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Blinking Leds


wandererrob

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I created a circuit for this. I wanted my LED dim enough to only be seen if you shut off all your flashlights (yes I am twisted)

I used a LED from radioshack that is pre-wired to blink. It still needed the inline resistor. I threw a 220-ohm resistor inline with a 3V lithium battery (123A) and it blinked quite brightly.

 

I experimented with increasing the resistance. I found it is still detectable in the dark even with 60k ohms inline resistance! I now have about 50k inline with a 0-10k mini potentiameter for fine tuning when i get it into the field. I put the whole package into a film can with just the led and the pot screw sticking above the rim. Then I filled the can with melted wax and let it cool. Totally waterproof and by my calculations, it should easily rn for over 5 years, depending on the amount i trim the pot screw.

 

If I was going to do it again, I would put 10k inline with a 50k pot for a wider adjustment. As it is I am worried it will be too dim with no way to brighten it. I may make another one this way, am out maybe $5 so far.

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I was kicking an idea around for a night cache that would make use of blinking LEDs.

 

My question is, where might one either get some or at least find plans to make some?

 

Long battery life would be important, which I kow is possible. My Pink Floyd - Pulse LED lasts about 3.5 years on 2 AA's. I'd be happy being able to duplicate that unit if I could. But for my purposes, the smaller the LED the better :)

 

Try here http://www.allelectronics.com/cgi-bin/cate...0/Flashing.html

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A local cache uses one of the driveway solar lamps, built into a fake rock for camo and only visible from one direction. There's a reflector trail to get you close enough to see the light. Works well!

 

(I have one in the works that uses a microcontroller to flash the LED in one of these when it gets dark. In Morse code.)

 

Some lifetime calculations:

Lithium 123A cell: about 1500mAH

Assuming 2V drop across the LED and 50k resistor, current drawn by LED: 0.02mA (is it really visible with this? Wow!)

mAH/mA: 75k hours : 8.5 years

i.e. about the same as if you left the battery out there _without_ a LED!

 

I'd've thought 1mA was about the minimum, hence only about two months lifetime, which is why I never thought of using a non-flashing LED.

Might give it a try...

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Some lifetime calculations:

Lithium 123A cell: about 1500mAH

Assuming 2V drop across the LED and 50k resistor, current drawn by LED: 0.02mA (is it really visible with this? Wow!)

mAH/mA: 75k hours : 8.5 years

i.e. about the same as if you left the battery out there _without_ a LED!

 

I think the LED can run on that small current because it is a flashing type, and it is storing the current internally in an r/c circuit until the flash.

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I am getting a little different results with the blinking LED current measurements. I have the Radio Shack 276-036 Blinking red LED. I am using 2 AA 1.5 volt alkaline batteries in series for testing. I cannot get the LED to light with an resistor in series at 10k ohms. At 5k ohms it puts out a reasonable amount of light. At 5k I measured the current with a digital meter that has peak hold and it says that the ON state draws .278 ma and the OFF state draws .017 ma. I am guessing that the difference is the type of battery, but don't have any Lithium batteries in my collection of parts.

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Place the flashing LED in a tube that is about a foot long. That way the light can only be seen from one direction.

 

I made a tube LED flasher once. I haven't put it to use, yet. I may use it in an event cache coming up. The LED and power supply are in a larger tube end. The long tube is about a foot long and ends with a cap with a 1/4 inch hole in it. The long 3/4 dia tube is lined with black flock paper.

 

The setup I use on top of my filing cabinet (linked three posts above this one) lasts for at least a month, maybe two. The frequency does not change as the 2 AAs dies but the brightness does dim. Right now I can, if I use binoculars, see it in full daylight from 0.25 miles away, at least! ;) At night it’s brilliant from 0.5 miles with the unaided eye. Adding a positive lens makes a world of difference when trying to direct and collimate the light.

 

-it

Edited by Iowa Tom
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Found something at wally world. Fake stump with face. Eyes are yellow LED. Has 2 AA NiCad, solar cell on top, and works on a photocell. 15 bucks. Hmmm.

 

Hmmm... could be worth dismantling one B)

 

What was it called? I'll do a search and see what I can find around here.

 

I'm still waiting on parts from a friend to put my evil plan into motion. B) But hey, he's sending me the stuff for free, so what can you do but wait? :lol:

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Blinking LED - I bought a blinking led with battery holder from radio shack (around $6), and changed the battery holder to hold 4 D size batteries. It lasts over one year on 4 D cells.

 

Firetacks - Get the newest ones. They are much brighter than the old 3D ones. The White ones are brightest by far. You don't notice them in the daytime....yet some cachers still have to hunt only in the daytime.

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There is a discussion on LED flashers in a non-english speaking european geocaching forum. Lots of circuit diagramms can be found there. Flashers that work for more than a year with only 2 AA cells, reactive lights that start flashing (or sending morse code) the lit with a flashlight using the LED as a light source AND light sensor and much more. Interested?

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I have used the wite and the orane firetacks and I prefer the orange. The white can still be seen in the day if the trail is well traveled. The orange tends to blend better. I actually had a cacher find one of my night caches using a huge, ridiculous flashlight in the daytime.

 

I like the discussions on the leds I have been kicking these ideas around for a few years now. I have some areas in The Ocala National Forest where people will never go without caching so I hope to follow this discussion further.

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Ive been kicking around the idea of using a battery powered outdoor string of x-mas lights for my next night cache. Would love to have LEDs. I have a timer board built and the idea is to have them flash fast for like 30 seconds and you have to count the number of each colored bulb and then do some math. If you dont finish you have to hit the button and try to finish the count again. I have a combination key holder lock that I can program the combination to and you would have to come up with the right count and math to open the lock for the next step coords inside.

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So, is there something out there that will activate by say, flashlight beam? I figure whatever it is will probably flash during the day but will be invisible to the anyone except at night. When a flashlight beam hits the sensor, it would start flashing and stop when a light source was removed.

 

The other option would be to plant a photocell somewhere to charge the batteries that will run the LED, so that it can exist indefinitely, but I would really like it to remain the ultimate stealth device until the beam hits just the right place.

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There is a discussion on LED flashers in a non-english speaking european geocaching forum. Lots of circuit diagramms can be found there. Flashers that work for more than a year with only 2 AA cells, reactive lights that start flashing (or sending morse code) the lit with a flashlight using the LED as a light source AND light sensor and much more. Interested?

 

I'd be VERY interested! :(

 

At least as much as I can read anyway.

 

EDIT: Oops! Didn't read far enough down. Thanks Radioscout! :(

Edited by wandererrob
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So, is there something out there that will activate by say, flashlight beam? I figure whatever it is will probably flash during the day but will be invisible to the anyone except at night. When a flashlight beam hits the sensor, it would start flashing and stop when a light source was removed.

 

The other option would be to plant a photocell somewhere to charge the batteries that will run the LED, so that it can exist indefinitely, but I would really like it to remain the ultimate stealth device until the beam hits just the right place.

One idea would be a reflective device of some kind that is "moved" by even the slightest wind, so that it alternated between two different [reflective] colors -

 

this would solve the:

• only active when hit with a beam

• indefinite source

• no maint. required

 

Whatcha think?? :(

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So, is there something out there that will activate by say, flashlight beam? I figure whatever it is will probably flash during the day but will be invisible to the anyone except at night. When a flashlight beam hits the sensor, it would start flashing and stop when a light source was removed.

 

The other option would be to plant a photocell somewhere to charge the batteries that will run the LED, so that it can exist indefinitely, but I would really like it to remain the ultimate stealth device until the beam hits just the right place.

 

Not sure how it would tell a flashlight beam from the sun?

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So, is there something out there that will activate by say, flashlight beam? I figure whatever it is will probably flash during the day but will be invisible to the anyone except at night. When a flashlight beam hits the sensor, it would start flashing and stop when a light source was removed.

 

The other option would be to plant a photocell somewhere to charge the batteries that will run the LED, so that it can exist indefinitely, but I would really like it to remain the ultimate stealth device until the beam hits just the right place.

 

Not sure how it would tell a flashlight beam from the sun?

 

a beam will be directed (aimed) light -

 

or it can be "covered" overhead??

 

A TUBE would defeat MY wind-enhanced idea

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OK, tell me if you guys think this is possible. Stage 1 would consist of a micro with a laser pointer, and coords for where to stand(this would be the problem point, getting everyone to stand in the exact same spot without physically marking it) This spot would be on the shore of a lake. They would have to shine the laser across the lake, hitting a mirror, which would bounce back, marking the cache location on a nearby hillside(approx. 100-150'). Was also thinking of putting a bike reflector on the tree to make it more visible. Would this be possible, or are there too many variables? This would be(of course)a night only cache.

Edited by TeamGuisinger
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OK, tell me if you guys think this is possible. Stage 1 would consist of a micro with a laser pointer, and coords for where to stand(this would be the problem point, getting everyone to stand in the exact same spot without physically marking it) This spot would be on the shore of a lake. They would have to shine the laser across the lake, hitting a mirror, which would bounce back, marking the cache location on a nearby hillside(approx. 100-150'). Was also thinking of putting a bike reflector on the tree to make it more visible. Would this be possible, or are there too many variables? This would be(of course)a night only cache.

 

ooh, cool idea. What if the coordinated guided them to a subtlely (is that a word) marked location? Or to an object that should suggest to them "this is the spot". Perhaps even an object that would help ensure proper alignment of the laser, especially if the mirror will be far away.

 

of course you've also got to make sure somehow that nobody mistakenly takes the pointer with them. :ph34r:

 

Hell, I might have to make a trip out to Ohio if you pull this one off! :ph34r:

Edited by wandererrob
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OK, tell me if you guys think this is possible.....

 

very cool idea.....

 

However, ya gotta be careful about the laser pointer & the possibility of it "pointing" other than where intended.

 

I have seen laser pointers upset people to the point where they've called the police AND I seen people LAUGH at them...

 

I guess this depends on where else it could be pointed and what else is within range of [lazer] it....

 

just my 2 cents worth of experience

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I'm not so much concerned with the sun triggering the LED flashing during the day, since it would be all but invisible, but would still like something to activate it at night, such as a flashlight beam. A secondary cell would be in place to draw charge from sunlight to keep the thing functional indefinitely. However, I could simply drop a 9V into a waterproof casing and change it out every 5 years or so.

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Lake is miles from any houses, cliff on one side. Thinking of using the cliff to mount mirror on. Also thought about setting a 4"X4" treated post with a hole or notch to set the pointer in, but would that make it too easy?

 

I don't know about that making it too easy. I mean, I suppose it does. But if you're firing a laser across a lake to hit a mirror and need it to bounce back to a specific point, the angle and placement of the laser would be critical, so some sort of alignment tool would seem reasonable, though making it less than obvious might help add some challenge.

 

You'll find though, that digging is frowned upon when placing caches or it's parts.

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