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)

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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.

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Can you use a ATMEGA328P-PU AVR chip instead ??
-chase-3 years ago
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 -

ProTip: bikini with disolvable stitches

Lol, amazing.

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!8 months ago

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


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 ;-)

christzilla3 years ago
Awesome. Just awesome.

Quite. Quite Awesome.

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)
collmanb3 years ago
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...
That's exactly what he did.
rimar20001 year ago
I do not understand how I missed it. I just saw it walking Very original, clever and fun!
Ain't nobody got time for that!!!!
duncan_a2 years ago
For my ex-wife, this idea would have required explosive bolts!!!
de05092 years ago
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?
SBUX3 years ago
this is awesome! but could it be washed? >__<
mogg3 years ago
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
dorchekid103 years ago
is that a guy
I don't understand your circuit at all. There's no A5 on the circuit
the_gella4 years ago
I wanna see someone take it one step further and combine with the secret knock detector for a secret clap off bra.
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
Gene3 years ago
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 Gene3 years ago
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 mklüver3 years ago
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 Gene3 years ago
Hmm... I like the knock code
tkjtkj3 years ago
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?

bird2brain3 years ago
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 Lover3 years ago
what pin do i put the mic on using a regular arduino uno?
ccooper23 years ago
For Narnia...
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.
Ashurii4 years ago
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.
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?!

butterbeans4 years ago
Hilarious. You got my vote.
cvazquez4 years ago
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.
bananaskate4 years ago
oh the hu-mammary
baratacus4 years ago
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)
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