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Add a low power indicator LED

jack0987

Member
I have some small battery powered Arduino sensors in plastic cases about the house.

My thinking is I would like to drill a small hole and put an led behind it to add a small indicator led to each so when I look up at them and the led is lit I know the battery is not dead yet.

The Arduino runs on low power and only wakes up on an interrupt. With a T5 led ran for about 10 days. The Arduino has an led and so far it has run 90 days.

Perhaps size matters.

Please suggest some ideas. low cost is best.

Edit: Changed thread Title
 
Last edited:

jack0987

Member
Far more important than the test current spec, is the luminosity at that current.
The part you link to will put out ~64 mcd at 2 mA.

Here is a part that puts out ~1600 mcd at that same 2 mA.
https://www.digikey.com/en/products/detail/kingbright/WP7113LVBC-D/5177420

You can either run it at 2 mA, or reduce the current (and power) significantly, and still get a usable level of light.

Thanks. I did spot that 5mm one now, but there is a 3mm version which I would prefer. High light level is not as important to me. As long as I can see it is all that matters.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
High light level is not as important to me.

High light output for a given current means LESS current to get the SAME light.

I have some ultra-bright LEDs that are as bright as basic LEDs such as used for "power on" indicators with just a few microamps current, rather than milliamps.

[I was going to suggest them at the start of this thread, but the exact type I have i no longer available).
 

Papabravo

Well-Known Member
Thanks. I did spot that 5mm one now, but there is a 3mm version which I would prefer. High light level is not as important to me. As long as I can see it is all that matters.
Yes, but the higher light level for a given current means you can reduce the duty cycle to almost nothing and get an acceptable result that won't drain your battery. You need to start playing 3-D Chess.
 

jack0987

Member
High light output for a given current means LESS current to get the SAME light.

I have some ultra-bright LEDs that are as bright as basic LEDs such as used for "power on" indicators with just a few microamps current, rather than milliamps.

[I was going to suggest them at the start of this thread, but the exact type I have i no longer available).

I am wondering if the type mounted on circuit boards may take much less power.
Here is a not so good picture of what I mean.
BoardLED.jpg

Being so small, they will be a challenge for me to work with.
What do you think?
 

jack0987

Member
Yes, but the higher light level for a given current means you can reduce the duty cycle to almost nothing and get an acceptable result that won't drain your battery. You need to start playing 3-D Chess.

Playing 3-D chess?

I did get in some 3mm dome leds and they say 2mA. They are surprisingly quite bright. Much, much brighter than I would like.

How does one reduce the duty cycle?
 
Playing 3-D chess?

I did get in some 3mm dome leds and they say 2mA. They are surprisingly quite bright. Much, much brighter than I would like.

How does one reduce the duty cycle?

Create your duty cycle by coding it to turn on the LED for X milliseconds and off for Y milliseconds. The X being your duty cycle. X+Y=period of signal. And just loop that whole sequence for however long you need. Adjust X and Y until you hit your sweet spot.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I just drilled a much smaller hole for it to shine through.
Question: Would a higher value resistor reduce it's power consumption?
Yes, of course, simply apply ohms law - however, less current means less brightness - much of this thread has been about increasing the resistor to reduce current (and brightness).
 

jack0987

Member
How can you be 'uncertain'?- an LED on all the time uses ten times the power of one that's only on 10% of the time - so will only last 1/10th of the time. You don't 'continuously power up the processor', it's in sleep almost all the time, which presumably it already is anyway?.

What don't you understand about that?.

I feel certain, in the end, I will be doing as you suggested once I take the time to study it. LOL
 

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