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Pluckers

geocaching beacon help

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I'd love to setup a multi-stage cache where the cache page instructs you to bring a portable FM (commercial band) radio with you on the hunt and use it when you get near the first set of coordinates to hear a morse code message containing the next coordinates.

 

Low-power FM transmitters are cheap and solid-state. http://shop.store.yahoo.com/fmtransmitters/lowpowfmtran.html

Some are used for getting your CD-Walkman to transmit to your car audio system. The range is typically under 150', which would be fine for this purpose. They can be found for under $15, so no need to build unless you are so inclined.

 

Solar power would work for transmitter. Another geocaching ham told me that the fluctuation in power from the panel would only cause a fluctuation in output power of the transmitter. That's fine, just have a warning on the cache page that it is easier to do on bright days. Sufficient power from solar panels can be had for reasonable prices, especially if you plan on placing this thing so that it can probably be retrieved and re-used some day.

 

Now the tricky part where I need help from someone with more electronics knowledge than I. I know that a microprocessor-based chip that generates the beacon message can be had for $8 (http://k1el.tripod.com/kid.html), but I don't think that the fluctuating power from the solar panel can directly power it without screwing up it's internal logic. I think I need to "regulate" this power somehow: if it goes below a certain level, just shut off completely. Anyone know how to do this?

 

I assume it is cheap and easy, since I have really cheap calculators that have integrated solar cells in them, and presumably are driving a microprocessor without messing up it's internal logic.

 

I'd like to keep this thing completely solid-state, i.e. no batteries involved. That way it would be more reliable in the longer term and in colder weather.

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Sounds like a great idea. I would probably use a battery backup, though - with solar panels to charge the battery. That way it should continue to work in the evening, in cloudy weather etc.

 

Surely a tiny transmitter will not take too much power?

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Hi All,

 

This does sound like fun ! As a note to the cache owner, hiding the beacon xmtr at a different location than the cache may eliminate problems with vandalism (of the beacon). ...and the beacon can be placed in a location with good access to sunlight. Just a thought.

 

Safe Caching, Dave, WB2DFC, Akron, Ohio

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Batteries: what about cold/freezing temperatures? It also drives the cost up. The xmtr's I'm talking about are rated about 20mA and the beacon chip is under 5mA. Even in cloudy conditions, 25mA should be easy.

 

Yes, I was thinking of making it a multi-stage, where the first location was where you received coords to the next/final location.

 

If I can build the thing, the fun part will be placing it. Way up in a tree where noone is likely to bother it, or hidden way up on a rock face with only the wire hanging out. The people with the ability to track it down (foxhunting) aren't likely the kind of people to vandalize it.

 

But a low cut-off PS is driving me nuts! I need to learn about op-amps and impedance and stuff. Hurts my brain.

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I've thought of this a few times.

Seems like both times I discussed it with someone, they said an unattended transmission without a license is either illegal or not a good idea.

 

Anyone know if this is the case?

 

Kenneth

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quote:
Originally posted by kennethpruett:

transmission without a license is either illegal or not a good idea.

Kenneth


 

Oh come on, this can't possibly be the case. I'm talking about using the kind of FM transmitter that is sold for use in cars to get your portable CD player's audio into your car stereo. Maximum range is something like 100'. I would be placing this thing 10 times that distance from any trail where any non-cacher is likely to be wandering around with a radio, and 50 times that distance from any road or home.

 

I guess I will just buy the first three items and mess around on a breadboard. That will be fun. I haven't soldered anything since I was a kid! So I'll have to get a breadboard, and an iron/flux/solder... this is how it starts.

 

Another idea, since this is such low power, is to create some sort of stream power device. But that would need periodic maintenance I suppose.

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quote:
Originally posted by Pluckers:

Oh come on, this can't possibly be the case. I'm talking about using the kind of FM transmitter that is sold for use in cars to get your portable CD player's audio into your car stereo.


First I've heard of it too. I don't think you're likely to get in trouble, but the question remains - what is the legalities of unattended operation when using legal but unlicensed low power devices in the broadcast band? Off hand I can’t think of a single advertised use of the device where the owner/operator isn’t within the devices' broadcast range. Do the devices that are sold to advertise houses, etc require a license? That would seem to be the same type of use.

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quote:
Originally posted by GeckoGeek:

I don't think you're likely to get in trouble, but the question remains - what is the legalities of _unattended_ operation when using legal but unlicensed low power devices in the broadcast band?


Does this question really matter? I mean, really, who the hell is going to care, other than some random geocaching/ham-radio/self-appointed-police type nerd? It's way out in the woods.

 

The real remaining question, is, can the K-ID/K1EL chip be solar-powered? Is a simple diode going to do the trick, or perhaps the chip isn't that sensitive to power flucuations anyway?

 

I ordered the FM-XMTR and a solar panel, each under $13. The chip will cost $8. extra parts and weather-proofing and I'll still be under $40. Not bad, if it works icon_wink.gif

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Pluckers,

Where did you order the above mentioned devices? primary interest is the solar panel.

 

Thanks and good luck!

 

Todd - K7PKT

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go to ramseykits. I think they have what your looking for. that is where I have gotten one of my beacons. if you are looking for a 2 meter beacon go to www.neoksimplex.com and check out the ORB beacon. I think it was under 50 bucks. it works great about 36 hour on 2 9 volt batteries

 

Rich and the Lost Yonkers Tribe, Seen My GPS?

145.130 -

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Thanks for the links! so many projects... so little time!

 

Todd - K7PKT

 

Cadence

(OddTodd-K7PKT and CheleBell-XYL)

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quote:
Originally posted by KD5JXU:

go to ramseykits. I think they have what your looking for.


Nope. Not even close: http://www.ramseyelectronics.com/cgi-bin/commerce.exe?keywords=solar&defaction=search

 

quote:
if you are looking for a 2 meter beacon

Nope. Not even close.

 

I did run across this thingie though, which might suit my needs better:

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F011%5F005%5F000%5F000&product%5Fid=276%2D1323

 

Re-programmable by me. Might be less sensitive to power flucuations.

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quote:
Originally posted by Pluckers:

quote:
Originally posted by GeckoGeek:

I don't think you're likely to get in trouble, but the question remains - what is the legalities of _unattended_ operation when using legal but unlicensed low power devices in the broadcast band?


Does this question really matter? I mean, really, who the hell is going to care, other than some random geocaching/ham-radio/self-appointed-police type nerd? It's way out in the woods.


Any time the question of "what's legal" comes up, I'm careful to separate the "legal" from "what you can get away with". The two are very different questions and I don't want any lurkers to get the wrong idea. I can't control what anyone does, but at least everyone goes away making an informed decision and not based on mistaken understanding.

 

I don't have a problem with people doing 65 in a 55 zone (within reason) - as long as they understand what they are doing.

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FWIW, I'm of the uninformed opinion that what you describe is legal, but I don't know for sure. The "unattended" question is a good one, and if I were the one planning to place such a cache, I'd probably pore over 47 CFR §15 and any other portion of the regs my investigation revealed as possibly pertinent.

 

But as the Geek said, it's your call.

 

-----

~ Boyd

N5CTI

 

"Never ask a man where he's from. If he's from Texas, he'll tell ya soon enough. If he ain't, don't embarrass him."

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For the unattended part, I have seen where realtors have used probably similar devices to broadcast info on the houses they are selling. So if they do it I imagine it is legal.

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quote:
Originally posted by Pluckers:

quote:
Originally posted by kennethpruett:

transmission without a license is either illegal or not a good idea.

Kenneth


 

Oh come on, this can't possibly be the case. I'm talking about using the kind of FM transmitter that is sold for use in cars to get your portable CD player's audio into your car stereo. Maximum range is something like 100'. I would be placing this thing 10 times that distance from any trail where any non-cacher is likely to be wandering around with a radio, and 50 times that distance from any road or home.

 

<snip>

 


 

Well, that's why I asked if anyone knew if it was illegal or not.

I was not intending to open a debate on whether you should do it or not.

I have thought about it many times so obviously I don't believe there would be problems with placing one if you can overcome the technical aspects.

I am just one of those who likes to know the "rules" so I know what I'm getting into.

I also try to follow laws as much as possible when I am representing something other than my personal self. If I do something for my company, or in this case representing geocaching, I try to follow things to the letter as my actions can impact others.

 

So as I stated before, anyone know if it is illegal to do an unattended transmission without a license (I don't remember any talk of signal strength, just unattended).

 

Kenneth

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Ooopss...double post...

 

Kenneth

 

[This message was edited by kennethpruett on October 17, 2003 at 03:46 AM.]

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quote:
Originally posted by Pluckers:

Does this question really matter? I mean, really, who the hell is going to care, other than some random geocaching/ham-radio/self-appointed-police type nerd? It's way out in the woods.

 

<snip>

 


 

I care because I'm a geocacher.

Also, you assume all geocaches are way out in the woods.

Here in Atlanta, there are quite a few in urban environments. I'm sure it could become a problem if put in near a populated area. I know I'm stretching it, but this is how things get started....someone puts one way out where no one will ever recieve the signal and then someone puts one near town...then the next one is in town, then a few show up...you get the idea.

 

Kenneth

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quote:
Originally posted by kennethpruett:

(I don't remember any talk of signal strength, just unattended).

 

Kenneth


 

My original post, way back at the top, mentioned "low power" and 150'

 

Good point about what others might do once the precedence is set, but I can only do what's right for myself and let others worry about themselves.

 

I was hoping for a more technical discussion from hammies. icon_frown.gif I guess I will just have to play around on a breadboard and see what happens.

 

[This message was edited by Pluckers on October 17, 2003 at 07:06 AM.]

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quote:
Originally posted by Pluckers:

but I don't think that the fluctuating power from the solar panel can directly power it without screwing up it's internal logic. I think I need to "regulate" this power somehow: if it goes below a certain level, just shut off completely. Anyone know how to do this?


How fancy do you want it to be? As long as the chip starts back up OK when the voltage rises I'd just let it run. You can use a regulator chip to "cap" the voltage. That may help in your design, but that will also throw away some of that valuable solar power.

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be sure to put diodes on the cables. after dark some panels will decharge your batteries

 

quote:
Originally posted by Stu & Sarah:

Sounds like a great idea. I would probably use a battery backup, though - with solar panels to charge the battery. That way it should continue to work in the evening, in cloudy weather etc.

 

Surely a tiny transmitter will not take too much power?


 

Rich and the Lost Yonkers Tribe, Seen My GPS?

145.130 -

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worried about the legal aspects? get a license, simple. Now there is MURS frequencies you may also use or the chicken bands. don't forget there are the remote control devise band. unmanned stations in ham radio must beacon every 10 min. think of it as a repeater.

As far as fm broadcast frequencies go. there are alot of pirate stations out there that the fcc has not messed with.

do it or don't quite worring about that there is always a bit of chance when you are having fun good luck

 

Rich and the Lost Yonkers Tribe, Seen My GPS?

145.130 -

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The situation in the UK seems really bad... Apple's iTrip FM rebroadcaster is banned under the Wireless Telegraphy act. CB can't be keyed automatically. I'm not sure about HAM bands (not being licensed myself), but then it won't be receivable on domestic kit, will it?

 

Shame... I thought this was a nice idea. The only way to check in the US, I guess, is to pore over the regulations.

 

How about an LED up a tree, flashing the morse. That way you have to do one stage at night, then the other in the day! ... except then you need the backup batteries again...

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Do a search for BEAM Bots (Solarbotics.net). I'm sure you can use one of the solar-engine designs. Just replace the motor with your circuit. Also if you wanted to do a voice beacon look into ICISD1420P from Jameco.com I believe it is the same as the RatShk version, just in a 28-pin Dip.

 

You might also look into using a 555-timer to maybe transmit every 5 to 10 min. to conserve power.

 

Hope that helps.

 

Keep us posted on how you do.

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quote:
Originally posted by Pluckers:

quote:
Originally posted by kennethpruett:

(I don't remember any talk of signal strength, just unattended).

 

Kenneth


 

My original post, way back at the top, mentioned "low power" and 150'

 

Good point about what others might do once the precedence is set, but I can only do what's right for myself and let others worry about themselves.

 

I was hoping for a more technical discussion from hammies. icon_frown.gif I guess I will just have to play around on a breadboard and see what happens.

 

[This message was edited by Pluckers on October 17, 2003 at 07:06 AM.]


 

I meant talk with the people I discussed unattended transmission never discussed strength of signal, just that unattended without a license might be illegal.

 

Oh well, I'll just bow out of the conversion and leave y'all to discuss the technical details for doing it, illegal or not.

If anyone ever finds out, please post.

 

Thanks,

Kenneth

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quote:
Originally posted by kennethpruett:

just that unattended without a license might be illegal.

 

Oh well, I'll just bow out of the conversion and leave y'all to discuss the technical details for doing it, illegal or not.

If anyone ever finds out, please post.


I'm with you on this. If the FCC are anything like the UK Radio Bigwigs, then you're asking for serious trouble by contravening radio regulations. Then, if geocachers get tarred with the 'irresponsible' brush, then it can only be a bad thing.

 

I would suggest you find out if it's legal, not if you can 'get away with it' before using an unattended beacon in the name of geocaching.

 

For your own pet project, fine, go ahead, get in trouble; but remember you're representing the geocaching community when you place a cache.

 

As for the 150' argument... it's not really valid. The signal will be capable of being received miles away, given the right antenna! It's still radio spectrum pollution.

 

Cheers,

 

Stu

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quote:
Originally posted by Stu & Sarah:

Then, if geocachers get tarred with the 'irresponsible' brush, then it can only be a bad thing.

 

For your own pet project, fine, go ahead, get in trouble; but remember you're representing the geocaching community when you place a cache.

 

As for the 150' argument... it's not really valid. The signal will be capable of being received miles away, given the right antenna! It's still radio spectrum pollution.

 

Cheers,

 

Stu


 

You know what, you're right. I'm re-thinking this. Maybe the best thing is to construct the site and cache instructions so that the seeker must bring fresh AA's to plug in. I'm picturing a rock wall where the transmitter can be "buried" some distance away to minimize vandalism/theft.

 

You find the batteryholder, plug in the batteries, listen on your FM until you get the message and then unplug. This makes several things go away:

-the possible unattended issue

-solar power tricks

-cold weather

-keeps cost down

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quote:
Originally posted by Pluckers:

quote:
Originally posted by Stu & Sarah:

Then, if geocachers get tarred with the 'irresponsible' brush, then it can only be a bad thing.

 

For your own pet project, fine, go ahead, get in trouble; but remember you're representing the geocaching community when you place a cache.

 

As for the 150' argument... it's not really valid. The signal will be capable of being received miles away, given the right antenna! It's still radio spectrum pollution.

 

Cheers,

 

Stu


 

You know what, you're right. I'm re-thinking this. Maybe the best thing is to construct the site and cache instructions so that the seeker must bring fresh AA's to plug in. I'm picturing a rock wall where the transmitter can be "buried" some distance away to minimize vandalism/theft.

 

You find the batteryholder, plug in the batteries, listen on your FM until you get the message and then unplug. This makes several things go away:

-the possible unattended issue

-solar power tricks

-cold weather

-keeps cost down


 

Now there's a great idea.

Mind if I use it too?

 

Kenneth

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quote:
Originally posted by Pluckers:

You find the batteryholder, plug in the batteries, listen on your FM until you get the message and then unplug.


Good plan!

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quote:
Originally posted by kennethpruett:

Now there's a great idea.

Mind if I use it too?

 

Kenneth


 

Of course not icon_wink.gif

 

I'll followup later with the some resources and the kit I end up with.

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I didn't read all of the responses, but, here's an idea for your voltage regulation. Depending on voltages, you should be able to use a couple capacitors to act as a buffer. Not sure how to compute it, but with a big enough capacitors or several small caps in series, you should be able to get a bit of run time without sun light. As for the shut off part, I'm not familiar with relays, but wouldn't a relay just switch off if the voltage goes below what it's rated at? That would give you an instant off and on mechanism as charge allows.

 

If you would rather use batteries, NiMh batteries or Lithium batteries should work just fine and give you longer run time.

 

Now a suggestion: During one of your stages, when the hunter gets in range of the beacon, put a laminated card with morse code on it. In your CW message you could have the coordinates of the final stage. That would make good use of the CW message being broadcasted.

 

As for the legal part, I'm not a lawyer, but I would go ahead and do it. If it's going to be some where that's not going to cause harmful interference, I don't see any need to worry about. If it's in the middle of no where then I really don 't think the FCC is going to care. Besides, your beacon will be running miliwatts agains the kilowatts or even megawatts a radio station uses.

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I'd love to setup a multi-stage cache where the cache page instructs you to bring a portable FM (commercial band) radio with you on the hunt and use it when you get near the first set of coordinates to hear a morse code message containing the next coordinates.<BR><BR>Low-power FM transmitters are cheap and solid-state. {SNIP}

I have several comments/thoughts, on the original post and some of the replies....

 

If you get an FM transmitter that is part 15 type accepted, like "MR. Microphone" type with less than 15 mW, you are legal to transmit. Even unattended. You simply are prohibited from causing harmful interference to anyone else. The easiest to use would be the type used to send you portable CD player through an FM car radio--they have standard audio inputs.

 

You may not build your own transmitter without a ham license, and then only for the ham bands. I am assuming you focused on the FM broadcast band to make it easy for all geocachers.

 

Rather than using Morse code, which might limit your audience, just use a series of beeps for the numbers. I would also limit the numbers sent, to reduce confusion. Maybe give the degrees and integer minutes, and have the transmitter sent the decimal minutes.

 

The beeps, either simple counting or Morse, would be a fairly simple project for learning about BASICStamp or PIC processors. A simple oscillator keyed by the processor would work fine.

 

You could also use the little chips that come in talking greeting cards, keyed by a simple timer circuit. This way you could either record the beeps as audio, or just use voice. Like this one. I have seen several hams make very cheap "contest keyers" this way.

 

You didn't mention the operating voltage of the chip you were looking at, but there are several regualtor voltages availble in self-contained series regulators. For example, if you need 5 volts you could use a simple 7805 regulator. If the supply voltage drops below about 6 volts the regulated voltage drops with it. You would have to test how your chip behaves with fading voltage. You could put together an undervoltage relay system, but it starts getting complicated really fast. Solar power to charge a battery, and then a series regulator to control the voltage is the normal set up for this type of system.

 

Keeping the duty cycle short is a good way to limit battery drain and reduce the solar array needed. Have a timer set up to transmit the coordinates 3 or 4 times and then turn off the transmitter for 15 minutes. If it only transmitted 30 seconds every 15 minutes, you would save battery life and not make it unreasonable for someone to wait for a couple of cycles to copy the information needed.

 

To summarize;

 

1.If you get one of the part 15, type accepted, FM transmitters you are legal to transmit--even unattended--so long as you don't cause harmful interference. If your neighbors don't complain, you are fine.

 

2. Your options for audio to transmit cache coordinates, and the exact method of operation, are limited only by your imagination.

 

Good luck and 73's de

 

Dave_W6DPS

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Well, did the orginal poster ever get anything on the air? I like the Mr. microphone idea. That with a solor panel and battery backup stuck up in a tree (where it's safe) sounds cool. I had a small fm broadcast band transmiter years ago. I think that it was designed as a cheap mans bug, and I remember that it would run on a 9 volt battery for about three days and had a built in microphone on it. I used it to listen in on my sister's slumber parties that she had with her friends when I was a kid. Something like that with some kind digital voice player would do. Keep us updated. Tim

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Cool alternative to batteries: 1 Farad super capacitors!

 

http://www.allelectronics.com/cgi-bin/cate...-125&type=store

 

They are $1 a piece and they are tiny: just slightly bigger than a pencil eraser. Made from aerogels, the least dense solid substance known to man. These ones are 1 farad, 2.5 volt, so I would order a couple and put them in series to raise the voltage to 5. This will reduce the capacitance by half, so if you still want the full farad, put a string of two more in parallel with those.

 

These capacitors can run an LED for an extremely long time (hours? days?), and they can be charged thousands of times. Now it depends on how much current your circuit would draw - they obviously can't hold as much energy as batteries. Capacitors are tricky - the amount of charge is dependent upon how much voltage you charge it to, and then the amount of charge will determine how long you can run at a certain current draw. And then of course your power going into the circuit is the voltage times the current... aah, me brane 'urts.

 

Anyway just wanted to show off a cool way to run really-low-current devices for a long, long time. I bought a handful of these a while ago and haven't had a chance to tinker with them yet.

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