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xmas present: blinking ring

Sophia Lorenzo

Nov 17, 2016
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Hello.
I like to present a gift to my little niece. She is young and loves anything that has a colourful light and blinks. I like to make a ring with a switch that blinks for a couple of minutes when pressed.

I am not very experienced and dont know how to start off with this project. Anybody who can give a hint how to realize a blinking ring?

Thank you!
Sophia
 

Harald Kapp

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Welcome to EP, Sophia.

How 'not very experienced' are you?
Would you be comfortable to program a small microcontroller? Or would you prefer (and be able) to build a discrete circuit using e.g. a pair of 555 timers (or 556 dual timer) plus a handful of discrete components (ressitors, capacitors and such)?
Do you know how to build a circuit on a prototype PCB (e.g. veroboard)?

The most simple discrete circuit I can envision is a 555 based monostable multivibrator plus a self-blinking LED.

However you tackle this, it is going to be a rather bulky project (bulky with respect to the purpose). You're probably better off buing an off the shelf ring like one of these.
 

Sophia Lorenzo

Nov 17, 2016
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Hey Harald.
Thanks for your reply!
I have not done anything beyond swapping a fuse or testing a relay. I am a fast learner, interested and have skills, though. Id really like to do the ring myself.
I assume the microcontroller seems the best way to go as it will need less components and the ring will be smaller. What is the smallest microcontroller I can buy and how can it be programmed? What is the smallest battery and switch you can think off that would work?

Thanks
Sophia
 

Harald Kapp

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I am a fast learner, interested and have skills, though. Id really like to do the ring myself.
O.k. Note that you will have a steep learning curve. I definitely don't want to disencourage you.
You'll have to:
  • understand how a microcontroller works
  • learn how to write, test and debug a program for a microcontroller
  • learn how to program a microcontroller (downlod the code from the PC to the controller)
A very small microcontroller is e.g. an Attiny85. A suitable battery would be e.g. a CR2032.
Note that for programming the microcontroller you need
This website or this website or this website might get you started. You may want to get your hands on a starter kit.
 

KJ6EAD

Aug 13, 2011
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Something like a neopixel ring would be nice but it's not very child friendly and requires significant power.

1643-01.jpg

https://www.adafruit.com/products/1...4tX0U-bNbXSpeXL4L8m9dJAskGJm5oB7kEaAtyR8P8HAQ
 

Sophia Lorenzo

Nov 17, 2016
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Thank you Harald! What kind of switch would work? It should be small. After i have the electric parts working, i will make a transparent silicone case as the ring itself. I plan that you can switch it on by pressing the ring at a certain area.

Yeah KJ, the neopixel looks nice, but the battery outside makes it difficult to wear around the finger. Thanks though.
 

Sophia Lorenzo

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The attiny85 is shipped from the manufacturer in the US and I had to request a single unit to be shipped. They havent replied whether theyll do it as they seem to supply companies with bigger demands rather than individuals. So, I was looking on amazon UK but did not find the small attiny85-20mu. Do you know a place in the UK or Europe to order it?

Thank you
Sophia
 

Harald Kapp

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Is that the one?
Nay, go to companies like RS, Mouser, Farnell, Adafruit, Digispark etc.

You may want to have a look at the trinket. It will require a bit higher voltage than a CR2032 can supply, but small LiPo rechargeable batteries are easy to come by. However, that leaves you with the additional issue of providing a means to charge the LiPo...
 

KJ6EAD

Aug 13, 2011
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The required form factor, a child-sized ring for a finger makes any DIY option extremely difficult. How about a bracelet?
 

BobK

Jan 5, 2010
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How large do you expect this to be? Can you give us a rough drawing with dimensions?

The microcontroller that you linked to would require a reflow oven to solder. Not something a beginner would be using.

Bob
 

Herschel Peeler

Feb 21, 2016
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Hey Harald.
Thanks for your reply!
I have not done anything beyond swapping a fuse or testing a relay. I am a fast learner, interested and have skills, though. Id really like to do the ring myself.
I assume the microcontroller seems the best way to go as it will need less components and the ring will be smaller. What is the smallest microcontroller I can buy and how can it be programmed? What is the smallest battery and switch you can think off that would work?

Thanks
Sophia

Electronic Goldmine sells a lot of blinking LEDs. Among then are some that blink multiple colors. A ring would be a problem size wise. Not much room for a battery in a kid size ring. Maybe a necklace. Can you cast metal?
Make the design you want out of wax. Put that in Plaster of Paris. Pour in molten metal of your choice.
Microcontroller? To blink an LED? Overkill.
555? Why not just "blinks while holding a switch"?

7555 schematic is attached and a picture of the LED.
 

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Sophia Lorenzo

Nov 17, 2016
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Thanks guys!
I will play around a bit with the different ideas. I assumed that the micro controller is more to make it stop blinking after a couple of minutes so that my niece does not have to remember to switch it off everytime and the battery will last longer that way. Does that need a microcontroller?
The design can be in the shape of a cylinder (1x1x3cm) which is attached to a ring to put on the finger.
Thanks for the web addresses, Harald!

Thank you
Sophia
 

BobK

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That size is definitely doable. You would probably want to use 2 or 3 button batteries. LR44 is a popular size that is 1.1 cm in diameter and used in many small LED devices from China. I am sure you could find another one that is a little less than 1cm if necessary.

Bob
 

Sophia Lorenzo

Nov 17, 2016
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Great! Thank you, Bob.

Another thing i ponder about: the LED should stop blinking after a couple of minutes. Is the 7555 suitable for that purpose. I attached the design from Herschel Peeler, how kindly posted it to me!
 

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BobK

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There are small tact switches (pushbuttons) that should be suitable.

Bob
 
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