Picture of The Raven, high-pitched torture
This is a little device that I designed for the simple purpose of being discreetly annoying. It waits for a predetermined amount of time, and then it starts emitting high-pitched beeps. I have programmed mine to take advantage of an interesting property of sound. That is, in general most people above the age of 25-30 can't hear very high-pitched tones (say, 17 KHz for instance). This means if you were to (hypothetically of course) place it in a classroom, it would start bugging the heck out of the students while the teacher/professor will (most likely) be completely unaware of the source of the disturbance.
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Step 1: Parts

Not all of the parts I used here are necessarily required. For example, you could use a resonator instead of a crystal, or hypothetically neither. But I won't be going into detail about alterations, if you change something I'll assume you know what your doing. If you don't know what you are doing, you might want to stick to what I've outlined here until you are a little more comfortable with AVR's.

In this project I used an ATtiny25 microcontroller, a handy little chip. I picked this one for this project because it's small and has 2 timers, which will make the programming easy. In order to complete this project you'll need a programmer, there are lots of methods on the internet for programming AVR's (look up "AVR programming" on instructables or google). I personally use the USBtinyISP that Ladyada sells.

Except for the AVR you can proabaly scalvange most of this stuff from old electronics. I needed to make an order to Digi-Key anyway, so I just got this stuff there.

What you need:
*I used a 3.6 V lithium battery, you can use something else, just as long as the voltage is between 3 and 5.5 volts (the weaker the battery, the more quiet the speaker will be).
**You don't need the IC socket, but it will make it very difficult to reprogram the AVR afterwards if you don't use one.
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vitell4 years ago
What's the battery life likely to be?
codongolev4 years ago
why did you use a crystal?
J-Five5 years ago
Quoth the raven NEVER MORE!!!
and my soal from the shadow that lies floating on the floor shall be lifted, NEVERMORE!!!
Poe lived between 1809 to 1849 for that time period he was old.
Yep, but he wrote dam well!
geeklord6 years ago
Could someone make a circuit without out an AVR?
awang8 geeklord6 years ago
You might be able to use a 555 timer chip... I'm not sure.
bman22 awang86 years ago
there was annother device similar to this on instructables, i think the author called it the annoy-a-thing. it uses a 555 cmos timer.
awang8 bman226 years ago
Yes, it is called the Annoy-a-Thing, but that emits a regular beep while this one emits a high-pitched kids-and-dog's-only beep.
if you used 2 555 timers you could beep at high pitch
a totally far stretched idea that might work would be to use a chain of relays with some sort of delay in between them, and resistors to route different voltages into the speaker... this would actually be more useful in creating a melody player... and its probably gonna be kind of big...
animaster5 years ago
can i use an Attiny 13?
Hungry_Myst (author)  animaster5 years ago
Yes, but you will need to modify the code as, to my knowledge, the Attiny 13 only has 1 hardware timer (where the Attiny 25 has 2).
bman226 years ago
i tried this using a tiny2313 i had lying around, besides the fact that the code was a bit to complicated for what i was trying to, i found the tiny2313's internal oscillator didn't seem right or something. Instead of doing the 17khz i jumped straight to telling it to do 20khz, having read that that is the upper bound of the human ear, and that the average adult couldn't hear it. Well, either the oscillator was off, or the 20khz was the upper bound of the adult ear. i had to set it to about 35khz to get it high enough. I actually put mine in a remote control, and used a uni-directional whistle chip instead of the usual piezo speaker. Now i can point it at people and drive them nuts!
sotsirh1946 years ago
What would be an example of code just to make a 38Khz square signal and nothing else with a 1Mhz internal timer. I don't quite understand the code above.
Hungry_Myst (author)  sotsirh1946 years ago
>Here< is a very comprehensive guide to AVR timers that I found extremely helpful.
Wesley6666 years ago
Would it be possible to use an oscillator instead of a crystal?
Hungry_Myst (author)  Wesley6666 years ago
Yes, tough you would need to use different settings for the fuse bits, and if the frequency was different you might need to modify the source code a bit. Depending on what your doing, you might not need either. I used a crystal because I wanted really precise timing over long periods of time.
OK thanks
DaNerd116 years ago
whats this mosquitoe thing?
Mosquito is a device that can be installed in public spaces where young people hang out and generally harass/irritate residents. It might be on top of a lamppost for example. Only kids can hear the noise (as explained below) so they generally disperse. Personally I think it's brrrrilliant! Have to disagree with Croistoir as no-one is forcing anyone - kids can freely move away, and it causes no damage so I think torture is a strong word. I would love one of these as the kids in my street are always damaging property and climbing on my shed! I know not all kids are bad but let them hang out in the park or in their own gardens, not mine.
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ok, lets have a scenario here, there are a bunch of teens in your front yard destroying it, sitting in the bushes, kicking up the grass and the flowers because you live in a crummy area. This happens a few times every week and you are very angry, you have tried calling the police but they dont do anything, they just come over and tell the kids to leave and go back to eating their doughnuts (sp?) What do you do? hmm, the mosquitoe sounds like a great idea now eh?
Hungry_Myst (author)  DaNerd116 years ago
Unless you, or any of your neighbors have kids or are younger then 30 or so (the range of people who can hear it is very erratic), or if they have pets (especially dogs). I would liken this to putting a blow-horn in your front yard. Great if you can't hear it, but you have to take the people your living around into consideration. There are adults who can hear this thing, just like there are plenty of kids/teens who can't (one of my roommates last year can't hear it). There are better ways to solve this problem.
put a remote switch on it. problem solved. along come the kids, on goes the mosquitoe.
well, from that scenario, tell me a better way to solve it.
Hungry_Myst (author)  DaNerd116 years ago
I didn't say I have a solution, you'll just have to be creative. But you also need to take into account all of the people who might be affected by what you do.
well if u cant come up with a solution then i geuss there is no other one, eh?
Hungry_Myst (author)  DaNerd116 years ago
That logic doesn't work. Just because you can't come up with a better idea doesn't mean there isn't one. There are plenty of solutions to this problem; but here isn't the place to discuss them. I'm simply saying that this isn't a solution. What if your neighbors have kids/teens? Something like this could easily give them headaches/migraines, and would likely keep them up at night. Imagine if your neighbor set up something like this and you could hear it. What if the people you were trying to discourage got ticked off at your tactics and decided to trash your property all the more? This is meant to keep kids from loitering somewhere, not to ward them off completely. What if they used earplugs? In any case, here isn't a good place for a debate, so this will be my last comment on the matter.
fine, and also, have u ever heard those mosquitoe ringtones and stuff, earplugs wouldnt do anything, and thats a ringtone, whos point was i just proving?
Speaking as a teen myself, I believe that the mosquitoe is a great idea, so long as it is placed only in 'hot'spots. In a back alley, for instance. Also, the mosquitoe can be tweaked so that it emits differant wavelengths, so it become audible only after yours ears have become accostomed to it, so say 5 minutes. And besides, kids have already turned the mosquitoe to theur advanntage. Some cellphones now have a mosquitoe ringtone. Only kids can hear it, so it would be perfect for class. The teacher wouldn't know the heck is going on, while the kids are busrting them selves try to hold laughter in!
hcold joechump6 years ago
A public place is for everyone, not just those you don't like the look of.
DaNerd11 hcold6 years ago
but they shouldnt have the right to be in a public place if they are terrorizing the people/animals/property in the public place.
hcold DaNerd116 years ago
Terrorising is a strong word, but, this is, as is common, as case of a few bad eggs among the many okay eggs. Punishing everyone for what the few do. It's also discriminatory towards age groups, which is a human right (that is, not to be discriminated on via age).
DaNerd11 hcold6 years ago
well, kinda got a point...... damn... hate it when i lose.....
Oh, now that's a great idea. We have some.. youth... who have started hanging out on the corner. They're not from this neighborhood, we think they're casing it for the chance to rob someone. Make it a little harder for them to stay. I'd like to build a thingum that has an EMP triggered by high decibel levels. Use the magnetron from a microwave, aim it at the corner, and when the punks come driving through at 2am with their crappy music blaring, ZAP!! muhahaha I'm not used to working with high voltage so I'm a bit chicken to put one together, but the basics (not including the decibel meter alteration) are in one of the Evil Genius Electronics books. Anyone out there do it, please shoot me an email so I can add you to my "god" list. Make sure you get some video.
im not saying stuff that you could possibly might be able to geusstimate about, if theyre tearing up ur lawn, thats a good time to use it, not if u SUSPECT that they MIGHT rob a house because they are STANDING on the street, who knows, maybe they all just moved here?
Well we have seen them using binoculars to look in people's windows, I think that's a good enough reason to distrust them and want them to go away. They're not dressed as if they live in this neighborhood, but rather they are walking/biking from several blocks away. And I have seen them lounging around with their homies at those houses, so... my suspicions are pretty reasonable, really.
I will add that when they look in MY windows with binoculars they are likely to see me looking back at them with my spotting scope. ha ha!
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