am thinking it can be done if I used a small bluetooth chip that told the lights when to turn on or there might be a very easy way to make a clock with small electronics that I'm just unaware of and unable to find through the internet.

I could go on about my thought process, but I want to keep this first post somewhat short.

Thank you for any responses and I could go into more detail on what I have in mind for the lights if my explanation was confusing. If this isn't possible but you have a project idea that would help me learn this type of stuff, let me know, I always love learning new things and it's the reason for this idea in the first place.

The 24 lights (LEDs ?) would need to be visible at the same time in order for the time to be read. Is that practical ?

The ring would need to be powered. How do you propose to power such a small device

The time would need to be set and/or adjusted How do you propose to do that ?

If you are going to sue a Bluetooth device, perhaps a smartphone, to control the ring then why do you need the ring to show the time in the first place ?

my thought would be to make a bluetooth ring…
Feed the data to a shift register & leds… with an app running on your phone.
That reduces the complexity, size and power consumption of the actual ring.
Whenever the phone & ring are in range, the app sends whatever you want to the ring.
LEDs may be good, but typically will use more power than something else.

A chip like MAX7219 could help??

Of course, if you go to a tiny processor, you could multiplex the LEDs to reduce the continuous current draw. Maybe even sleep the cpu for 90% of the operating time.

All food for thought.

The primary reason for this project is to learn about arduino. It's also just as a fun and challenging project to occupy my time.
I completely agree that 24 LEDs wouldn't work whatsoever, and even doing something like 12 would be difficult. I could perhaps just make this as a watch instead which would allow for more room and be easier since mostly all of this is new to me.

So, if I did it as a watch, i know batteries wouldn't be an issue since there are many available small batteries that could fit in that size. The main issue is that I have no clue about is how to send a specific bluetooth signal to a receiver to then light up an array of 12 LEDs.
Also, thank you for your very practical and straight forward questions about the practicality of the project idea

Thank you for the feedback and help!
This is primarily the idea I had in mind, however I am not sure how to create that custom bluetooth signal to show a time through an app on my phone, but I think I might be able to figure out how to do that if I spend a bunch of time googling and testing. (I have no idea what parts are needed to receive the bluetooth signal and if it can just tell a light to turn on or off so I don't need any processing in the ring)
Since I am also new to many of these things, would this tiny processor with multiplexing LEDs be used in conjunction with the bluetooth signal? If so, i'd probably need a board to go with it which would make space a large problem or maybe I just have to manually wire all the components.

how large (physically) is this going to be?

This is something I still need to figure out based on the minimum hardware it would require. For the general concept however, it is probably best to figure out how to make this as a watch, so that physical space isn't an issue, then, later on, reflect to see if the size could be shrunk down significantly. I have a lot to learn about all of this stuff, so the size requirements are very loose.

with enough money you can shrink it - see for example what they pack in the LILYGO TTGO T-Watch


Start with a giant ring of real LEDs. Or smart LEDs. Try both.

Use a RTC module and play with displaying time variously.

Work on the code and the ideas you have around using have around blue tooth, which may or not be a way to go.

Rinse, shrink and repeat.

What programming experience and knowledge is already, and how much are you will you need to learn?

Google "ouraring" for inspiration…


I know C, Java, Python and MATLAB very well, and a little bit of a few others. I'm very comfortable with learning a new language and learning a lot of new things.

As I searched through things online, I found stuff with RTC, but I need to look more into them to figure out how to give the RTC power and use it to light LEDs in the way I want. I feel like that would require some processing however. If Its not clear enough for what I want to do with the LEDs, (updated) I'm thinking using 10 LEDs, where 5 are used for hours and 5 are used for every 10 minutes. (I think that's how it would work out, not 100% sure though, its very late for me) Then 0:00-5:50 would be displayed first, then 6:00-11:50 second and so on through the whole day.

Thanks for the response and I'll do some more research on using an RTC module as I think it will be the easiest, then I can later on figure out bluetooth signals

Your development prototype won’t be small, it will be built on breadboard or protoboard to prove the electronics, test the power budget, and develop any host app.

Once you have the idea working, then comes the hard part - to miniaturise it to a ring or bangle size.

Once all the elements are in place, you can tweak the host software any way you want, but the initial goal is to design & test your display module to get what you want…

If you can later miniaturise all your control circuitry as well - great, but Insuspect that’s a bit ambitious for rev 1.

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