Introduction: Clap-Off Bra

Picture of Clap-Off Bra

The first time I read about Syrian Lingerie I was quite moved. In the West, we often think of Arab cultures as sexually repressed societies, when - in fact - it turns out that they are clearly leaps and bounds ahead of us in advancements in lingerie technology. Those of us in Western cultures have a thing or two to learn from the Syrians about gaudy electronic lingerie.

Henceforth, it became my mission to fast-forward lingerie technology in the West. I figured the first step in this critical mission was to replicate some of the advancements made in Syria. The article of lingerie that resonated most with my inner sensibilities was the clap-off bra. I immediately resolved to make my own clap-off bra as a springboard into Western lingerie innovation.

On a quiet morning, two years ago, I first set out to make a clap off bra in order introduce it to a much more conservative Western audience. After a long arduous process, I am finally proud present to you a reliably working prototype.

As Seen on Kathie Lee on the Today Show and Hoda on the Tonight Show (27 minutes in).

(note: video mildly NSFW)

Step 1: How NOT to Make a Clap-off Bra.

Picture of How NOT to Make a Clap-off Bra.

Before I make anything, I always look for existing devices that already exist that I can model my project after. I knew clap-off bras clearly already existed somewhere (Syria). So, I looked all over the internet for a clap-off bra so I could see how the Syrians made it work. Despite hours of searching, I couldn't find a single instance of one that wasn't poorly 'shopped in 4chan.

This lack of reference annoyed me, but by no means stopped me from my pursuit. My first though was to use a solenoid. This failed. It got too hot. I immediately wrote off all electromagnetic solutions as potential burn hazards. In retrospect, this was a horrible mistake.

My second thought was to build a tiny spring-loaded quick release mechanism. Of course, making a spring-loaded quick release mechanism is a lot easier to speculate about than actually build. This too ended in disaster. I took some time off from the project.

I then partnered with occasional collaborator Noah Weinstein. We discussed various possibilities for opening the bra and finally decided upon exploding the bra off. Unsurprising, the initial test demonstrated that an exploding button in the front of a bra was going to end in disaster. Yet, this did give us another idea.

We finally decided that we were going to get a large metal button, coat it in nitrocellulose and create a brief incendiary event that would burn the thread away. Hence, when the thread burns away, the button would fall off and the bra would open. Fortunately for whatever poor girl who was going to have to wear this, that approach did not work either. No matter what thread we used, we could never get it to fully incinerate and release the button. This disheartened us and the project was laid to rest yet again.

A year or so passed and I decided to try an idea that Noah and I discussed in passing, but never executed upon. The fourth iteration involved pulling the pin out of the center of a hinge, such that by removing the pin, the bra would separate. We initially didn't want to do this because it would involve using a large motor attached to the bra and this didn't seem very 'classy.' Nonetheless, I figured I would give it a go.

I went out and bought the smallest servo motor I could find and on the first attempt to pull out the pin with the motor, I tore the gears apart and the weak little servo was destroyed. As it turns out, pulling out a pin that runs vertically using lateral force is nearly impossible. Once again, I found myself in overly-complicated mechanical quick release territory. I consulted 'ridiculous clothing' expert Rachel McConnell and she surveyed the situation and surmised that my current approach was pretty hopeless. Normally I would just ignore the project for a few more months, but I was hell bent on just finishing the darned thing.

In talking to Rachel about my long list of failures, I recounted the one idea someone suggested to me early on that I had yet to try. Basically, this involved using a small electromagnet and a strong rare earth magnet and polarizing the electromagnet in such a way that it repels the rare earth magnet. Rachel supposed this would work and I supposed I would give it a try.

So, I went to Radioshack to get some magnet wire to wind an electromagnet. They didn't have any. I went to another they didn't have any either. I went to a third, and they too didn't have any. I headed back and had a moment of inspiration. An electromagnet is basically a coil with some metal in the middle. I just needed to find something with a coil. I tore apart my work station looking for a decent-sized coil of any sort, but to no avail. I finally turned to my office-mate - and all-around good guy - Paul Jehlen, and said to him, "Hey, you wouldn't happen to have any solenoids or big relays or anything with a coil in it?" He produced a defective 5V DPDT relay. This was perfect as it is essentially just an electromagnet that controls a switch.

I carefully cut open the DPDT relay, an exposed the coil. I stuck a rare earth magnet to the end and then powered it up and tried to repel it. This didn't work. The magnet was too strong and it would just reposition itself.

Out of sheer curiosity I checked to see how strong the magnet was with a screwdriver that I had lying around. To my amazement, the electromagnet had a fair amount of pull and was able to lift the screwdriver at 5V. I got to thinking, "I wonder what would happen if I gave the 5V coil a full 9V?" So, I did just this an discovered that the coil didn't heat up as much as I had expected it to and the magnet got significantly stronger. It was now apparent to me that the simple electromagnet inside of a relay powered at 9V was going to get the job done.

Now that we know a bunch of ways not to make one, it is time to actually go ahead and get the job done.

Step 2: Go Get Stuff

Picture of Go Get Stuff

You will need:

A front opening strapless under-wire bra
Black fabric
Small nut and bolt
(x2) Prototype circuit boards
An Arduino (w/ATMEGA168 DIP chip)
28 pin socket
(x2) 22pF capacitors
(x2) 0.1uF capacitors
10uF Capacitor
16mhz crystal
1K resistor
10K resistor
100K resistor
2N3904 NPN transistor
7805 voltage regulator
5V SPST relay
5V DPDT relay
An electret microphone
9V battery connector
A spare USB cable
1" shrink tube
A small grommet
Elastic band
Double stick tape
Quick-setting epoxy
Ribbons and frills
Sewing stuff
Soldering stuff
Tools of various sorts

Step 3: Remove the Clasp

Picture of Remove the Clasp

Cut the clasp off of the bra using cutting pliers (or similar).

Step 4: Prepare the Electromagnet

Picture of Prepare the Electromagnet

Carefully break open the casing for the relay to expose the electromagnet. To avoid damaging the coil, You should start cracking open the case on the side with the switch contact pins. It is okay if the contacts get destroyed, but if you break the coil, then you will need to get a new relay.

Step 5: Prepare the Perf Board

Picture of Prepare the Perf Board

Put your relay into the center of one of the prototype circuit boards and make cut marks around the outline of the relay. These will be used in a moment.

Step 6: Chomp!

Picture of Chomp!

Cut your two prototype circuit boards down to size. To do this I use a paper cutter (or what I like to call a "chomper"). If you don't have a paper cutter, you can also cut them using scissors with slightly less precise results.

One board should have a 1/4" trimmed off of each long end, such that you are a left with a long strip.

The other board should be cut to a small square using the markings you made in the last step.

Step 7: Solder the Circuit

Picture of Solder the Circuit

Put together the circuit using the 28 pin socket in place of the ATMEGA168 chip (for the time being).

Also, don't worry about the electromagnet and electret mic (for now)

Step 8: 4-wire Cable

Picture of 4-wire Cable

Take your USB cable and cut off each end such that you are left with a section of cable roughly 6" to 8" long.

Step 9: Grommet

Picture of Grommet

Cut a small bow-tie shaped section of fabric that will fold over the one of the existing sections of fabric in the front of the bra (the part the clamp was attached to).

In the center of this bow-tie cut a small opening and fasten a grommet.

Step 10: Screw It

Picture of Screw It

Insert the bolt through the grommet from the back towards the front. Fasten it with a nut.

Step 11: Sew

Picture of Sew

Fold the bow-tie over the fabric section in the front of the bra that used to hold one side of the clasp. Sew the fabric down to the bra over the existing fabric. I double-backed the stitch for extra strength.

Step 12: Cut

Picture of Cut

Make sure that the nut and bolt are fastened tight. Using a hacksaw or rotary tool, cut the bolt flush with the nut.

Step 13: Lock It

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Twist of the nut and apply threadlocker to the threading of the bolt. Twist the nut firmly back on.

Step 14: Attach the Cable

Picture of Attach the Cable

Peel back the jacket of the USB cable to expose 4-colored wires.

Attach these wires to the circuit board as follow:

Green - 2N3904 transistor ground
White - Junction of 0.1uF and 10K resistor
Red - SPST 5V relay switch
Black - Circuit ground

...or just look at the schematic again.

Step 15: Program It

Picture of Program It

Download the attached code and upload it to your Arduino board.

Step 16: Transfer

Picture of Transfer

Transfer the ATMEGA168 chip from the Arduino board to the socket on the circuit board.

Step 17: Solder the Small Board

Picture of Solder the Small Board

Solder the electromagnet and electret microphone to the smaller circuit board.

Step 18: Epoxy

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Remove 2" - 3" of jacket from the free end of USB cable. Epoxy the colored wires the small circuit board, such that you still have some wiggle room to work with (i.e. strip and solder) the wires.

Step 19: Solder It Up

Picture of Solder It Up

Solder the wires to the circuit board as follows:

White - Microphone signal
Green - Microphone ground
Red - Electromagnet coil
Black - Electromagnet coil

Step 20: Sew It Down

Picture of Sew It Down

Sew down the small electromagnet board to the fabric in the front of the bra to which the clasp used to attach (and the one not with a nut and bolt attached, obviously).

Step 21: Insulate

Picture of Insulate

Lay down a strip of fabric beneath the long circuit board such that it protrudes 1" past the board on each end. Slide the 1" diameter shrink tubing over the fabric and circuit board. Quickly heat the shrink tubing with a heat gun just long enough for it to tighten around the board.

Step 22: Sew It Up

Picture of Sew It Up

Sew the USB cable along the underside of the bra until you reach the end of the cup. Repeat this stitch a few times so it is nice and strong and then stop sewing.

Step 23: Attach the Circuit

Picture of Attach the Circuit

Sew the circuit board to the top of the back strap of the bra. Attaching it to just the top avoids bunching.

Step 24: Attach the Battery

Picture of Attach the Battery

Sew your elastic straps perpendicular to the bra strap at the top and bottom (such that it will hold the battery). When you are done, slide the 9V battery under the straps.

Step 25: Make a Bow

Picture of Make a Bow

Take your ribbon and make a bow large enough to hide the electromagnet in the front of the bra. If, like me, you don't know how to make a bow, find someone like Scoochmaroo (who "loves making bows more than anything else") to do it for you.

Step 26: Attach the Bow

Picture of Attach the Bow

Attach the bow to the top of the electromagnet by using strong permanent double-sided tape or hot glue.

Step 27: Clasp On. Clap Off

Picture of Clasp On. Clap Off

Plug in the battery. Put the bra on as per normal using the electromagnetic clasp. When you are ready for it to come off, simply clap twice.

If you want to be "modest" about it, you can make your own LED Heart Pasties.

A super-special thanks to Danica Uskert for helping demonstrate the bra.


oldfatnbroke (author)2017-01-19

Pretty much a waste of time! The girl has to know what it does and agrees with the idea so she might as well wear her normal bra. Experience has proven to me that a girl that wants her bra off can remove it much faster than it can fall off even if you used C-4 plastic explosive to open the latch. If said girl is not in agreement it wouldn't matter what you used to open the latch removing the bra would be like removing a bra that was tattooed on!

dorchekid10 (author)2011-09-16

is that a guy

Yorgy (author)dorchekid102016-09-24

Is WHO a guy? The person in the first picture? Because I was wondering the same thing.

Janv133 (author)Yorgy2017-01-13

Look at the movie below. It is the same person and you can see the person has small breasts.

carlosglatzos (author)2015-08-25

This is so funny! Thumbs up. Next build: the force feedback underwear *G*

sapostel (author)2015-08-20

Am I the only one who wonders what happens when the battery dies?

josephkvedas (author)2015-03-08

Can you use a ATMEGA328P-PU AVR chip instead ??

-chase- (author)2011-05-23

That's hallarious - and very inventive.

I remember seeing something like this portrayed in some teen B-Movie made years ago.

lol - things do have a way of making it from the  screen to reality. Even a clap off bra!

I  Love this! - and can think of a new B-Movie and some not so "B" that the plot surrounds this little jewel.

Now I think I'll take this idea and make the clap off Bikini!

That should liven up the beaches here in Florida once again.

thanx for posting this - it turned my day to the postive as I'll be smiling all day as i look at a woman and think of this invention of yours and adapting it to bikini's as i walk theboardwalk at the beach.

;0) definitly a favorite instuctable.

again thanx
- chase -

suomy.nona.14 (author)-chase-2014-10-29

ProTip: bikini with disolvable stitches

EasyHomeConcepts (author)2014-10-19

Lol, amazing.

RobertGoldring (author)2014-08-07

I'm not sure what to think about this, i can think of loads of instances where the clap off bra would be impractical, concerts, birthdays, watching TV and loads more where people are clapping a lot!

guillenxt made it! (author)2014-07-13

Hola amig@s de Instructables, gracias a este post en mi web modifique el proyecto para hacer una lampara que se activa con sonido, espero que les guste.

Gracias Clap-Off Bra

John_the_Builder (author)2014-02-17

Interesting concept. The gears in my brain are turning for other applications this could work with. How about a Pet Door that unlocks when the dog barks to go outside. Hmmm.. I assume it works with any sudden loud noise?
How strong is the magnetic draw? Would a rare earth magnet provide a stronger hold?
PS - Danica looks a lot like someone I dated many years ago. Ahhh, Memories ;-)

christzilla (author)2011-05-22

Awesome. Just awesome.

chatrooms (author)christzilla2014-01-31

Quite. Quite Awesome.

javajunkie1976 (author)2011-12-30

Heaven help the woman who wears this to a show or event where applause is customary!!

tee-hee- hee -lol! I "applaud"your comment

Thanks. I accept your applause. (looks around to see how many bras are falling off)

collmanb (author)2011-05-22

I'd copnsider having a permanent magnet provide the clasp, and only have the electromagnet override it. Then it would rung longer, you'd have even less concerns with overheating, and it would default to "stay-closed" of the battery died, which may or may not be a plus...

Davak72 (author)collmanb2013-09-26

That's exactly what he did.

rimar2000 (author)2013-08-05

I do not understand how I missed it. I just saw it walking Very original, clever and fun!

CrayfishYAY (author)2013-06-18

Ain't nobody got time for that!!!!

rebeccakwalker (author)2013-03-07


duncan_a (author)2012-11-17

For my ex-wife, this idea would have required explosive bolts!!!

de0509 (author)2012-04-14

CORRECTION: Arabs arent totally sexually repressed. they merely reserve all of it for their spouses. Both men and women arent allowed to be intimate with those they are not married to. Leads to a happier marriage without any jealousy etc.

putting that aside, hope i can give a suggestion. not that im good at electronics. actually the pulling of the pin using lateral forces is possible. it merely needs a machine that changes the direction of forces. i present to you the.... pulley!!!
string is horizontal, then it passes the pulley and change direction by 90 degrees.
Just add a bit more cloth below(or above) the hinges to cover the pulley and string. Also would need to take into account ways to put the contraption back together. So maybe dont cover the whole thing. hope it works because with a good gear ratio, you probably could pull it off with a very small DC motor which uses very little voltage. Thinking about durability, the need to washing etc, i guess maybe a bent tube would suffice. the string may get off the pulley tracks right?

SBUX (author)2011-11-06

this is awesome! but could it be washed? >__<

mogg (author)2011-10-01

here are some ideas for clasps that wont use power to keep the bra closed using solenoids. if you make them out of plastic (or metal) you could get them down to about 2cm/ 3/4inch. The first you couldnt hide it behind a bow, but the second can be hidden, and easily reset, you just have to push the pin back in. :) dont have a workshop right now, or is mock something up

Crimson-Deity (author)2011-08-02

I don't understand your circuit at all. There's no A5 on the circuit

the_gella (author)2011-03-22

I wanna see someone take it one step further and combine with the secret knock detector for a secret clap off bra.

static (author)the_gella2011-05-29

Sorry boyfriend, you have to know the secret knock to see MY knockers. Gol darn new technology. Sorry I could resist, I could, but I didn't want to

Gene (author)2011-05-22

Awesome! Though, like all early prototypes, this design could use a lot of refinement, particularly in the miniaturization department. The end goal being something a lady could comfortably wear for an extended amount of time (as pointed out in another comment.) Using lithium coin cell batteries and SMT components would be a start. I have to think that there must be a good reusable release mechanism that doesn't require as bulky of an electromagnet as well. Perhaps the 3 ring release mentioned below.

Maybe I'll get it a go :)

mklüver (author)Gene2011-05-22

I have to say, I don't think this needs to be able to be worn for long term... Picture going to a meeting, and at the end everybody starts clapping.

Gene (author)mklüver2011-05-22

No, you probably wouldn't wear it to the office. But maybe for a night out...

In any case it would be easy to add a arm/disarm switch. Or make it only activate on a knock code.

mklüver (author)Gene2011-05-22

Hmm... I like the knock code

tkjtkj (author)2011-05-22

Clever, yes, but why no schematic or breadboard layout ?? chips are not free, and a misguided connect could blow it...

and when we download the arduino sketch, the filename is vastly different from the filename shown in your instructable... Has it been hacked or what?


bird2brain (author)2011-05-22

Terrific project. I loved that you included so much about the development process and some of the "failures" you had along the way. It's a great way to get people thinking about the alternatives.

I've got one: Since the attachment point should be under a fair amount of tension before release, consider the mechanism used to release malfunctioning parachutes in emergency conditions. It's called a "3 Ring Release" and uses lever action to reduce the force necessary to release the mechanism.

It also has possibilities for the trigger on a trebuchet.

Robot Lover (author)2011-05-19

what pin do i put the mic on using a regular arduino uno?

ccooper2 (author)2011-05-15

For Narnia...

MissMercurial (author)2011-03-26

I read the title and totally thought you were trolling.
Imagine my surprise and amusement when I discovered you weren't!
Adding the BBC article was especially appreciated, btw.

But, from the perspective of a wearer such as myself, I gotta say that it would be 1. functionally insufficient and 2. pretty darn uncomfortable. Why? Well, support largely comes from the band, and your mechanism sort of takes over the band, haha. Though I do like the placement of the USB cable - it's like a quirky ribbon trimming, if you will.
As for comfort, I would think it's self-evident: some people don't even like tags on their clothing, much less batteries taped to their undergarments. Unfortunately, this little number would have to stay permanently in the bedroom "toy box" - wearing it to go out and then revealing the surprise immediately when you get home would be a no go. I have no idea how these could be resolved (although there is that circuit thread stuff, right?), and I'm sure you've considered these factors, but I figured I'd bring it up to add something from the female POV.

Anyway, thumbs up, man.

Ashurii (author)2011-02-25

You might want to remind your date not to take you to the opera or theatre wearing this.
Picture it.
A romantic candle lit dinner. Your wearing your best new tech undies that saved your life before in a freak bra caught in photocopier accident.
You go to the theatre. He looks amazing. The curtain goes down and everyone breaks into applause. A standing ovation.
As your bra flies out of your dress. Clapped off.

MissMercurial (author)Ashurii2011-03-26

Your brain goes off in awesome directions.

Funny as that situation sounds, it would probably never be a problem to consider (at least not with this prototype). Support largely comes from the band, especially for strapless bras, and this one's band is rather bulky - thus defeating its functional purpose.

But if wearing for funsies, who cares about support?!


butterbeans (author)2011-03-22

Hilarious. You got my vote.

cvazquez (author)2011-03-08

You can applaud your girlfriend for her nice lingerie and then it all comes off as some sort thank you for your appreciation. Very funny, and very cool.

bananaskate (author)2011-02-24

oh the hu-mammary

baratacus (author)2011-02-18

wow... very cool. After seeing the pic where you used a threaded stud on a nut I got an idea for a better clasp release that won't come undone if your battery dies and your only power drain when the mechanism isn't opening would be the clap sensor..

I would suggest a small pager motor with a worm gear or a threaded tube on one side and a threaded shaft on the other side. Possibly more compact than the relay and it can not unclasp without spinning the motor. Regardless of how you facilitate it, lingere that flys off on command is just beyond amazing!

(and thank you Danica, you're an eye catcher)

Garasvaldi (author)2011-02-13

looks like much fun at parties, could you make a dress that does that?

mariejessie (author)Garasvaldi2011-02-14

I would think you could make a dress that does this. The easiest way I can think of is to make a babydoll type dress that has the fabric attached to a bra or boustier outfitted similar to this bra. I'd make the skirt portion very gathered with a seam down the middle in front, though the seam shouldn't come all the way up from the hem to the bra portion. For the dress to fall off properly, the opening down the middle front from the bra should be several inches wider than the hips. The fabric used for the bottom half should be fairly light-weight, and the bra/boustier would need to fit snugly.

Garasvaldi (author)mariejessie2011-02-14

@mariejessie good thinking, I would think there would be a market for custom dresses of this type and it sounds like you have the mind to "pull it off" as it were

mariejessie (author)Garasvaldi2011-02-15

Ha, good pun! I certainly could make them...but I've found I just don't like contract or production sewing! Feel free to take the idea and run with it.

Garasvaldi (author)mariejessie2011-02-15

I will have to look into it, I may make a hinged carbon fiber corset(I work in a company that allows me easy access to the material) do you think an electro-magnet would be a good way to go with the clasping?

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Bio: My name is Randy and I am a Community Manager in these here parts. In a previously life I had founded and run the Instructables ... More »
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