Introduction: Miniature Beeping Circuit Prank

Picture of Miniature Beeping Circuit Prank

This little device is a fun tool for pranking your friends and coworkers. Every few minutes it emits a brief, high-pitched beep. The beeping gets annoying after awhile, but what is really frustrating is not being able to find it. If you choose a good hiding spot, it can take hours to figure out where it is.

Step 1: Materials

Picture of Materials

Materials:
Jumper Wires
3 Button cell Batteries (I used LR932 cells but other sizes will work)
Printed Circuit Board (RadioShack #276-159)
3-16V Piezo Buzzer (RadioShack #273-074)
100μF 10V Capacitor
555 Timer IC (RadioShack #276-1723)
1kΩ Resistor
4.7MΩ Resistor
Large Paperclip

Tools:
Soldering Iron
Dremel (optional)


Part Substitutions:
The values of the capacitor and resistors are not critical. You can easily replace them with capacitors and resistors of similar values. The only effect will be that it changes the time between beeps. See Step 2 for a better explanation.

The PCB can also be replaced with any other PCB with enough holes to fit all the components.

Step 2: Circuit

Picture of Circuit

The circuit is a basic 555 timer circuit in astable mode. In this configuration the IC sends a brief pulse to the buzzer every few minutes. The values of the resistors and the capacitor determine how often the buzzer will sound and how long each pulse will be. Increasing the value of either the capacitor or the resistor between pins 7 and 8 will increase the amount of time between beeps. Increasing the value of the resistor between pins 6 and 7 will increase the length of each beep. Decreasing these values will have the opposite effect. With the values that I used, it beeps about every 6-7 minutes. (If the capacitor is completely discharged, the first beep may take up to twice as long.)

Step 3: Battery Connector Pins

Picture of Battery Connector Pins

The only parts that you need to make are the battery connector pins. To make these, cut off two pieces of the paper clip that are about an inch long and fold each of them in half. The bent end is where they will contact with the battery. The cut ends will be soldered to the board.

Step 4: Assembly

Picture of Assembly

Then solder all the components onto the board. If you are using the same PCB, you can just copy my layout. If not, just make sure to follow the schematic on Step 2 and check all the pin connections. When soldering the battery connector pins, try to align them so that they are leaning slightly towards each other. This will help make a tight connection with the batteries.

Step 5: Trim the Circuit Board

Picture of Trim the Circuit Board

After soldering everything together, I trimmed off the unused part off the circuit board to make it easier to hide. I used wire cutters to remove the large chunks and a dremmel to trim up to the edge of the circuit. In hindsight, it would probably be a lot easier to cut the board to the needed dimensions before soldering all the parts onto the board. So if you know where all your parts will be, I recommend trying that.

Step 6: Finished Product

Picture of Finished Product

Then just insert the batteries and your annoying beeping prank is ready. Now all you have to do is find a good hiding spot. You can put it inside someone’s computer, tape it to the inside of a drawer, or stick it behind a piece of furniture. Use your imagination. The batteries should last between several hours to several days depending on the size of the battery that you used. But your victim will probably find it before the battery dies depending on how determined/obsessive they are.

Be creative and have fun.

Comments

kevin.longeuay (author)2014-10-30

Great post! I actually have a "nicer" use that I'm to build for... My cousin works with blind kids and they've been looking for a beeping hockey puck so this could be perfect for it! Any recommendation on a capacitor for a one second beep interval? Also, any idea how to ruggedize

Hi Kev, Change up the 4.7M res for a value around 50-100k. THat should do it!

My 9 year old daughter is blind and I'm hoping to figure this little thingy out to put in plastic easter eggs ? I'm also having issues wrapping my head around what combination of materials to use in order to get a 1 or 2 sec interal. If you narrowed it down and figured it out pleeeaaase share the info with me ?

CameronM37 (author)HeatherH1742017-09-28

Totally cool! Yes. The smaller the capacitor, the quicker the interval. I think if you sub a 4.7M for a roughly 68k res it should be much more frequently! Very creative and positive application of this circuit!

CameronM37 (author)CameronM372017-09-28

Not capacitor...resistor

I didn't get around to trying it out but the 555 timer calculator that the author sites below seems to be a good way to figure it out. A 1muF capacitor theoretically has a frequency of 3.5 secs and a 0.2muF has 0.7 seconds, both of which you can find at radioshack. I'd say try both and see which works better

The easiest thing to do is use a 555 timer calculator like this one.
http://web.udl.es/usuaris/p7806757/555-calculadora/555%20Calculator.htm

Perfect! Thank you

DylanH90 (author)2016-10-27

Is there a way that you could significantly increase the volume of the buzzer?

Just use a louder buzzer. But this might require a different battery and potentially a transistor to drive it if it needs more current than this chip can output.

miknight (author)2016-10-12

I built this today, using parts from Radio Shack, but they didn't have the 4.7M Ohm resistor, and he thought it was probably a misprint anyways.. So he sold me a 4.7 K Ohm resistor. It has not chirped at all, not sure if the resistor is the problem, something I did, or what it could be... I tried the batteries in both directions. Nothing.. Anyone here able to help? , maybe do a video on this?

No. 4.7 Mohm was intentional. It is a less common value though. You could also just use a 1 Mohm. It will just change the timing. If you are still having problems after changing the resistor let me know.

Ok, just picked up some new resistors, got the 1Mohm. They are 1/2 watt, just like the 1Kohm . I was told there is 1/4 watt as well, but I didn't see a specification on this, so I stuck with the 1/2 watt. I'm starting on it now.

The wattage rating makes no difference as long as your circuit doesn't exceed the rated value. In this case, you are well below that. So it doesn't matter.

miknight (author)miknight2016-10-15

ok, still not working.. wondering if its my soldering job, or if its perhaps my batteries.. I'm using three Radio Shack 389 which are 1.55V each.??

erjones (author)2016-06-09

Hi. I am a frisbee golfer. I live in Oregon where there is a lot of vegetation and we are always losing our frisbees in the bushes/trees/grass... I would like to make a very small beeper to attach to the center of the disc to help us find it. It would have to be VERY small and flat to not affect the frisbee flight. Ideally the size of a quarter or less and have a little button to turn it off and on. It should beep about every 5 seconds or so. Do you think this is possible?

JeremyR74 (author)2016-05-31

I dont have the spare time to make one of these, can you make one that beeps every three seconds to put on my cat so he cant catch rabbits and squrels

you could try a bell

yoh-there (author)2016-04-24

May I suggest to use a 7555 instead? It will last a lot longer and you might even get away with running the entire thing on 3 volts.

yoh-there (author)yoh-there2016-05-30

Nix that please. A 7555 is using much less energy, but requires higher voltage. I recreated this project using a ATtiny85 that's 99.9% of the time in sleep mode and lasts 100 days on a single 3V CR2032 coin cell. 8 year old son of a friend of mine drove the teacher bonkers but kept his mouth shut!

Fex00 made it! (author)2016-05-17

I did a bit of re-arranging, and managed to super-miniaturize it as well as provide an alternate power source.

Thanks for the guide. Now to surreptitiously "break" every computer in the house.

Tanmay Deuskar (author)2016-04-25

I made this and it is amazing.Though I have one question, how did you calculate the the time gap between each pulse(a beep) and the length of each high signal.I tried checking on the net but couldn't make much of it.

Thanks

JayB107 (author)Tanmay Deuskar2016-05-13

Will you make 10+ plus for me? I don't have the time or materials for this. But I can pay!

Well. This circuit is a 555 timer in astable mode. You can read about this circuit here: https://en.wikipedia.org/wiki/555_timer_IC#Astable

The easiest way to work out the timing of this circuit is to use an online calculator such as this:

http://web.udl.es/usuaris/p7806757/555-calculadora...

or this:

http://www.ohmslawcalculator.com/555-astable-calcu...

or this:

http://www.csgnetwork.com/ne555timer2calc.html

But if you want to get into the actual math of this circuit it gets a little more complicated. A 555 timer is a 3 input comparator circuit with a built int flip flop circuit. When the input at pin 2 is below 1/3 of the supply voltage, then the output is at pin 3 if HIGH and pin 7 is disconnected. When the input at pin 6 is above 2/3 of the supply voltage, the output at pin 3 is LOW and pin 7 is shorted to ground. So if you start with a discharged capacitor, then the output starts LOW. The capacitor charges through the resistors. Then when it's voltage reaches 2/3 of the supply voltage, it switches the output to LOW and 7 is grounded. The capacitor then discharges through the resistor between pin 6 and 7. When the capacitor voltage drops below 1/3 of the supply voltage then the output switches back and the capacitor begins to charge again. This cycle repeats in an infinite loop.

Fex00 (author)2016-03-30

In the interest of excessive miniaturization, would this work with ceramic capacitors, specifically surface-mount? If not, what alternative type of surface-mount capacitors would be suitable?

As long as the they have the same value, the type of capacitor makes no difference. But you will have a hard time finding a ceramic capacitor this big. Instead, you will want to use larger resistors to compensate for the smaller capacitor values.

tokamocha made it! (author)2015-10-30

Finally got around to doing this prank. Thanks for the tutorial.

I put this beeper in the walls of the house, and they couldn't find it for a 5 days. I made sure to use alkaline AA batteries to make it last longer.

I used a 330 mF cap, 2M Ohm R1, and a 560 Ohm R2. It beeps for 0.1 ms every 8 minutes (approx). I found that this combination was the most noticeable, while still having a long enough interval so that it's hard to find.

Only disadvantage is the size, but it's still small enough to fit behind a light switch in the wall.

Thanks again!

spark master (author)tokamocha2016-04-01

use d cells in a wall they last for months, put two sets or more in parallel. The original version of this was called "the tormentor" and the elapse time between beeps was randomized. So you thought you were ready then it didn't then it did then it went faster time, using a nice tough glue inside a desk (I removed drawers), it was never found. Poor nasty Smeagol never could quite figure it out, or find it.

If you are going to torment a supervisor make sure there are no cameras and use ruber gloves.

Awesome

EfeY2 (author)2016-03-19

Is it possible to make this circuit to work not in few minutes but sound commands. For example if my friend coughs then it beeps. If it is possible can you share?

Yes. It is possible to make it react to sound. But people might not hear it if it is beeping at the same time as a loud noise.

tokamocha (author)2015-09-16

Great tut

How long do the batteries last?

What kind of battery and how many should I use so that this buzzer beeps for a week (7 min intervals).

It all depends on the batteries that you use and the exact parts that you build it with. The battery should have a mAh rating. Divide the mAh rating of the battery by the current rating of the Timer IC and that is how many hours it will run for. But in most cases, they will find it long before it runs out of batteries.

Thanks, I added the buzzer mAh to the denominator too. (That's correct, right?)

Also, why did you choose 4.5v, why not use 3v?

The timer IC will be on all the time. The buzzer is almost never on. So it doesn't factor in as much. 4.5V is the lowest voltage the the timer IC will work at. It can't run on 3V

Tanmay Deuskar (author)2015-09-07

Really good prank and also really funny. Though i didn't get the cause of the time gaps between each beeb

Sorry,what i meant by the question was that how does the capacitor determine the time gap between each beep.

Thanks for the quick reply!

If it is constantly beeping, it would be really easy to find. But if it only beeps every few minutes, it is much harder to track down making it even more annoying.

rahulmittal99 (author)2015-03-18

I want to make a device which beep when I press a button, can someone help me how to build up such a device.

Just get a 3 volt piezo buzzer and connect it to a battery with a switch.

lashultz (author)2015-03-05

I am a novice, but this seemed like a do-able project for me. Your instructions were very easy to follow and detailed, so I was very surprised when I couldn't get this to work. For some reason, I keep getting a static/chirping type sound from it, but no beeps. Any idea what could cause this?

Make sure that you are using a piezo buzzer and not a speaker. The beep pulse may also be to short for the buzzer to really sound. Try adjusting the values of the smallest resistor.

It is a piezo buzzer. In fact I used all of the same parts that you described except the largest resistor (10M was the closest I could find). I started with the 1K for the smallest and changed it over to a 22K and still nothing :-/ I've looked over your pictures several times and everything looks right. Just wondering if perhaps there is a common mistake that I'm making or what?

Replace the buzzer with an LED and see if it blinks when it is supposed you. Then check the buzzer with a battery to make sure that that is working.

mykuls made it! (author)2015-02-25

Worked out great. I powered it with a usb cable. Going to plug it into the back of someones computer or tv ;) Used a 1M resistor to decrease time between beeps and a 2.2k to increase length of beep.

Awesome. Thanks for sharing.

simplyelectric (author)2015-02-10

Nice use of the standard astable mode. On a side note I am making around 30 of them for April 1st, parts are ordered now to wait the 2 weeks from china shipping. Only I am using an hour interval for longer run time and to make it harder to find them.

Sounds like fun. Let me know how it turns out.

ethan.bristow (author)2015-01-04

I dont know how to read a circuit diagram well. Where do the - in and + in go?

Here is a tutorial on how to read circuit diagrams.

https://www.instructables.com/id/HOW-TO-READ-CIRCUI...

The + in is the 4.5V supply voltage from the battery.It is connected to the speaker, pin 4, pin 8, and the 4.7Mohm resistor.

The - in is the common ground and is connected to pin 1 and the capacitor.

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Bio: My name is Jason Poel Smith I am a Community Manager here at Instructables. In my free time, I am an Inventor, Maker, Hacker, Tinker ... More »
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