Clap-Off Bra




Introduction: Clap-Off Bra

About: My name is Randy and I am a Community Manager in these here parts. In a previous life I had founded and run the Instructables Design Studio (RIP) @ Autodesk's Pier 9 Technology Center. I'm also the author of t…

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.

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

You will need:

A front opening strapless under-wire bra
Black fabric
Small nut and bolt
(x2) Prototype circuit boards
An Arduino (w/ATMEGA328 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

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

Step 4: 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

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!

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

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

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

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

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

Step 11: 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

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

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

Step 14: 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

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

Step 16: Transfer

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

Step 17: Solder the Small Board

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

Step 18: Epoxy

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

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

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

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

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

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

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

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

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

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.

Did you find this useful, fun, or entertaining?
Follow @madeineuphoria to see my latest projects.

3rd Epilog Challenge

Participated in the
3rd Epilog Challenge

Be the First to Share


    • Rice & Grains Challenge

      Rice & Grains Challenge
    • Lamps Challenge

      Lamps Challenge
    • CNC and 3D Printing Contest

      CNC and 3D Printing Contest



    11 years ago on Introduction

    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 -

    Ricardo Furioso
    Ricardo Furioso

    Reply 1 year ago

    Old ProTip: Dissolvable bikini.


    5 years ago

    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!


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


    7 years ago

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


    7 years ago

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

    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!

    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 ;-)


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


    Reply 9 years ago on Introduction

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


    11 years ago on Introduction

    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...


    9 years ago on Introduction

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