FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   PreferencesPreferences   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Forum index » Electronix » components
How long bright flashing LED last on AA cells?
Post new topic   Reply to topic Page 3 of 3 [43 Posts] View previous topic :: View next topic
Goto page:  Previous  1, 2, 3
Author Message
Lostgallifreyan
electronics forum Guru Wannabe


Joined: 13 Apr 2006
Posts: 241

PostPosted: Wed Jul 05, 2006 6:39 am    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

William P.N. Smith <news2006c@compusmiths.com> wrote in
news:7soka2tvbdm8bk7t2ge1h2ckpbuqiph2no@4ax.com:

Quote:
Lostgallifreyan <no-one@nowhere.net> wrote:
If it looks like a duck, how long do you wait to see if it quacks like
a duck?

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94030
works remarkably well, it senses motion and scans while flashing a
light.


Nice. Judging by the combination of visceral response to physical action,
and the fact that few people other than the builders of such things can
separate the practical requirements for that kind of machine vision, and
that needed for recording images, that thing should deter criminals both
smart and dumb.
Back to top
Lostgallifreyan
electronics forum Guru Wannabe


Joined: 13 Apr 2006
Posts: 241

PostPosted: Wed Jul 05, 2006 6:54 am    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

William P.N. Smith <news2006c@compusmiths.com> wrote in
news:psqka2ha2giiv7ir3n5oljfiijtkrol749@4ax.com:

Quote:
Lostgallifreyan <no-one@nowhere.net> wrote:
Doesn't matter though, there are two ways to go, either demand exact
specs from someone who might not have a clear idea yet, or post a
response based on your own carefully judged assumption.

Yeah, what "Lost" said.

Lastly, consider a low power laser diode, UNLENSED. These are eye safe
at distances beyond a few inches, (take care NOT to use a microlensed
version though) as they diverge strongly. Their output is highly
monochromatic, specular, very eye-catching, and their conversion of
electricity to light is second to none, so they can make ideal
beacons.

This sounds interesting, do you have any sources?

Thanks!

[I think the discussion engendered by this particular "How long a
piece of string?" query has been useful and enlightening [sic].]


Agreed. Smile 'Nospam', we do it for us. It amuses, interests... There are
ters questions with terse answers with immensely high SNR for those
involved, but they are often so specific that they offer nothing to anyone
but those who ask and answer. When a few people get to put in ideas threads
get interesting to many at once. Some verge on the inane but I don't care,
I take as I find it, I don't have to read them all. :)

William, there's laser diodes from roithner-laser.com, intellite.com, and
if you're in the UK, photonic-products.com have some especially nice ones
made by Opnext (Hitachi). Sometimes the most cost effective way is eBay,
seller milasers (Meredith Instruments) was selling boxes of 100 5 mW 635 nm
5.6 mm packaged diodes. They want around 45 to 70 mA to get full output,
but pulsed, these could form excellent small beacons, extremely visible as
the wavelength is a lot shorter than most red LED's. Even unlensed, a
distance of a few feet is wise if you're going to look into them directly.
Lensed to collimate parallel, that should not be done at all. Nice
advantage: collimated, you can project the beacon on a high wall or post
without the expense of wires. Totally weatherproof too, that way.
Back to top
Palindr☻me
electronics forum addict


Joined: 10 May 2005
Posts: 76

PostPosted: Wed Jul 05, 2006 7:00 am    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

Lostgallifreyan wrote:
Quote:
William P.N. Smith <news2006c@compusmiths.com> wrote in
news:7soka2tvbdm8bk7t2ge1h2ckpbuqiph2no@4ax.com:


Lostgallifreyan <no-one@nowhere.net> wrote:

If it looks like a duck, how long do you wait to see if it quacks like
a duck?

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94030
works remarkably well, it senses motion and scans while flashing a
light.



Nice. Judging by the combination of visceral response to physical action,
and the fact that few people other than the builders of such things can
separate the practical requirements for that kind of machine vision, and
that needed for recording images, that thing should deter criminals both
smart and dumb.

LOL, you might think so. However, around here, all of these fake cameras
are the same make and model and crims can easily identify one and all.

One idea is to take some of these fake cameras and retrofit real camera
modules. The crims will treat them as fakes and operate quite openly in
front of them, rather than try and find somewhere not covered by a camera..

Of course, all you have to do is spread the rumour that this has been
done..and then not bother..

etc..
--
Sue
Back to top
Clive Mitchell
electronics forum beginner


Joined: 25 Mar 2005
Posts: 18

PostPosted: Wed Jul 05, 2006 9:39 am    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

In message <Xns97F74DF502A5Dzoodlewurdle@140.99.99.130>, Lostgallifreyan
<no-one@nowhere.net> writes
Quote:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94030
works remarkably well, it senses motion and scans while flashing a
light.


Nice. Judging by the combination of visceral response to physical
action, and the fact that few people other than the builders of such
things can separate the practical requirements for that kind of machine
vision, and that needed for recording images, that thing should deter
criminals both smart and dumb.

No. It looks completely fake and will drain the batteries quickly with
it's prolonged motorised sweeping movement.

Although it uses light level movement sensing it does trigger easily. I
got a couple cheap and took 'em to bits. (As I tend to do.)

--
Clive Mitchell
http://www.bigclive.com
Back to top
William P.N. Smith
electronics forum addict


Joined: 02 Nov 2005
Posts: 80

PostPosted: Wed Jul 05, 2006 12:28 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

Lostgallifreyan <no-one@nowhere.net> wrote:
Quote:
William, there's laser diodes from roithner-laser.com, intellite.com

Many thanks!
Back to top
Jax
electronics forum beginner


Joined: 16 Jan 2006
Posts: 6

PostPosted: Wed Jul 05, 2006 12:41 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

On 03 Jul 2006, =?UTF-8?B?UGFsaW5kcuKYu21l?=<me9@privacy.net> wrote:

Quote:
Victor Roberts wrote:
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.


As OP, I can say there is some truth in that. I want the flash rate to
be one that is noticed but I would have to try it out in real life to
see which rate worked best for me.

What I really wanted to know was whether an NIMH was going to give me
such a short life (say under 4 days) that I would be better using a
mains PSU. This is an outdoor application so a battery setup has quite
a lot of advantages from portability and wider choice of location.


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
Back to top
Jax
electronics forum beginner


Joined: 16 Jan 2006
Posts: 6

PostPosted: Wed Jul 05, 2006 12:45 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

On 04 Jul 2006, 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! :)


As OP I can say that's not quite it but it is reasonably close in
principle to what I had in mind.

In fact, the flashing is not for humans to notice though but for
animals. That's why I am vague about the correct flash rate.
Back to top
Jax
electronics forum beginner


Joined: 16 Jan 2006
Posts: 6

PostPosted: Wed Jul 05, 2006 12:47 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

On 05 Jul 2006, Clive Mitchell<bigclive1@ntlworld.com> wrote:

Quote:
In message <Xns97F74DF502A5Dzoodlewurdle@140.99.99.130>,
Lostgallifreyan <no-one@nowhere.net> writes
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=
9
4030 works remarkably well, it senses motion and scans while
flashing a light.


Nice. Judging by the combination of visceral response to physical
action, and the fact that few people other than the builders of
such things can separate the practical requirements for that kind
of machine vision, and that needed for recording images, that thing
should deter criminals both smart and dumb.

No. It looks completely fake and will drain the batteries quickly
with it's prolonged motorised sweeping movement.

Although it uses light level movement sensing it does trigger
easily. I got a couple cheap and took 'em to bits. (As I tend to
do.)

The price of real cameras seems to be falling so much that a very
basic "starter" real camera is not all that much more expensive than
a dummy.

It's perhaps true that the cheaper sort of real camera look even more
fake than the fake cameras do.
Back to top
Palindr☻me
electronics forum addict


Joined: 10 May 2005
Posts: 76

PostPosted: Wed Jul 05, 2006 12:53 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

Jaxx wrote:
Quote:
On 04 Jul 2006, Clive Mitchell<bigclive1@ntlworld.com> wrote:


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! :)



As OP I can say that's not quite it but it is reasonably close in
principle to what I had in mind.

In fact, the flashing is not for humans to notice though but for
animals. That's why I am vague about the correct flash rate.

You might want to consider some CMOS low power internally linked shift
registers, to give a pseudo-random variable flash rate.

It puzzles the heck out of my squirrels, when connected to a motorised
table. They can manage up to 3 bits of this "Simon" memory game,
correctly jumping to the table at the correct time. But not 4 bits.

--
Sue
Back to top
Jax
electronics forum beginner


Joined: 16 Jan 2006
Posts: 6

PostPosted: Wed Jul 05, 2006 12:53 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

On 04 Jul 2006, Don Klipstein<don@manx.misty.com> wrote:
Quote:

I have some ideas...

1. If this is to be used in the home, power the LED from a wall
wart. And maybe power the LED through two steering diodes coming
together - one from the wall wart and the other from a backup
battery.

For that matter, get the cheapest actual security camera you can
find from a hobbyist/surplus catalog - even if it's incompatible
with anything practical.

Or further for that matter, find some little professional looking
case and fit some cheap webcam into it and you have a fake security
camera that may actually be made to work in some way as a real one!
Put a red LED on the case...

2. I have an idea for the red LED - make it glow continuously like
those on real cameras that have LEDs do. Get a GaAlAsP red LED,
peak wavelength 660 nm, 3000 mcd (with a usual beam width of 15
degrees but sometimes claimed more), such as Radio Shack 276-307.
Red LEDs of same/similar chemistry and efficiency are Agilent
HLMP-8103 and HLMP-C124.

Get some fine sandpaper and sand down the tip by about a millimeter
then restore the "bullet" shape but about a millimeter shorter and
with the tip very slightly more blunt, then get some really fine
sandpaper and get the LED good and evenly frosted. After that, you
have a super high efficiency diffused wide angle red LED that works
well and reliably at 1 milliamp, and may be bright enough at half a
milliamp. It will glow with a color close enough to that of lower
efficiency red LEDs.

If you really want to go all out, get an InGaN green LED (nominal
wavelength usually 525 to 530 nm) of the common 5 mm "bullet" style
and give it the sandpaper treatment described above. Then give it
half a milliamp or maybe a quarter of a milliamp. Most Nichia 5 mm
green ones and those trying to compete with them (ETG, and others)
should at half a milliamp have a brightness that I consider "fully
that of a usual green LED indicator light". Furthermore, the
wavelength of these tends to shift a little inversely with current,
and at half a milliamp the color is likely to be about that of LEDs
with nominal wavelength in the 550's nm, maybe close to 560 - a
yellowish shade of green likely to look enough like a usual 565 nm
green LED indicator lamp to look like a usual indicator LED to most
criminals.

A pack of (4) AA alkaline cells with a 6.8K resistor should power
such a green LED reasonably well 24/7 for at least half a year.

If you want an LED to falsely indicate presence of a security
system in an automobile, don't worry about conserving every
milliamp since the battery has self-discharge in the 10's of
milliamps. You can afford a few milliamps to protect a car.

- Don Klipstein (don@misty.com)



There are some nice hints and tips above which I had not thought of,
Such as filing down LED case to extract more light.
Back to top
Jax
electronics forum beginner


Joined: 16 Jan 2006
Posts: 6

PostPosted: Wed Jul 05, 2006 12:56 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

On 05 Jul 2006, JohnR66<nospam@att.net> wrote:

Quote:
"Jaxx" <nonono@co.co.co> wrote in message
news:Xns97F3CB17CDB991F3E91@127.0.0.1...
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?

You asked how long the LED would last. Did you mean whow long the
batteries would last?

Yes! Oh, you are so literal!

But in fairness you are also very correct.

Quote:

The LED can last a second to many years depending on the dropping
resistor or the lack thereof.
John
Back to top
Clive Mitchell
electronics forum beginner


Joined: 25 Mar 2005
Posts: 18

PostPosted: Wed Jul 05, 2006 6:01 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

In message <12andhrtkrbcga2@corp.supernews.com>,
=?UTF-8?B?UGFsaW5kcuKYu21l?= <me9@privacy.net> writes
Quote:
You might want to consider some CMOS low power internally linked shift
registers, to give a pseudo-random variable flash rate.

Another task begging for a cheap microcontroller..... A PIC 12F629
comes to mind. Eight pin chip and it does the LOT.

--
Clive Mitchell
http://www.bigclive.com
Back to top
Jaxx
electronics forum beginner


Joined: 01 Jul 2006
Posts: 2

PostPosted: Wed Jul 12, 2006 7:45 pm    Post subject: Re: How long bright flashing LED last on AA cells? Reply with quote

On 04 Jul 2006, William P.N. Smith<news2006c@compusmiths.com> wrote:

Quote:
nospam <nospam@please.invalid> wrote:
A third and the easiest way to go is ignore dumb questions like "I
have an application for some string, what length do I need?".

Thank you for your input.



I was going to thank him for his output. Smile
Back to top
Google

Back to top
Display posts from previous:   
Post new topic   Reply to topic Page 3 of 3 [43 Posts] Goto page:  Previous  1, 2, 3
View previous topic :: View next topic
The time now is Tue Aug 22, 2017 3:36 am | All times are GMT
Forum index » Electronix » components
Jump to:  

Similar Topics
Topic Author Forum Replies Last Post
No new posts Measure long distance using ultrasonic sensor thieunguyen design 0 Wed Nov 19, 2008 5:34 pm
No new posts long distance (5 miles) wireless communication CMOS design 4 Fri Jul 14, 2006 5:42 am
No new posts How long does MP3 flash memory retain contents? Jon D components 10 Thu Jul 06, 2006 12:16 pm
No new posts charging four 1.5 V cells using, Col Sanjeev Devasthali Basics 2 Sun Jun 25, 2006 12:14 pm
No new posts charging 4 ni-cd 1.5 v cells Col Sanjeev Devasthali design 7 Sun Jun 25, 2006 12:12 pm

Copyright © 2004-2005 DeniX Solutions SRL
Other DeniX Solutions sites: Unix/Linux blog |  Unix/Linux documentation |  Unix/Linux forums |  Medicine forum |  Science forum  |  Send and track newsletters


Powered by phpBB © 2001, 2005 phpBB Group