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How long bright flashing LED last on AA cells?
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William P.N. Smith
electronics forum addict


Joined: 02 Nov 2005
Posts: 80

PostPosted: Sat Jul 01, 2006 7:10 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

Jaxx <nonono@co.co.co> wrote:
Quote:
Very approximetely how long would a single super-bright red flashing LED
last?

The power source would be one (or more but how many?) rechargeable NiMH
AA cells each with a capacity of 1000 mAh?

Well, the venerable LM3903 gets a couple of years out of an alkaline D
cell, and IIRC 6 months out of an alkaline AA. Since your voltage is
lower and your amp-hours are about half, and self-discharge is much
higher in rechargables than primary cells, probably 3 months.
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Palindr☻me
electronics forum addict


Joined: 10 May 2005
Posts: 76

PostPosted: Sat Jul 01, 2006 7:12 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

Jaxx wrote:
Quote:
Very approximetely how long would a single super-bright red flashing LED
last?

The power source would be one (or more but how many?) rechargeable NiMH
AA cells each with a capacity of 1000 mAh?

If you make your own flasher electronics, using inverter techniques so
that the flasher will continue to operate until the battery is almost
totally discharged :- up to several years.


A suitable circuit will work for many days, if not weeks, from cells
normally considered "spent".

--
Sue
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Roger Hamlett
electronics forum Guru


Joined: 28 Apr 2005
Posts: 302

PostPosted: Sun Jul 02, 2006 10:36 am    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

"Jaxx" <nonono@co.co.co> wrote in message
news:Xns97F3CB17CDB991F3E91@127.0.0.1...
Quote:
Very approximetely how long would a single super-bright red flashing LED
last?

The power source would be one (or more but how many?) rechargeable NiMH
AA cells each with a capacity of 1000 mAh?
Key problem here is the words 'rechargeable NiMh'. The _self discharge_ of

many rechargeable batteries, exceeds the current consumption that the
circuit could be made to have (depends how fast you flash the light). Many
batteries of this sort, especially the high power designs, have poor
performance in this regard. This is why non rechargeable batteries are
often preferred in units designed to run for a long time.

Best Wishes
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Adam Aglionby
electronics forum beginner


Joined: 15 May 2005
Posts: 9

PostPosted: Sun Jul 02, 2006 1:09 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

Jaxx wrote:
Quote:
Very approximetely how long would a single super-bright red flashing LED
last?

The power source would be one (or more but how many?) rechargeable NiMH
AA cells each with a capacity of 1000 mAh?

AAA alkaline used in Pink Floyd`s Pulse could last a couple of years:

http://www.aume22.dsl.pipex.com/floyd/pinkfloyd.html

Adam
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Victor Roberts
electronics forum beginner


Joined: 20 Jul 2005
Posts: 40

PostPosted: Sun Jul 02, 2006 1:59 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

On Sat, 01 Jul 2006 19:57:53 +0100, Jaxx <nonono@co.co.co>
wrote:

Quote:
Very approximetely how long would a single super-bright red flashing LED
last?

The power source would be one (or more but how many?) rechargeable NiMH
AA cells each with a capacity of 1000 mAh?

I'm surprised that so many people have an answer when you
have not told us how much current this LED will draw in your
application. The life of your battery depends on the
average amount of current it must provide. While we can
guess at the duty cycle for pulse operation, the LED current
that is needed can vary by a factor of 10, 100 or even 1000
for different applications. We cannot use the term "super
bright" to determine the operating current since is not an
industry standard definition. One manufacturer's "super
bright" LED may be rated for a very different current than
"super bright" LEDs made by another company. In addition,
many of the examples given for flashing LED systems that
have very long battery life obviously run the LEDs at far
less than rated current.

Just to give one example, if you used a Lumileds Luxeon
Star, your 1000 mAh battery will last for less than 3 hours
of continuous operation, less than 12 hours if the LED is
operated at 50% duty cycle and less than 24 hours if the LED
is operated at 25% duty cycle. If, on the other hand, you
used a 20 mA LED then your 1000 mAh cell will last about 200
hours IF you run the LED at 20 mA when it is on and it is
operated at a 25% duty cycle.

To get the long operating times mentioned in previous
messages obviously requires that the LED current be far
lower than 20 mA, which I would not call "super bright".


--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.
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Palindr☻me
electronics forum addict


Joined: 10 May 2005
Posts: 76

PostPosted: Sun Jul 02, 2006 2:37 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

Victor Roberts wrote:
Quote:
On Sat, 01 Jul 2006 19:57:53 +0100, Jaxx <nonono@co.co.co
wrote:


Very approximetely how long would a single super-bright red flashing LED
last?

The power source would be one (or more but how many?) rechargeable NiMH
AA cells each with a capacity of 1000 mAh?


I'm surprised that so many people have an answer when you
have not told us how much current this LED will draw in your
application. The life of your battery depends on the
average amount of current it must provide. While we can
guess at the duty cycle for pulse operation, the LED current
that is needed can vary by a factor of 10, 100 or even 1000
for different applications. We cannot use the term "super
bright" to determine the operating current since is not an
industry standard definition. One manufacturer's "super
bright" LED may be rated for a very different current than
"super bright" LEDs made by another company. In addition,
many of the examples given for flashing LED systems that
have very long battery life obviously run the LEDs at far
less than rated current.

Just to give one example, if you used a Lumileds Luxeon
Star, your 1000 mAh battery will last for less than 3 hours
of continuous operation, less than 12 hours if the LED is
operated at 50% duty cycle and less than 24 hours if the LED
is operated at 25% duty cycle. If, on the other hand, you
used a 20 mA LED then your 1000 mAh cell will last about 200
hours IF you run the LED at 20 mA when it is on and it is
operated at a 25% duty cycle.

To get the long operating times mentioned in previous
messages obviously requires that the LED current be far
lower than 20 mA, which I would not call "super bright".


No. As you start by saying, operating time does depend on the average

current (and self-discharge rates). A long operating time can be
achieved with the LED current at 20mA or more when on, if the duty cycle
is low enough. A very low duty cycle is pretty common for a flashing LED
running from a battery supply.

Making a small inductor the load of a multivibrator oscillator, with the
LED in parallel with it, can produce a train of "super bright" flashes
even from a supply of <1v.

--
Sue



--
Sue
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Clive Mitchell
electronics forum beginner


Joined: 25 Mar 2005
Posts: 18

PostPosted: Sun Jul 02, 2006 6:07 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

In message <1151845761.000510.49430@m73g2000cwd.googlegroups.com>, Adam
Aglionby <ledlight@gmail.com> writes
Quote:
AAA alkaline used in Pink Floyd`s Pulse could last a couple of years:

http://www.aume22.dsl.pipex.com/floyd/pinkfloyd.html

Looks like the humble LM3909 which is obsolete now. Quite an expensive
assembly for an album novelty.

Ironically it's cheaper to use a microprocessor now. You set the
watchdog to wake the processor up after a specific delay and the program
consists of turning the LED on, running a short blink time delay,
turning the LED off and going to sleep. The watchdog resets the
processor and it starts again. You can set the LED current (resistor) on
time and off time as desired.

Does require more than one battery though.


--
Clive Mitchell
http://www.bigclive.com
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Victor Roberts
electronics forum beginner


Joined: 20 Jul 2005
Posts: 40

PostPosted: Sun Jul 02, 2006 6:12 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

On Sun, 02 Jul 2006 15:37:34 +0100, Palindr?me
<me9@privacy.net> wrote:

Quote:
Victor Roberts wrote:
On Sat, 01 Jul 2006 19:57:53 +0100, Jaxx <nonono@co.co.co
wrote:


Very approximetely how long would a single super-bright red flashing LED
last?

The power source would be one (or more but how many?) rechargeable NiMH
AA cells each with a capacity of 1000 mAh?


I'm surprised that so many people have an answer when you
have not told us how much current this LED will draw in your
application. The life of your battery depends on the
average amount of current it must provide. While we can
guess at the duty cycle for pulse operation, the LED current
that is needed can vary by a factor of 10, 100 or even 1000
for different applications. We cannot use the term "super
bright" to determine the operating current since is not an
industry standard definition. One manufacturer's "super
bright" LED may be rated for a very different current than
"super bright" LEDs made by another company. In addition,
many of the examples given for flashing LED systems that
have very long battery life obviously run the LEDs at far
less than rated current.

Just to give one example, if you used a Lumileds Luxeon
Star, your 1000 mAh battery will last for less than 3 hours
of continuous operation, less than 12 hours if the LED is
operated at 50% duty cycle and less than 24 hours if the LED
is operated at 25% duty cycle. If, on the other hand, you
used a 20 mA LED then your 1000 mAh cell will last about 200
hours IF you run the LED at 20 mA when it is on and it is
operated at a 25% duty cycle.

To get the long operating times mentioned in previous
messages obviously requires that the LED current be far
lower than 20 mA, which I would not call "super bright".


No. As you start by saying, operating time does depend on the average
current (and self-discharge rates). A long operating time can be
achieved with the LED current at 20mA or more when on, if the duty cycle
is low enough. A very low duty cycle is pretty common for a flashing LED
running from a battery supply.

What duty cycle would you use?

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.
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Adam Aglionby
electronics forum beginner


Joined: 15 May 2005
Posts: 9

PostPosted: Sun Jul 02, 2006 9:40 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

Clive Mitchell wrote:
Quote:
In message <1151845761.000510.49430@m73g2000cwd.googlegroups.com>, Adam
Aglionby <ledlight@gmail.com> writes
AAA alkaline used in Pink Floyd`s Pulse could last a couple of years:

http://www.aume22.dsl.pipex.com/floyd/pinkfloyd.html

Looks like the humble LM3909 which is obsolete now. Quite an expensive
assembly for an album novelty.

Used to have one lying around AFAIR it was a LM3909, on a short pulse
long break cycle.

Build quality was nice for a CD box, but novelty sleeves are much rarer
nowadays with smaller artwork space, lensatic 3D Raven LP by the
Stranglers was another nice one. Soft rock group made a shaped disc in
shape of Africa the continent, problem was Cape Horn jammed on some
turntables tone arm pivot.

Adam
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Spehro Pefhany
electronics forum Guru


Joined: 01 May 2005
Posts: 2326

PostPosted: Sun Jul 02, 2006 10:13 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

On Sun, 02 Jul 2006 18:07:03 GMT, the renowned Clive Mitchell
<bigclive1@ntlworld.com> wrote:

Quote:
In message <1151845761.000510.49430@m73g2000cwd.googlegroups.com>, Adam
Aglionby <ledlight@gmail.com> writes
AAA alkaline used in Pink Floyd`s Pulse could last a couple of years:

http://www.aume22.dsl.pipex.com/floyd/pinkfloyd.html

Looks like the humble LM3909 which is obsolete now. Quite an expensive
assembly for an album novelty.

There was a Logictech mouse sold some years ago with a flashing LED in
the box. It used two very nice AA Ultra Duracells in conjuction with a
little COB assembly-- a CMOS ASIC under the epoxy. Just three
additional parts- the LED itself and two resistors to set frequency
and LED current. Duty cycle fixed. Output was an NMOS open-drain with
about 18 ohms Rds(on) typical.

BTW, despite the voltage doubling drive circuit, the LM3909 was not
capable of driving many modern non-red LEDs from a single 1.5V cell
because of the low output voltage.

Quote:
Ironically it's cheaper to use a microprocessor now.

For hobbyists anyway.

Quote:
You set the
watchdog to wake the processor up after a specific delay and the program
consists of turning the LED on, running a short blink time delay,
turning the LED off and going to sleep. The watchdog resets the
processor and it starts again. You can set the LED current (resistor) on
time and off time as desired.

Does require more than one battery though.

I don't know of any flash parts that have an on-chip voltage doubler,
but there are plenty of mask-programmed micros and ASICs. I'd love to
hear of any mask programmed parts..


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
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Palindr☻me
electronics forum addict


Joined: 10 May 2005
Posts: 76

PostPosted: Mon Jul 03, 2006 8:33 am    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

Victor Roberts wrote:
Quote:
On Sun, 02 Jul 2006 15:37:34 +0100, Palindr?me
me9@privacy.net> wrote:


Victor Roberts wrote:

On Sat, 01 Jul 2006 19:57:53 +0100, Jaxx <nonono@co.co.co
wrote:



Very approximetely how long would a single super-bright red flashing LED
last?

The power source would be one (or more but how many?) rechargeable NiMH
AA cells each with a capacity of 1000 mAh?


I'm surprised that so many people have an answer when you
have not told us how much current this LED will draw in your
application. The life of your battery depends on the
average amount of current it must provide. While we can
guess at the duty cycle for pulse operation, the LED current
that is needed can vary by a factor of 10, 100 or even 1000
for different applications. We cannot use the term "super
bright" to determine the operating current since is not an
industry standard definition. One manufacturer's "super
bright" LED may be rated for a very different current than
"super bright" LEDs made by another company. In addition,
many of the examples given for flashing LED systems that
have very long battery life obviously run the LEDs at far
less than rated current.

Just to give one example, if you used a Lumileds Luxeon
Star, your 1000 mAh battery will last for less than 3 hours
of continuous operation, less than 12 hours if the LED is
operated at 50% duty cycle and less than 24 hours if the LED
is operated at 25% duty cycle. If, on the other hand, you
used a 20 mA LED then your 1000 mAh cell will last about 200
hours IF you run the LED at 20 mA when it is on and it is
operated at a 25% duty cycle.

To get the long operating times mentioned in previous
messages obviously requires that the LED current be far
lower than 20 mA, which I would not call "super bright".



No. As you start by saying, operating time does depend on the average
current (and self-discharge rates). A long operating time can be
achieved with the LED current at 20mA or more when on, if the duty cycle
is low enough. A very low duty cycle is pretty common for a flashing LED
running from a battery supply.


What duty cycle would you use?

It depends on the application Smile


For example:

For a torch with a super bright LED running off a single cell, I would
probably have an adjustable duty cycle from 5 - 50%. That would give
adjustable brightness (and run-time).

For a "walker on road setting", one 10 mSec flash, 3 times a second.
Cyclically varying the repetition rate is more likely to get it seen.

For a "power on" indicator where power is limited, one 5mSec flash every
10 secs is a starting point.

--
Sue
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Victor Roberts
electronics forum beginner


Joined: 20 Jul 2005
Posts: 40

PostPosted: Mon Jul 03, 2006 1:52 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

On Mon, 03 Jul 2006 09:33:00 +0100, Palindr?me
<me9@privacy.net> wrote:

Quote:
Victor Roberts wrote:
On Sun, 02 Jul 2006 15:37:34 +0100, Palindr?me

[snip]

Quote:
What duty cycle would you use?

It depends on the application :)

For example:

For a torch with a super bright LED running off a single cell, I would
probably have an adjustable duty cycle from 5 - 50%. That would give
adjustable brightness (and run-time).

For a "walker on road setting", one 10 mSec flash, 3 times a second.
Cyclically varying the repetition rate is more likely to get it seen.

For a "power on" indicator where power is limited, one 5mSec flash every
10 secs is a starting point.

That's quite a large duty cycle range. 50% to 0.05% or a
range of 1000. Which do you think the OP was referring to
when he asked about his battery life?

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.
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Palindr☻me
electronics forum addict


Joined: 10 May 2005
Posts: 76

PostPosted: Mon Jul 03, 2006 3:05 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

Victor Roberts wrote:
Quote:
On Mon, 03 Jul 2006 09:33:00 +0100, Palindr?me
me9@privacy.net> wrote:


Victor Roberts wrote:

On Sun, 02 Jul 2006 15:37:34 +0100, Palindr?me


[snip]


What duty cycle would you use?


It depends on the application :)

For example:

For a torch with a super bright LED running off a single cell, I would
probably have an adjustable duty cycle from 5 - 50%. That would give
adjustable brightness (and run-time).

For a "walker on road setting", one 10 mSec flash, 3 times a second.
Cyclically varying the repetition rate is more likely to get it seen.

For a "power on" indicator where power is limited, one 5mSec flash every
10 secs is a starting point.


That's quite a large duty cycle range. 50% to 0.05% or a
range of 1000. Which do you think the OP was referring to
when he asked about his battery life?

If he had to ask the question posed, I shouldn't imagine that he knew

either.

All that was clear was that he wanted a bright LED to flash and wanted
to power it from, ideally one, but if necessary more, AA NiMH cells -
and was concerned how long it would keep flashing. The logical inference
was that he wanted it to flash for as long as possible.

He know knows that, if he wants, he can keep the LED flashing for months
of a single AA NiMH cell...which I think rather answers his question.
Perhaps. ;)

--
Sue
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Clive Mitchell
electronics forum beginner


Joined: 25 Mar 2005
Posts: 18

PostPosted: Mon Jul 03, 2006 11:56 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

In message <12aichk5ihf6509@corp.supernews.com>,
=?UTF-8?B?UGFsaW5kcuKYu21l?= <me9@privacy.net> writes
Quote:
All that was clear was that he wanted a bright LED to flash and wanted
to power it from, ideally one, but if necessary more, AA NiMH cells -
and was concerned how long it would keep flashing. The logical
inference was that he wanted it to flash for as long as possible.

He know knows that, if he wants, he can keep the LED flashing for
months of a single AA NiMH cell...which I think rather answers his
question. Perhaps. Wink

I'll have a guess at the application.....

They probably wanted to add a flashing LED to a fake camera that could
run for a long time on a battery.

In reality, a short duty cycle blinking LED on a camera immediately says
FAKE! :)

--
Clive Mitchell
http://www.bigclive.com
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Lostgallifreyan
electronics forum Guru Wannabe


Joined: 13 Apr 2006
Posts: 241

PostPosted: Tue Jul 04, 2006 12:17 am    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

Clive Mitchell <bigclive1@ntlworld.com> wrote:
Quote:
In message <12aichk5ihf6509@corp.supernews.com>,
=?UTF-8?B?UGFsaW5kcuKYu21l?= <me9@privacy.net> writes
All that was clear was that he wanted a bright LED to flash and wanted
to power it from, ideally one, but if necessary more, AA NiMH cells -
and was concerned how long it would keep flashing. The logical
inference was that he wanted it to flash for as long as possible.

He know knows that, if he wants, he can keep the LED flashing for
months of a single AA NiMH cell...which I think rather answers his
question. Perhaps. ;)

I'll have a guess at the application.....

They probably wanted to add a flashing LED to a fake camera that could
run for a long time on a battery.

In reality, a short duty cycle blinking LED on a camera immediately says
FAKE! :)



If that's true, it won't deter a thief. Bear with me here, the logic gets
interesting.. >:)

If it won't deter a thief, it's very important that cameras with flashing LED's
on them actually contain lenses and working circuits to gather video evidence
of the events that they might seem to encourage. Therefore it makes sense to
always have something real in there, so in practise, you'd be wrong. :)

In the end it comes down to two types of criminal (occupying various points on
a single line continuum actually). Smart, and dumb. The smart ones will think
this logic through and know that there is no easy guide, a small stub sticking
out the top might be a radio aerial that sends a keep-alive pulse that would
set an alarm off if it was sabotaged to prevent transmission, so a lack of
wires would deter a smart criminal, but not a very stupid one.

So, the LED makes sense, it will deter the smart ones, who will usually have
easier ways to make a dishonest living, and there's not much you can do about
the dumb ones, they're hard to predict. They're usually opportunists though, so
if everything else looks like a deterrent too, they'll leave well alone. I've
had an empty bell-box on a wall over my window for 20 years, and it works, I've
even overheard discussions outside once, and the general tenor was one of
nervous defiance, but the nervousness won out.

If it looks like a duck, how long do you wait to see if it quacks like a duck?
The longer you wait, the more uncertain you get, and uncertainty undermines
resolve, especially of criminals.

And that, ladies and gentlemen, ends my self-amusing rant for the day. >Smile
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