Add a low power indicator LED

[jack0987]

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

 

[Nigel Goodwin]

I would have used a simple RED 3mm LED.

And you don't mind driving 300 miles every week to replace the batteries?

 

[danadak]

When you measure Arduino current lift the power pin on the Arduino as the
board uses current for the RS232 interface and other stuff. If you want its real
current measur.re it there.

Depends on the board/proto setup you are working on.. Note you want
the LED driven by the Arduino so its power is supplied thru Arduino supply pin.

Or make sure where you decide to measure current the LED is supplied with
power.

Note a DSO also makes it easy to measure total power consumed over time
with its math functions.


Regards, Dana

 

[jack0987]

https://www.mouser.com/c/optoelectronics/led-emitters/?mounting%20style=SMD%2FSMT&product=Blue%20LEDs&product%20type=LED%20-%20Standard&instock=y

Thanks.

 

[jack0987]

And you don't mind driving 300 miles every week to repalce the batteries?

I will, in the end here, do some testing. LOL

I do have one running at the moment as sort of a test. About 110 days so far with a 2000 mAh 3.3-volt lithium battery.

 

[jack0987]

View attachment 138102

Regards, Dana.

Readability may be the key to choosing a color for an indicator. Please note how each color stands out on the black and white backgrounds.

 

[Nigel Goodwin]

Readability may be the key to choosing a color for an indicator. Please note how each color stands out on the black and white backgrounds.

View attachment 138200

A flashing indicator, of whatever colour, is FAR more catching than a static one - if not down right annoying

 

[jack0987]

I would have used a simple RED 3mm LED.

I think that is just what I am going to do.

 

[jack0987]

https://www.mouser.com/c/optoelectronics/led-emitters/?mounting%20style=SMD%2FSMT&product=Blue%20LEDs&product%20type=LED%20-%20Standard&instock=y

Thanks. For low power, should I choose one with the lowest forward voltage?

 

[jack0987]

A flashing indicator, of whatever colour, is FAR more catching than a static one - if not down right annoying

Blink rate and duration may also be taken into consideration.

 

[Nigel Goodwin]

Blink rate and duration may also be taken into consideration.

As I suggested testing in post #20 - I suspect you will be surprised how short a flash you can get away with. Depending exactly what your application is you may be able to add extra functionality by flashing at different speeds or intervals, I use this on a device we manufacture to give an indiction of battery life - slow flashing when fully charged, getting faster as it discharges.

I monitored the battery charging and discharging voltages and currents, and send them out the serial port to a PC and wrote them to a comma delimited file. Then I used EXCEL to generate graphs based on the charge and discharge characteristics (you only need voltage for discharge), then simply grabbed values at 100%, 90% etc. down to 10%. Once it gets to the 0% point everything is turned off.

 

[jack0987]

Our discussion has been interesting, but I do not feel that I am any farther ahead than when I started.

I remain uncertain that continuously powering up the processor for a blink will save battery power instead of running a very low power LED all the time.

My Arduino processor has a built in power LED. So far, my test with it on all the time has run now for nearly 120 days. I felt that making up an indicator with a tiny one like that might be the way to go for now and I'll look into processor blinking later.

So, I took one of the Arduino LEDs off a non-working board but I am finding very hard (near impossible) to work with because it is so small.

Am I right in assuming that the Arduino's LED consumes less power?
I do not know what to look for in the hundreds of types available.

Can you suggest a blue one of similar specs that I can work with?

 

[Nigel Goodwin]

Our discussion has been interesting, but I do not feel that I am any farther ahead than when I started.

I remain uncertain that continuously powering up the processor for a blink will save battery power instead of running a very low power LED all the time.

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?.

 

[Papabravo]

Thanks. For low power, should I choose one with the lowest forward voltage?

Nope! You want the one with the lowest current that will produce an acceptable level of illumination. Since the LED will have a persistence when the current is removed you want to find a duty cycle that will give the visible illumination required with the minimum possible current.

 

[jack0987]

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?.

Thanks. I know, I know, I am hard at times. LOL

Anyway, for the time being, I Found this:

https://www.digikey.com/en/products/detail/sunled/XZCFBB53W-8VF/10449774

Specs say 2mA.

3mm ones I was going to use say 20 mA.

I think I'm getting the hang of it and have been looking in the wrong places.
The sensors are about the house and I can easily modify them later.

 

[jack0987]

Nope! You want the one with the lowest current that will produce an acceptable level of illumination. Since the LED will have a persistence when the current is removed you want to find a duty cycle that will give the visible illumination required with the minimum possible current.

Thanks. I found this:

https://www.digikey.com/en/products/detail/sunled/XZCFBB53W-8VF/10449774

Thing is, can I work with it?

 

[Papabravo]

Thanks. I found this:

https://www.digikey.com/en/products/detail/sunled/XZCFBB53W-8VF/10449774

Thing is, can I work with it?

You should be able to find a combination of current and duty cycle that works for you.

 

[danadak]

Considerations for sleep mode :

Understanding MCU sleep modes and energy savings - Embedded.com

Whether they’re used in smart meters, wireless sensor nodes, or mobile health monitoring products, microcontrollers (MCUs) are at the heart of almost

www.embedded.com

Here is a representative processor and results :

https://www.infineon.com/dgdl/Infineon-AN86233_PSoC_4_and_PSoC_Analog_Coprocessor_LowPower_Modes_and_Power_Reduction_Techniques-ApplicationNotes-v09_00-EN.pdf?fileId=8ac78c8c7cdc391c017d0737cdb15b82

Regards, Dana.

 

[ChrisP58]

Thanks. I know, I know, I am hard at times. LOL

Anyway, for the time being, I Found this:

https://www.digikey.com/en/products/detail/sunled/XZCFBB53W-8VF/10449774

Specs say 2mA.

3mm ones I was going to use say 20 mA.

I think I'm getting the hang of it and have been looking in the wrong places.
The sensors are about the house and I can easily modify them later.

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.

 

[Papabravo]

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.

What's the cost differential?

 

[ChrisP58]

The 1600 mcd part is less expensive.