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Herein, I will outline a few simple tricks to startle, surprise, and maybe even scare someone a bit, using 3 different methods.
#1:  using a recorded voice
#2: using a recorded or LIVE voice, modified,
#3: using the remote method, but nearer.

 
 
 
 

Step 1: Materials and Tools

For the first project, with the recorded voice, I used one of the older, better Radio Shack voice recorders, and build my own Amp around an LM380-8 audio amp. 

Since it didn't need to be REAL loud,  just audible. 

The schematic shows the other parts for the amplifier. 
FYI:  R1  is a 2.2 K ohm resistor.

One also needs the recorder device (some are sold already soldered together, some need to be built  as they are kits),

 One needs a "place" to hide the finished amp and recorder (I put mine inside a base of a music box).

For my project, I decided to go with a plug in power supply for the amp, rather then using the four AA batteries and holder supplied.  So, I found a 6 vdc  wall wart (transformer) and soldered a receptacle to the board, and removed the battery holder and soldered in a plug  to fit the receptacle.  
 

I also used a switch (dpdt, but a spst is fine)

for the other projects I also needed
2 working but not so useful walkie talkies
a CDS cell
and the misc. solder, iron, and screwdrivers, etc.

Caution should be taken when soldering, it burns like hang on the skin, but in the eyes, it'll definitely blind:  wear protection.
 
 
 

Step 2: Putting Together the Recorder Module

What we are shooting for here is to have an innocuous device that either can be "activated" remotely, or by  sensing someone nearby. 

I removed the speaker from the voice recorder (digital, BTW), and wired it (the recorder) directly into the input of the amp.  then wired the output to the speaker.   I had a bit of difficulty as I am much more familiar with the LM386 amp (but not having one handy, I used the LM380-8 instead), so I had to tweak this a bit more then normal to get it to work  well.

Wiring in the CDS cell, in series with the switch should give you some control over the mechanism, so you can turn it off manually.
Once all this is wired together, you can choose a box or "setting" that hides the hardware, after recording your message.

Turn on the switch, and have the CDS cell facing a light source. 

If all has been constructed properly,  someone coming between the light source and the cell, will set off a tremendously funny (just how funny depends on your imagination) pre-recording.

Since it is coming from something the person would never imagine,  it should, at very least, startle.
 
 
 
 
 

Step 3: Prank #2

In my second version of this prank,  I use the same music box, but instead of "just" a recorded voice, I run the output of the amp through an inexpensive voice changer unit I bought for a few bucks, just for this purpose. 
 


I have included a few pictures of what this unit looks like.



 
 
 
 

Step 4: The Best Is Saved for Last :-)

My last version of this prank involves 2 walkie talkies.  I have two ways I could go with this,  I chose the simplest but someone more adventuresome could go the more complex route.

In the simplest form, I removed the voice "recording" device and inserted one half of a walkie talkie pair's guts.  

This allowed me to monitor if someone was near the device from the next room over.  When someone entered the room, I could switch on "my side" i.e. my walkie talkie (using the squelch if one is available to keep it from hissing too loud), and then  speak TO the person.   Your voice (or your modified voice) coming out of an inanimate object is sure to make  even the most suspecting person jump a bit.  

NOW, if you want to make this a bit more effective, albeit a bit more complicated to construct:  you "could" wire the CDS cell across the "send" button of the walkie  talkie guts in the music box (or doll, or where ever you put it), and a third portion of guts "to receive" what you send. What this affords you is that you don't NEED to be in the next room, but you can be up to (the sending distance of the device), many times, as far as 1/2 to 1 mile away.    This definitely has the most "freak  them out" factor of all of these.

I hope you enjoyed this somewhat sketchy outline of my three latest practical jokes.
 
 
 
 
 
 
 
 
 
 
 
 
Nice! I don't have any of these items for this phrank, but I've dona a similar one. (:
Thanks.<br> This one took a bit of doing, and yes, one needs a basic understanding of how the devices work in the first place.
Well... I don't know much about technology, but I think I have enough knowledge to set this one up with the right materials. That's what I like about it. ^ ^
Oh sorry, I just meant that it helps (in case something breaks while you are working with it) to know how it does what it does.<br> <br> I didn't mean to imply you needed to be an endineer or anything :-) &nbsp;
Oh, don't be sorry! I understood exactly what you meant! I'm in middle school, so I'm definitely NOT an engineer. LOL (;
Nor am I one, but I do design things on occasion (for myself and for in here). Nothing elaborate or anything, :-) With over 40 years of tinkering under my belt, I should be able to do something, I guess :-)
That's good to hear. I bet you can make some great things with you practicing design so well and so often. (;
If I had better tools (and more time) I could do a lot better.....we do what we can I guess.
Aww, you make amazing things! I don't know how they could be any better!
Well, thank you for saying so, but some of them could be a lot better. For instance, if I had a heavy wire bending jig, I could have done SO much better with the instructable on my <a href="https://www.instructables.com/id/Ornate-Garden-Fence-segment-to-Cordless-Drill-rack/">rechargeable drill holder. </a>
Good point... I'm not going to lie to you. But everything has it's flaws. We all have our flaws. All that matters is the effort you put in it.... and that you enjoy making it. That's really all that matters. (; <br>
Well, a little more care and time in it would have yielded a better product for sure. :-)
(:
Nice little prank! I'd love to see the remote walkie talkie prank, do you think you'll do it?<br />
Well, I&nbsp;put it together,&nbsp; but I&nbsp;never tested it or used it as of present....only my wife sees the inside of our house (besides me) and so it isn't much good since she knew what I was building :-) <div id="refHTML">&nbsp;</div>
Maybe on your street? Depending on where you live.<br />
Yeah,&nbsp; letting the music box sit out near the trash bin, and getting the trash guys......nah.....I&nbsp;see possible retribution there......Hmmmm, maybe I could put it in a lawn ornament and get the landlord next time he comes over&nbsp; LOL&nbsp;<br /> <div id="refHTML">&nbsp;</div>
Yes! Do it!<br />
Hellllll-o,&nbsp; thish is Carlton yourrrr doorman....<br /> <br /> Oh, wait, that tv show was well before your time (Rhoda a spin off of the Mary Tylor Moore show) <div id="refHTML">&nbsp;</div>
If Wikipedia didn't exist, I'd be lost.<br />
Carlton, as you might now know if you looked it up, was the unseen &quot;doorman&quot;&nbsp;that would use the intercom occasionally on the show....he was always Drunk....
Ahh I&nbsp;wondered why it was written weird. I only looked briefly so I didn't see anything about drunk.<br />
One never saw him either,&nbsp; only heard hish vorcsh&nbsp; LOL

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Bio: I am, most definitely older than 00010101 and to put it simply, still curious about nearly everything :-) I then tend to read and/or experiment ... More »
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