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Night Caches


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There are several night-caches here in the Phoenix area, due to our lovely summer climate (you could hike at 115 degrees in the day or 95 at night- the choice is obvious)...anyway I have seen some that require portable blacklights to find phosphorescent nano caches. I have been itching to make a multi cache where the coords are written with a UV pen - not only to prevent muggle interest, but for the cool factor. Im also thinking about LED's and making motion sensing, blinking caches that will be hidden out in the desert....

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I know about this one, I haven't been to it yet though.

 

When Darkness Falls.......

 

Saving it for the Fall though, because the park closes at 11 pm, and I'd be rushed after dark right now to find it. Besides, I'm thinking it'll be fun to do around halloween ;)

 

That's one thing to consider when placing night caches in parks though, some don't stay open after dark (hence the posted sings, only open sunrise to sunset), so make sure to pick an area where it's okay.

 

BTW, loved the idea on the Halo theme!

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This is one of those topics that come up from time to time:

 

Night Caches, How do you search for them at geocaching

How about a special icon & status for Night Caches?

Night Caches

Night Caches

 

Personally, three of my favorites caches were night caches. They were all based on constellations. It took us one failed attempt before we got the hang of them. LOADS of fun.

 

Cassiopeia

Ursa Minor

The Big Dipper

 

I did these in the winter but accompanied a friend when she did them in the summer....as with this topic, doing them in the winter was a lot more fun! ^_^

 

Bret

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I have placed a nightime only cache that uses deer trail reflectors. Basically "FireTracks" but a different name brand. I picked them up at Academy Sports. There are a couple other night caches in the area that I know of, and they both also use the reflectors. They work well enough, but I am sure interested in some breakthrough idea that still requires night caching.

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Just reading this (and the older threads linked earlier) gives me some ideas, maybe one in time for Saturday's meet and greet. There's no caches anywhere like this near here. Maybe it's time to place a few.

 

I've used reflective safety tape like used to mark the sides of an 18 wheeler in the brush before, but I really like the FireTack idea. Reading between the lines on the site, these seem like they are small corner prism retroreflectors with the incredible brightness and contamination resistance but without Edmund Optics' prices. I'd bet a laser pen pointer could light one up several miles away (if you can hit it). Looks like a toy to acquire a handful of, and not just for geocaching.

 

Great swag "trade-up" idea too - LOL.

 

On the UV light sources - Several electronic surplus places have ultraviolet LEDs with wavelengths in the low 400 nanometer to upper 300 nanometer. Thanks to gallium nitride which gave us the blue LEDs, fairly powerful handheld UV sources are now available.

 

They take about 4 volts forward voltage and current regulation to make them work, and they ARE static sensitive, so you have to wear an ESD grounding wrist strap and use a grounded soldering iron to assemble anything that uses them.

 

For those of us electronics geeks who like to build stuff, here's some catalog sources:

All Electronics Corp

BG Micro

Alltronics

Electronic Goldmine

MPJA

 

In the past I used to hunt scorpions at night (they fluoresce) with an 18 inch UV tube in a 120 volt fixture mounted on a piece of 2x6, with a 200 watt AC inverter duct-taped to the back, and a 7 ampere-hour gel cell to power the inverter in a fanny pack. I cut some coffee cans lengthwise to make a reflector so the UV was projected forward. It was heavy and bulky, but it worked.

 

So a solid state UV flashlight is something on the "projects to build" list (might be next winter before it happens)

 

An avid spelunker showed me a nifty headlamp at Field Day. It has 7 white LEDs and performed as well as my 3 cell Mag-Lite.

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oooohhh....you could have a small solar-powered IR LED blinker- that can only be found with night vision, digital camera, or camcorder....

(digging in electronics junk drawer) Hmmm - 880nm LEDs, 4.7K surface mount resistors, 8 pin microcontroller that runs for months on a hearing aid battery, NiMH pack, several loose solar cells... (evil grin)

 

How about a pigment that fluoresces under UV light but emits only at about 820 nanometers and just absorbs everything else.. Hmmm - a wavelength doubler / frequency halving substance - 400 nanometers in, 800 nanometers out. And make a retroreflector out of the stuff...

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oooohhh....you could have a small solar-powered IR LED blinker- that can only be found with night vision, digital camera, or camcorder....

(digging in electronics junk drawer) Hmmm - 880nm LEDs, 4.7K surface mount resistors, 8 pin microcontroller that runs for months on a hearing aid battery, NiMH pack, several loose solar cells... (evil grin)

 

Now if only I had some idea of how to actually put that together ! ^_^ Electronics are not among my bag of tricks, but I LOVE this idea. Any chance you could send me the specs for that ? The techs at work like building stuff like that on their "breaks" :P

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I made a cache that can only be done in the dark.

The Dark Side

 

Two pictures showing the reflector viewable at night and not viewable by day.

6a92f4da-b9de-41e6-a04a-ad9381ba3143.jpg

d7ec476f-26cf-48b1-b82c-e98ce6152747.jpg

 

The daylight one is taken about 10m further back, but you can see the same trees in the background. The reflector is UP THE TREE, not the ones on my MTB.

PS - forgot to add - in a Eucalyptus forest with the trunks the mottled white effect, this is very effective at being invisible during the day.

Edited by mtbikeroz
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oooohhh....you could have a small solar-powered IR LED blinker- that can only be found with night vision, digital camera, or camcorder....

Anyone have any ideas where you might get one of these? And/or would they be affordable? And/or would it really work with like just like video cameras with infared and stufF?

 

I went out to Gander Mountain the other day and bought a few boxes of generic fire tacks, but the whole idea seems lame and used (even though there aren't any night caches in my area)

 

The whole infared idea sounds cool to me...

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Now if only I had some idea of how to actually put that together ! :lol: Electronics are not among my bag of tricks, but I LOVE this idea. Any chance you could send me the specs for that ? The techs at work like building stuff like that on their "breaks" :unsure:

Sounds like a great idea. I need to actually draw the schematic and try and size the battery and solar cell so it can charge enough in a short day to wink all night.

 

Or, maybe only wink a few hours after sunset on December 21st or after an overcast day. Otherwise:

 

Joe Spoiler found it "Easy find in daylight - just look for the solar panel poking out of the south side of the big tree, then follow the wires down to the fake stump." :-)

 

--- Solar cells are kinda finicky - just the shadow of a branch falling on an array cuts the power by more than half. A solar charging system has to be sized to collect enough energy on an overcast day December 21st to power the equipment until after sunrise on the 22nd.

 

However - since such a critter doesn't need to blink during the day, it can stay dormant and use 100% of the collected energy to charge the battery, and only once the solar cell output totally goes away it can start blinking.

 

I'm thinking a 50 to 100 ms flash of the LED every 5 seconds would keep it challenging - someone would have to carefully move the night vision scope only a few degrees and wait to finally acquire the signal.

 

50 milliseconds would permit a video camera to complete just over 3 full frame scans while the LED was on.

 

Or the pulses could be made even shorter, so one might have to wait a minute or two before capturing a good one.

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hmm- ya know what else would be cool- have a RF beacon- sorta like a radio sonar...you get close to the cache- emit a RF ping, and you get a chirp back- and have the cache entirely hidden with the exception of the antenna. ooh- yo could have some sweet techno-caches. I think this topic is worthy of it's own thread...

Low enough power might make for an interesting foxhunt.

 

Hmmm - RFID tags do that, only work at a few feet, and use the transmitted signal to ping them as a power source.

 

I've seen some ordinary hidden transmitters that are truly wicked hides. Not to mention playing with the antenna and power levels to confuse folks once they get really close.

 

Nastiest one I've read about was a barbed wire coil that snaked through the brush. It happened to have the right diameter and spacing to form a circularly polarized helical antenna that was aimed right at a mountainside a couple of miles across the canyon. People would home in on the distant mountainside, climb up there, and then get a solid bearing back the other direction.

 

But an active geocache. Hmmm - ping it on 70cm, listen for a 1/2 milliwatt reply for 2 seconds on 2 meters.

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oooohhh....you could have a small solar-powered IR LED blinker- that can only be found with night vision, digital camera, or camcorder....

Anyone have any ideas where you might get one of these? And/or would they be affordable? And/or would it really work with like just like video cameras with infared and stufF?

 

I went out to Gander Mountain the other day and bought a few boxes of generic fire tacks, but the whole idea seems lame and used (even though there aren't any night caches in my area)

 

The whole infared idea sounds cool to me...

You'd have to build one, I think.

 

Really high brightness infrared LED that can be pulsed, microcontroller (like the PIC12F series - 8 pin part, internal oscillator, timer sleep mode) and a circuit that will give a really high current pulse for only a few milliseconds with a very low duty cycle.

 

Look down the aisles in some supermarkets - they have things like that flashing visible red LEDs to draw attention to some display or other - it blinks every few seconds. But they use something like a 555 timer - way too much power for something that needs to be sealed and kept alive for months.

 

Just thought of another idea. Ditch the solar panel entirely - use a lithium battery like the BR2032 (or a pair for 6 volts).

 

Use a phototransistor to hold one of the microcontroller pins low when it's light. When it gets dark, the transistor opens up, lets the pin voltage rise, and trigger a "wake up from sleep" interrupt.

 

Then the microcontroller just pulses the infrared LED for a few milliseconds every few seconds, until it sees the "sleep" pin stay low during the LED off cycle - easy to write in the software - and it goes back to sleep until after it gets dark again.

 

(been reading some application notes since last night)

 

Getting some ideas for a little bitty circuit board that might be fairly economical for people to assemble, or even get a batch of them robotically assembled and tested (probably would have to sell about 200 to break even on the tooling costs). Might cost as little as $10 or so if enough were built.

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