Diode LED power consumption

[BenStark]

I intend to build some dummy alarm controls.

 

So I will have a small box with a single red diode LED powered by a battery.

 

I can find that an average 1.5V diode LED consumes about 20mA, and that an AA battery on average is about 3000mAh.

 

Does that mean that I would have to change the battery every 150 hours, or are my calculations wrong?

 

Any other suggestions how to build this and make it last long are welcome.

[Crossy]

You probably won't be able to light a red LED on a straight 1.5V battery, and a naked LED needs some form of current limiter (a resistor) anyway.

 

20mA will give you a very bright LED!

 

There are numerous DIY circuits that will flash a LED on a 1.5V cell and will potentially run for a number of years!! These circuits are often referred to as a "Joule thief" because they will keep on flashing when the cell would normally be considered dead.

 

You can probably find a ready built 1.5V LED flasher on AliExpress or Lazada.

 

EDIT Something like this 

https://bluecharmsolutions.com/product/1-5v-led-flasher-circuit-board-assembly-with-red-led-astable-multivibrator-blinking-led/

[BenStark]

1 hour ago, Crossy said:

You probably won't be able to light a red LED on a straight 1.5V battery, and a naked LED needs some form of current limiter (a resistor) anyway.

 

20mA will give you a very bright LED!

 

There are numerous DIY circuits that will flash a LED on a 1.5V cell and will potentially run for a number of years!! These circuits are often referred to as a "Joule thief" because they will keep on flashing when the cell would normally be considered dead.

 

You can probably find a ready built 1.5V LED flasher on AliExpress or Lazada.

 

EDIT Something like this 

https://bluecharmsolutions.com/product/1-5v-led-flasher-circuit-board-assembly-with-red-led-astable-multivibrator-blinking-led/

 

 

Thanks I'm looking it up now.

 

Any suggestion on which type of battery would last the longest?

[BenStark]

This is ll I would need?

 

https://www.lazada.co.th/products/1-set-3-pcs-yx8018-8018-to-94-joule-thief-dc-dc-converter-booster-ic-125v-yx8018-8018-to-94-solar-light-joule-thief-dc-dc-converter-booster-ic-125v-i3978698348-s15403709367.html?

[OneMoreFarang]

2 hours ago, BenStark said:

I can find that an average 1.5V diode LED consumes about 20mA

Depending on the color a typical LED has a voltage drop of 2.0V up to 3.5V.

Like Crossy wrote, 20mA is bright. 10mA or less should do the job (depending on where the LED is like bright sunlight or a dark room).

If you want to save space, then use a lithium coin battery.

If you have lots of space, consider a 9V battery.

 

 

 

[Muhendis]

2 hours ago, Crossy said:

You probably won't be able to light a red LED on a straight 1.5V battery, and a naked LED needs some form of current limiter (a resistor) anyway.

 

20mA will give you a very bright LED!

 

There are numerous DIY circuits that will flash a LED on a 1.5V cell and will potentially run for a number of years!! These circuits are often referred to as a "Joule thief" because they will keep on flashing when the cell would normally be considered dead.

 

You can probably find a ready built 1.5V LED flasher on AliExpress or Lazada.

 

EDIT Something like this 

https://bluecharmsolutions.com/product/1-5v-led-flasher-circuit-board-assembly-with-red-led-astable-multivibrator-blinking-led/

Add to that a bit of PWM (Pulse Width Modulation) at say 1kHz, and the LED will look as though it's on full time but will only use power in accordance with the mark space ration of the PWM.

In other words if the ratio is 9:1 (that's 9 "off" and 1 "on") then the LED will look like it's on but only use 10% of your 20mA power.

All is explained here but you need a basic understanding of electronics to ......well.........understand it.

 

https://www.instructables.com/PWM-pulse-Width-Modulation-Power-LED-Dimmer/

[Crossy]

@BenStark Do you want your LED on constantly, or to blink in an "alarm set" manner??

 

[GammaGlobulin]

1 hour ago, BenStark said:

 

 

Thanks I'm looking it up now.

 

Any suggestion on which type of battery would last the longest?

 

There are nuclear batteries, based on GAMMA Decay, ie GAMMAvoltaics, that can last thousands of years.

Unfortunately, these GAMMAvoltaic devices have outputs measured in microwatts, and, unless you have very many of them, probably will not supply enough to power an LED.

Still, ongoing research may be able to increase power output, somewhat.

I am looking forward to the improvement of GAMMAvoltaic devices which will improve the life of batteries.

 

 

[BenStark]

48 minutes ago, Crossy said:

@BenStark Do you want your LED on constantly, or to blink in an "alarm set" manner??

 

 

Always on would be a plus, obviously will have to change battery more often, so blinking would be good enough.

Most important is that the battery lasts as long as possible

 

I should add, they will be used outside, so the main purpose is at night, and as such they don't have to be too bright either to be detected

 

 

[Muhendis]

1 hour ago, GammaGlobulin said:

I am looking forward to the improvement of GAMMAvoltaic devices which will improve the life of batteries.

Yeah.

We all are.

[GammaGlobulin]

2 hours ago, Muhendis said:

Yeah.

We all are.

 

I love dry humor, Sir!

 

[Fruit Trader]

Simple solution LM3909 IC probably get 2 years operation from a D cell.

 

LM3909 Datasheet 2.pdf

 

 

 

 

 

 

 

[BenStark]

Actually in the past there were some similar devices attached, but they got their feed from the alarm system which is now dysfunctional.

 

I opened such a box and other than the diode, a few resistors and a bunch of wires, there is a LM555CN IC and these 2 items.

Will this stuff be useful for my little project. To be clear, I'm not gonna do this myself, but give it to my local tv repair guy, who isn't the brightest spark.

 

[bluejets]

14 hours ago, OneMoreFarang said:

Depending on the color a typical LED has a voltage drop of 2.0V up to 3.5V.

Red LED is typically 1.7v with yellow, amber , green and blue going up to around 3.2-3.4v.

Running the LED on even 5mA will , in many instances, be sufficient.

PWM the LED will allow even longer battery life but then you need to power the pwm driver circuit.

Reduced current would be your best approach.

Note that the 9V battery will be bugger all capacity and should always be kept for it's purpose, meters or smoke alarms, that's it.

[bluejets]

17 hours ago, BenStark said:

and that an AA battery on average is about 3000mAh.

I seriously doubt that............. it depends on just what AA cell you refer to.

A dry or zinc cell is around 500mAh and 1.5v PD.

Whereas a NiMh can be 900-2000mAh ...some may be advertised at 3000 or more but it's crap.

Then, the mAh rate depends on the discharge rate given as the C rating. The higher the discharge rate, the less the total capacity.

Also remember these are only 1.2v per cell.

Batteryuniversity website explains all about every type of battery known, best take a visit there.

 

https://batteryuniversity.com/

[BenStark]

1 hour ago, bluejets said:

I seriously doubt that............. it depends on just what AA cell you refer to.

A dry or zinc cell is around 500mAh and 1.5v PD.

Whereas a NiMh can be 900-2000mAh ...some may be advertised at 3000 or more but it's crap.

Then, the mAh rate depends on the discharge rate given as the C rating. The higher the discharge rate, the less the total capacity.

Also remember these are only 1.2v per cell.

Batteryuniversity website explains all about every type of battery known, best take a visit there.

 

https://batteryuniversity.com/

 

An AA battery as what is available is a 1.5V Alkaline battery, and averages around 3000 mAh

 

https://www.bhphotovideo.com/c/product/1083741-REG/duracell_mn1500b20_aa_1_5v_alkaline_coppertop.html/specs

 

Duracell MN1500B20Q Specs

 

Battery Chemistry	Alkaline
Battery Voltage	1.5 V
Capacity (mAh)	2850 mAh

[Fruit Trader]

1 hour ago, BenStark said:

An AA battery as what is available is a 1.5V Alkaline battery, and averages around 3000 mAh

 

Depending on AA cell type and brand, it might even be possible to exceed 3000mAh in this very low discharge rate application.

[bluejets]

On 1/19/2024 at 11:47 AM, BenStark said:

An AA battery as what is available is a 1.5V Alkaline battery, and averages around 3000 mAh

It appears you are of the opinion the Ah rate is infinite, when in fact it is dependant on charge/discharge rate as appropriate as I have already described as the "C rate".

Best you read the whole specs from batteryuniversity.