is it possible to get a Battery to power A LED for a LONG time?

[MrAl]

Mr Al. Thanks for your offer.

For now, I solved the immediate problem. I now just need to curt and drill and mount the switch and see if it holds up mechanically A 9Vbattery and a LED would work perfect for a quick design.

When and, if I get the Ethernet Patch panel done, I could pass that indicator upstairs to the bedrroom which is not a bad idea either. The panel is mounted, but no connections yet. Thanks for that idea. I could even do that in addition. The LED in the BR is the lowest cost.

I bought the DIN rail parts for (power supply, a few isolated contacts and a contactor that would operate off of 12 V). I would also need to cut a lowvolateg cutout for the wiring. Turning on a 120 V lamp (standard wall switch) would be PERFECT, because the lamp needs to be on to peer into the freezer.

A UPB system is inn the works too for one light.

I do have lots of sensors that need monitoring, or at least lots I could come up with. I have a wireless water alarm, but there is again no external outputs. One water alarm sits on a towel and the other has battery monitoring and is wireless and sits in the "french drain" with the receiver in the bedroom. But it doesn't help if our not home.

The refrigerator has the old fashioned locking handle, but also has a curved door so mounting will be more difficult. The door being open is more likely than it being off. There is no defrost, but I have the fridge turning off one hour a day.

I just would love to have a decent SMS alarm system that doesn't cost an arm and a leg.

Hi,

Oh so you have everything the way you want it now? That's good then. I thought maybe you wanted to do it over or something to get more accurate monitoring, but if it works, that's good and your done

 

[MrAl]

With some of the modern LED's it is possible to get about a year out of a battery. I did some tests with a super bright white LED. With a standard Alkaline 9V battery and a 4.7k resistor in series with the LED, it was real bright and consumed a little over 1 mA of current. With a 9V battery having a capacity of 550mA it would last quite a while.
Another way I have learned to adjust brightness of LED's is with a PWM supply voltage. I use a 555 timer as approximate 6% to 94% adjustable PWM generator and use that to turn on a power mosfet. With that a whole lot of LED's can be dimmed to my needs. The PWM generator has a frequency of about 100Hz.
Doing this the Led's are actually blinking but the human eye cannot see the LED's blinking, as the human eye can see blinking up to about 20Hz.

Hi,

That sounds pretty good. The reason mine gets 2 years from two AA cells is because of the very low duty cycle, but if you need yours to be lit all the time that's a different story.

If you use a 5k resistor with a 9v battery when the battery is new and you see 1ma, then the LED voltage must be around 4 volts. If that setup gives you one month of good brightness operation, then with a light duty switching regulator you would get about twice that time.
As a simpler example, if the battery was 9v and the LED 3v and the resistor gave you one month of run time, then a switcher for that system would triple the run time because the current from the battery would reduce to 1/3 of the original current, at least approximately. That's because stepping down from 9v to 3v is a ratio of 1/3 of the voltage, and with true power conversion that means (ideally) 1/3 of the current. So really the battery would only be putting out 333ua while the LED got it's full 1ma.
Would be interesting to try.

 

[Tony Stewart]

Using low current x low duty cycle and Vf on LED matching Vbat, you get, 100% efficiency such as 100mohm MOSFET
10Mohm biased Schmitt trigger astable clock and 10M biased Schmitt trigger Monostable for pulse LED.

Then duration is based on depth of discharge voltage and VAhour of battery vs load.

Eg. 3.0V Lithium cell like CR123 gives 1500 to 3000 Ah or x3 for VAh.

1ms 100mA pulse controlled by 2.50 Ohm Rs and 0.25V drop with 3W white Toshiba or good Cree LED every 1 second uses ...
0.1x 60x60 /1000 Ah = 0.36Ah thus in 1800Ah Lithium CR123 may last 5000 h
Reduce rep rate /2 and / or current to 50mA to get 10khours.

Each 10Mohm R uses average 3V/2 /10M = 150 nA and must be low leakage cap. Plastic Film is best. You can change RC to suit avail.

LED with 100mA 1ms pulse every 1 sec uses 100uA average so clock is low power.
C clock =~ 0.47uF
C monopulse = 0.47 nF

You can get CR123's on Ebay for 0.88$ but may be low Ah.


Dont forget -12V initially on Brads copy of your design may blow LEDs, Brad can you include links from now on?

 

[KeepItSimpleStupid]

Mr Al:

Door prop is more important than temperature. A simple - is it closed?, had a higher priority: e.g.www.kohls.com/product/prd-1525416/dreambaby-2-pk-refrigerator-latches.jsp?ci_mcc=ci&utm_campaign=EC BABY NON-APPAREL&utm_medium=CSE&utm_source=google&utm_product=94453392&CID=shopping15&ci_src=17588969&ci_sku=94453392

Although, I bought the temperature alarm first and because of the one hour alarm LED, decided it wasn't suitable, but I do think I cut down the potential problem significantly and I will know approximately how long the door is left open (over temperature).

I had something long ago that I have used to secure small things like a socket set top, that I'd like to find again, but can't. It was Velcro in the form of a hasp. Two hard plastic thingys attached to the case. The hook area was about 1" x 1.5" and the loop was attached much like a buckle, but flat allowing the loop stuff to pivot.

So next I'll experiment with the switch. It actually could be a decent solution without the baby latch or switch.

Then add a LED+resistor and a battery. (again simple).

Then onto either remote indication or a wall switch turned on or both.

 

[MrAl]

Hi,

You mean the switch on the door to detect if it is open?
That's pretty simple using a magnet switch, and it can detect the door open even 1/8 inch but i allow mine to open a bit more because it's mainly for the light itself that comes on so you can see inside.

The switch i use is a reed switch. The Hall switches require a bias current to keep alive, which uses battery power. This is the second reed switch now but it has been there for a long time now. The first reed switch was a 'fake' and so was not sealed or anything, and that did not work well after a few months or so. The glass ones are the best as they last a reasonably long time at low currents.

 

[Tony Stewart]

My design is like a pulsed torch, while Mr Al's is like the starter to a Bic lighter and mine will last 5000 to 10,000 hrs depending on 50 or 100mA max current initially vs =<1mA dim led on Al's

 

[MrAl]

My design is like a pulsed torch, while Mr Al's is like the starter to a Bic lighter and mine will last 5000 to 10,000 hrs depending on 50 or 100mA max current initially vs =<1mA dim led on Al's

Hi Tony,

I thought he said he wanted 1ma? That's why i suggested that. I wasnt shooting for any records

But i guess what you are saying is that 100ma pulse for 1ms at 1/1000 duty cycle produces an apparent more light than 1ma continuous?
If true i'll have to take a better look at this. I know the LED efficacy goes up as current goes down, and down as the current goes up.

In the old old old days that's all they could do, because the batteries were so bad they could only flash the light for a short time before giving the battery time to recover. That's where we got the name "flashlight".

 

[k7elp60]

Hi,

That sounds pretty good. The reason mine gets 2 years from two AA cells is because of the very low duty cycle, but if you need yours to be lit all the time that's a different story.

If you use a 5k resistor with a 9v battery when the battery is new and you see 1ma, then the LED voltage must be around 4 volts. If that setup gives you one month of good brightness operation, then with a light duty switching regulator you would get about twice that time.
As a simpler example, if the battery was 9v and the LED 3v and the resistor gave you one month of run time, then a switcher for that system would triple the run time because the current from the battery would reduce to 1/3 of the original current, at least approximately. That's because stepping down from 9v to 3v is a ratio of 1/3 of the voltage, and with true power conversion that means (ideally) 1/3 of the current. So really the battery would only be putting out 333ua while the LED got it's full 1ma.
Would be interesting to try.

Thanks MrAl for the idea, that is a great idea. I had forgotten about using the step-down switcher.

 

[Tony Stewart]

Hi Tony,

I thought he said he wanted 1ma? That's why i suggested that. I wasnt shooting for any records

But i guess what you are saying is that 100ma pulse for 1ms at 1/1000 duty cycle produces an apparent more light than 1ma continuous?
If true i'll have to take a better look at this. I know the LED efficacy goes up as current goes down, and down as the current goes up.

In the old old old days that's all they could do, because the batteries were so bad they could only flash the light for a short time before giving the battery time to recover. That's where we got the name "flashlight".

Actually efficacy goes up as ESR goes down and ESR goes down as rated power goes up. and higher efficacy LEDs , as you know will be even more efficient when running less than full,
I chose 10% of full rated current which is 1/3 of test current at 129 lpw.

This is why I chose high power running at 10% of rated current . It is the peak current that counts, but in the end 100mA at 10% of 1A is much brighter than 5 20mA LEDs unless you wanted narrow beam < 10deg, which is easier to find in 5mm but they are only 60 lpw. vs > 120lpw on new Toshiba LEDs.
Try these or any shade of white you prefer. 5000K daylight white, 4000K late afternoon white 3000K Warm White 6000K Cool white (bluish) and plan on an ALUM clad board with heat sink if using full power 100% d.f. but no need for pulse.
350mA is relatively easy to cool on 3 sqin alum but 1A needs fins or heat pipes.

Cost in 250pcs is $200 with a good design at 3Vx1A=3W is 3.75 Watts per dollar.
expect this to follow Moore's Law with 50% reduction every 3 years in these special high volume parts.

So overall, for long lasting LED on 1 battery// this is the best bang for the buck. ( or $2 for LED and battery ) Schmitt trigger not included. $0.89
https://www.digikey.com/product-detail/en/940C8W2P5K-F/338-1150-ND/809443

Astable and monostable designs are prolific on Google images. with 74HCT14 but 74LVC14 runs from 3.5 to 1.5V uses same strategy.

 

[Tony Stewart]

If you want to get 50x more life that the 5kh @100mA, then pulse at a dim 3W LED at 2~5mA for 0.1% duty cycle

 

[Mosaic]

Apparent LED brightness is linked to the pulse current...2 or 3 x peak continuous mA gives light output benefits vs energy consumption.

 

[Tony Stewart]

Yes modulation has this effect. Acuity has many variables.

 

[audioguru]

Our vision sees a light pulse duration of 30ms or longer at full brightness. Pulses less than 30ms appear to be dimmed like from a PWM dimmer circuit.

 

[Tony Stewart]

A small xenon flash at 6 million lumens only lasts 50us while cell phone flash of 100 lumens lasts 100ms.

So flashing 20mA or 65 mw @ 60 lpw or 3.9 lumens for 1ms would be ~2.4 ml-s vs 10,ooo ml-s for a cell phone flash vs 30,000 ml-s for a small xenon flash.

 

[audioguru]

I suspect that a cell phone flash uses a lot more current than only 20mA. The duration is short to reduce blur on moving objects.

 

[Tony Stewart]

20mA refers to a 5mm LED , sorry I should have included more details on the 3 examples
At 100 lpw for power AlGaN leds up to 140 lpw
and only 60 lpw on most 5mm UB AlGaN LEDs
With better power LEDs at <=3V@350mA or 1W,, worse are 3.2~3.8V.

It could also now be ~3.3W @>1A pulse @ 30ms or 10ms depending on capture time.

1/100th good for action , whereas cameras often used 1/60th not because the duration was that long,,but the pre-ionization latency was 5 to 10 ms and changed with aging, roughly, then the cap discharge ionization time of Xenon for <=50us can easily freeze the wings of a humingbird.

Smart phones now might use one shot PWM for various settings , sport or landscape

Thanks for keeping me thorough.

 

[audioguru]

20mA is the tested continuous current of an ordinary LED. The maximum peak current for a short duration is MUCH higher.
My ordinary old red 5mm LEDs are rated and tested at 20mA. 40mA is their maximum allowed continuous current when the ambient is 25 degrees C. The maximum allowed pulsed current is 200mA at 1kHz, 10% duty cycle.

 

[Tony Stewart]

how many milli-lumens is that

 

[MrAl]

Hi,

Didnt you mean to say microlumens? (har har)

Did they make LEDs back then that had even 100mcd ratings?
If so, i'd guess about 150 mLumens at 20ma, and 151 mLumens at 200ma
Ok just kidding about the 151, maybe 0.5 Lumens.

1:50 am <now putting the beer down>
1:51 am <ok it's been down long enough>

 

[Tony Stewart]

Hi,

Didnt you mean to say microlumens? (har har)

Did they make LEDs back then that had even 100mcd ratings?
If so, i'd guess about 150 mLumens at 20ma, and 151 mLumens at 200ma
Ok just kidding about the 151, maybe 0.5 Lumens.

1:50 am <now putting the beer down>
1:51 am <ok it's been down long enough>

Since you are being so generous, ...passes microbrew...
20mA at 3.3V is roughly 65mW max rated for thermal insulation of epoxy is high, limiting power dissipation and efficacy drops ~60% when driven at max current rated by gold whisker wirebond max.
thus 60 lpw*65mw = 3.9 lumens is possible at nominal in modern Ultrabrite 5mm LEDs. and 1% of this at best in 20 year old GaAs technology as I recall.

Most 1.5mm chips used are only 60 lumens per watt (lpw), Some 2.2mm chips are more in 5mm case ( rare)