Lighted jewelry help

[Cosmicray]

Would there be a way to make a small led light glow (even dim) constantly for six months to a year (or longer) using thin, and lightweight, batteries? I'm thinking that cell phone batteries will be small and light weight enough but not sure if it has enough stamina. The smallest led bulb I can find is 3mm. Is there anything smaller or more efficient? What would be the best minimalist setup?

 

[ronsimpson]

What color of light? White, red, green......
Some batteries can not hold a charge for a year with out a load. So there is that problem.

Here is a curve on the first battery I picked.
At 10mA of LED current, we have 800 hours of life.
At 3mA, we have 4000 hours or about 1/2 year.
At 1.5mA, the batter should last about the 1 year you want.

LT-5920 8.5Ah, 3.6V

So the real questions are:
Is this battery too large?
How much current do you need? (get a LED and try it)

There are other things to think about but this is a good starting point.
---------edited------------
Can we turn off the LED at night and save power?
Rechargeable battery?

 

[djsfantasi]

I don't know about making these LEDs light for that long, but there are smaller LEDs, in SMD format. Search for "1.6mmx1.6mm SMD LEDs". That's a quarter of the size of your 3mm LED. They are also RGB LEDs, so you can get any color that you want, with appropriate resistors. If you were to searcg longer, you may be able to find small SMD LEDs of a single color. I just

How many LEDs are you trying to light? Just one? They use 20mA for each color. To light it for a year, you would need a battery that could provide 175,000 mAH. That is 365 days times 24 hours/day times 20 mA. Unlikely to find a battery with that much power in a small size, small enough for jewelry. Of course that is running the LED at maximum power. If the LED operates as low as 5 mA, you would only need a 43,800 mAH battery

 

[Cosmicray]

What color of light? White, red, green......
Some batteries can not hold a charge for a year with out a load. So there is that problem.

Here is a curve on the first battery I picked.
At 10mA of LED current, we have 800 hours of life.
At 3mA, we have 4000 hours or about 1/2 year.
At 1.5mA, the batter should last about the 1 year you want.
View attachment 98874
LT-5920 8.5Ah, 3.6V

So the real questions are:
Is this battery too large?
How much current do you need? (get a LED and try it)

There are other things to think about but this is a good starting point.
---------edited------------
Can we turn off the LED at night and save power?
Rechargeable battery?

Thank you for your answer, Ron.

I do envision using all colors and I'm aware of white being the biggest energy drain.

If that is a size C battery then it will be too big. I envision something much smaller (like a AAA battery) or flatter (like a cell phone battery) but perhaps a plural of them in a parallel to increase the stamina.

I tested a small watch battery on a 5mm LED and it drained it in 50 hours. I was hoping to get smaller lights and bigger batteries to make lights glow for much longer.

I would rather have the ability to turn the lights off during the day or in the light and make them glow at night and in the dark but I wouldn't know how.

I don't think rechargeable batteries will be best for this application because of the increase in capacity and have less of a discharge rate. Am I right about this?

 

[Cosmicray]

I don't know about making these LEDs light for that long, but there are smaller LEDs, in SMD format. Search for "1.6mmx1.6mm SMD LEDs". That's a quarter of the size of your 3mm LED. They are also RGB LEDs, so you can get any color that you want, with appropriate resistors. If you were to searcg longer, you may be able to find small SMD LEDs of a single color. I just

How many LEDs are you trying to light? Just one? They use 20mA for each color. To light it for a year, you would need a battery that could provide 175,000 mAH. That is 365 days times 24 hours/day times 20 mA. Unlikely to find a battery with that much power in a small size, small enough for jewelry. Of course that is running the LED at maximum power. If the LED operates as low as 5 mA, you would only need a 43,800 mAH battery

Wow! It will definitely be a challenge to overcome. I might toy with using flashing or pulsing lights that will be in the off position for most of the time to lengthen the life. I would be happy to get six months out of a battery. Think that is feasable?

 

[cowboybob]

Welcome to ETO, Cosmicray!

Can't fight Ohm's Law.

... I might toy with using flashing or pulsing lights that will be in the off position for most of the time to lengthen the life. I would be happy to get six months out of a battery.....

Even a pulsed LED is drawing power in between pulses. Not much, to be sure, but a draw. Keep in mind that an LED will emit light at considerably lower currents, just not a bright (obviously).

Here's an extremely low current LED (1mA at 1.6Vf, red): https://www.digikey.com/product-detail/en/broadcom-limited/HLMP-K150/516-1311-ND/637575, Check the datasheet (on that page - a PDF) for more info. In dark environs this might work for you.

 

[djsfantasi]

And in addition, you will have to account for the current draw of the circuit you come up with to flash the LEDs.

You didn't answer... Are you lighting one LED or more?

Also, how bright do you expect the light to be? Brighter usually implies more current.

 

[Cosmicray]

Welcome to ETO, Cosmicray!

Can't fight Ohm's Law.

Even a pulsed LED is drawing power in between pulses. Not much, to be sure, but a draw. Keep in mind that an LED will emit light at considerably lower currents, just not a bright (obviously).

Here's an extremely low current LED (1mA at 1.6Vf, red): https://www.digikey.com/product-detail/en/broadcom-limited/HLMP-K150/516-1311-ND/637575, Check the datasheet (on that page - a PDF) for more info. In dark environs this might work for you.

Thank you for your help!

1mA could really help me achieve what I envision. I'm assuming that you could feed it .5mA and it would almost double the life of the battery but cut the light output in half.

 

[Cosmicray]

And in addition, you will have to account for the current draw of the circuit you come up with to flash the LEDs.

You didn't answer... Are you lighting one LED or more?

Also, how bright do you expect the light to be? Brighter usually implies more current.

For simplicity's sake, we can model a single led/battery circuit and I can scale up from there. I've even thought about using fiber optics to feed different parts of the jewelry using a single bulb.

I would like it to be bright enough to be seen inside of a low lit room.

 

[cowboybob]

... 1mA could really help me achieve what I envision. I'm assuming that you could feed it .5mA and it would almost double the life of the battery but cut the light output in half. ...

No.

A datasheet (see link above) is your friend:

They, generally, answer most questions concerning devices' capabilities/limits.

 

[Cosmicray]

No.

A datasheet (see link above) is your friend:
View attachment 98892
They, generally, answer most questions concerning devices' capabilities/limits.

Gotcha. I must have missed that part. Thank you.

 

[ronsimpson]

to feed different parts of the jewelry using a single bulb.
I would like it to be bright enough to be seen inside of a low lit room.

If you divide the light between several places the brightness goes down!
Fiber is not 100% efficient so there is loss there.

This sounds like a indoors project. Could you use a solar panel to recharge the battery? (Like a side walk lamp) Inside there is not much power from indoor light but it will recharge some.

If you use fiber then maybe a large battery could be put in a good place.

 

[Cosmicray]

If you divide the light between several places the brightness goes down!
Fiber is not 100% efficient so there is loss there.

This sounds like a indoors project. Could you use a solar panel to recharge the battery? (Like a side walk lamp) Inside there is not much power from indoor light but it will recharge some.

If you use fiber then maybe a large battery could be put in a good place.

The photovoltaic is a great idea and one that I have considered but I don't think it would be feasable for this application. I've also considered a kinetic energy collector since it will be worn but it will be an enormous challenge to scale down the components needed to turn it into electricity.

 

[ronsimpson]

I now see what you are doing.
Here is a picture of something I was involved in some years ago. This thing is made by the millions. About any single color or there is one that randomly goes through 64 different colors.
On off switch by touching it.
Size=2016 battery.
Some have different modes, on, off, blink, fast blink,
Time= depends on color but about 40 hours. If we reduce the brightness that could go much longer. It is designed for full brightness on the LED.

This is the old version.
I have made much smaller but the "on/off/blink" goes away.
The short battery life is OK because you shut it off when not in use.
I think I can reduce the light (current) by 5:1 or 10:1 for any single color but I think the random color version might no have that option.

 

[Cosmicray]

What color of light? White, red, green......
Some batteries can not hold a charge for a year with out a load. So there is that problem.

Here is a curve on the first battery I picked.
At 10mA of LED current, we have 800 hours of life.
At 3mA, we have 4000 hours or about 1/2 year.
At 1.5mA, the batter should last about the 1 year you want.
View attachment 98874
LT-5920 8.5Ah, 3.6V

So the real questions are:
Is this battery too large?
How much current do you need? (get a LED and try it)

There are other things to think about but this is a good starting point.
---------edited------------
Can we turn off the LED at night and save power?
Rechargeable battery?

Ron, in your model you noted that an 8.5 Ah battery could power a 1.5mA LED for almost a year. I have found a battery that claims 10Ah https://www.tenergy.com/30123 that may be perfect for my application and cowboybob pointed out an LED that has a minimum current of 1mA https://www.digikey.com/product-detail/en/broadcom-limited/HLMP-K150/516-1311-ND/637575 . Would this setup light the bulb for well over a year?

 

[Cosmicray]

I now see what you are doing.
Here is a picture of something I was involved in some years ago. This thing is made by the millions. About any single color or there is one that randomly goes through 64 different colors.
On off switch by touching it.
Size=2016 battery.
Some have different modes, on, off, blink, fast blink,
Time= depends on color but about 40 hours. If we reduce the brightness that could go much longer. It is designed for full brightness on the LED.
View attachment 98896
This is the old version.
I have made much smaller but the "on/off/blink" goes away.
The short battery life is OK because you shut it off when not in use.
I think I can reduce the light (current) by 5:1 or 10:1 for any single color but I think the random color version might no have that option.

I have seen some 3mm LEDs on the internet that flash. I like the small size and the flashing could potentially save energy and extend battery life without having to wire additional components.

 

[djsfantasi]

If you have found flashing LEDs, what does their datasheet say about their current draw?

Using the 1.5 LEDs draw and a 10AH battery will last about 9 months.

You may be able to calculate these observations yourself. There are 8760 hours in a year. Multiply that by your anticipated current draw (in mA), and the resulting number is the mAH rating of a battery to operate your circuit for a year.

Or it's possible to calculate the estimated time of operation, given the battery's mAH rating and the current draw. I'm on my phone? So cannot derive it now, but it can be done.

 

[djsfantasi]

This just in. I found some 3mm flashing LEDs online. They draw 20ma. With a 10AH battery, they would last about 20 days. Take the batteries rating of 10000mAH, and divide it by 20mA, giving you 500 hours of (perfect) life. Divide again by 24 hours in a day, and get 20.8 days.

Note I specified "perfect". Batteries cannot be discharged totally, the the actual life is smaller.

 

[ronsimpson]

The flashing LEDs usually don't have a good way to reduce the current.

Please post the part number or data sheet.

 

[audioguru]

I have some excellent old Hewlett Packard LEDs then they changed the name to Agilent that were pretty good but now they changed the name again to Avago who is half Chinese and half American.
The brightness numbers on the "efficient" LED at 1mA are the lowest I have ever seen. Maybe it must be in a pitch black room to be seen.