Introduction: Coin Slot Detector

Picture of Coin Slot Detector

by: amy khoshbin
her website:

when your coin slot is exposed, this wearable hip-pack vibrates that area to make you aware of it. you decide to cover up, or let it all hang out.

the coin slot detector is a simple way to tackle the complicated modern problem low-rise jeans can cause. with this hip pack, now your coin slot itself is given the sensory power to alert you as to when it's exposed. both you and your coin slot decide what's next. 

tech summary: using a Lilypad Arduino, vibrating motor, and a photoresistor (measures the amount of light in your coin slot), you will make a wearable apparatus. when the photoresistor/your coin slot is covered, the hip-pack is at rest, when it/your coin slot is exposed, this triggers the vibrating motor to start vibrating & let the user know.

Step 1: Ingredients

Picture of Ingredients

get your ingredients together!

for this project you'll need:
-11.5 x 14.5 in fabric
-conductive thread
-lilypad arduino
-vibrating motor
-1N4004 diode
-photoresistor (sometimes called photo cell)
-1.5 to 5 V step-up battery pack
-wire cutters
-snap tool
-suspender clips
-plastic tubing

for protoyping (not pictured):
-breadboard (you can buy this at Radio Shack)
-Arduino Diecimila
-USB cable
-alligator clips (also buy these at Radio Shack)
-USB to Serial Converter
-female headers

Step 2: Prototype!

Picture of Prototype!

1. lay out the breadboard & your Diecimila Arduino.
2. connect wires to the breadboard- one wire into the blue rail for ground, and one into the red rail for power. attach the power wire to the 5V input on the Diecimila Arduino and the ground wire to the Gnd input on the Diecimila Arduino.
2. connect a 10Kohm resistor from the ground rail to the center of your breadboard on the same line. then connect a wire in the hole next to it to the analog pin 0 on your Arduino.
3. connect a wire from the power rail to the center of the breadboard.
4. solder the photoresistor's leads to longer wires to connect to the breadboard (about 4-5 inches).
5. connect the photoresistor to ground in the breadboard by putting one wire next to the wire going to analog pin 0. then connect the other wire to power by putting it in the hole next to the power wire you connected in step 3.
5. connect a wire from the breadboard to digital pin 9 on the Arduino.
6. then connect a 1N4004 diode in the hole next to it, and put it so that the ground side (the side with the grey stripe) is facing away from that wire.
7. solder your vibrating motor's leads to longer wires for prototyping.
8. connect one of the vibrating motor's wires to the hole next to the diode. connect the other vibrating motor lead to the ground rail.
9. attach Arduino to computer via USB cable to power it.
10. write the code in the following slide into the Arduino 0012 programming environment.

Step 3: Program in Arduino 0012

open up Arduino 0012 on your computer. copy and paste the following code into your program window...then press the Verify button to make sure it works. Finally, click the Upload to Board button, to upload it to the Arduino to run. Once the program is uploaded, click the Serial Monitor button to see the values changing as you cover and uncover the photoresistor. When the values go above 500, the vibrating motor will vibrate!

/*Coin Slot Detector
by Amy Khoshbin

int photoPin = 0; // Analog input pin that the photo resistor is attached to
int photoValue = 0; // value read from the photoresistor
int vibPin = 9;
boolean isVibrating = false;

void setup() {
// initialize serial communications at 9600 bps:
pinMode(vibPin, OUTPUT);

void loop() {
photoValue = analogRead(photoPin); // read the pot value
Serial.println(photoValue); // print the pot value back to the debugger pane


delay(10); // wait 10 milliseconds before the next loop

void vibrate(){
//change the values greater than and less than to fit the sensitivity of the photoresistors you use

if(photoValue > 500 && isVibrating == false){
digitalWrite(vibPin, HIGH);
isVibrating = true;

if(photoValue < 500 && isVibrating == true) {
digitalWrite(vibPin, LOW);
isVibrating = false;


Step 4: If Working, Program the Lilypad Arduino

Picture of If Working, Program the Lilypad Arduino

if your program runs, and you're getting the photoresistor to get values into the Arduino and vibrate the vibrating motor, then you're ready to move onto the Lilypad Arduino. To program this microcontroller, you need to use an USB to Serial converter.

Since the Lilypad doesn't have headers soldered to them for easy prototyping or programming, I recommend using alligator clips.

First get female headers, then cut 4 off of the strip, and solders wires to each lead. Connect the female headers to the Gnd/RX/TX/Power headers on the Lilypad.

Then cut another 4 female headers and solder them to the USB to Serial Converter in the Gnd/RX/TX/Power holes. Attach the wires from the headers on the Lilypad Arduino to the USB to Serial Converter headers.

Attach the USB to Serial Converter to the computer via a USB cable. In the Arduino programming environment, go to the Tools menu, go to Board, and set it to Lilypad Arduino & set your Serial Port to the top one on the list. Then press the Upload to Board button in the Arduino programming environment, then press the Reset button on the Lilypad Arduino, and watch the program upload.

Once uploaded, we can start making the Coin Slot Detector!

Step 5: Cut Fabric

Picture of Cut Fabric

cut your fabric to 11.25" x 14.25".

Step 6: Pin & Sew Fabric Edges

Picture of Pin &amp; Sew Fabric Edges

picture 1:
-orient fabric where 11.25" is horizontal, and 14.25" side is vertical.
-pin top and bottom edges of fabric by rolling the edge once, then again, and pin them down.
-sew top & bottom edges first.
-then pin right and left edges of fabric.
-sew right & left edges of fabric.
-fold fabric horizontally.

picture 2:
-once right edges are sewn, fold fabric horizontally.
-sew the top 4 inches of the right edges together.

picture 3:
-then roll the top edge of the fabric, pin it down.
-sew the top edge.

picture 4:
the fabric piece is secured on the top half, but can be opened on the bottom half.

(in the images below, the pins are pinned vertically, but as i learned after taking this photo, pin them horizontally, so you can sew over them without them getting in your way!)

Step 7: Snap the Edges

Picture of Snap the Edges

using the snap tool, snap the top edges, .25" from the left & right-hand folds. also snap the bottom edge, .25" from the left & right-hand folds.

Step 8: Sew Battery Pack

Picture of Sew Battery Pack

sew battery pack 1" from left edge on fabric. secure it with thread in two holes on plastic.

Step 9: Sew Lilypad Arduino

Picture of Sew Lilypad Arduino

sew Lilypad Arduino in place 1.25" away from battery pack wire. sew Lilypad in for security with non-conductive thread first.

Step 10: Cut Plastic Tubing

Picture of Cut Plastic Tubing

you can buy this plastic tubing at a hardware store or plastic shop.
measure .5" from edge and cut plastic with a bandsaw or hand saw. sand with sandpaper to get rid of rough edges.

Step 11: Put Vibrating Motor in Tube

Picture of Put Vibrating Motor in Tube

see image below.

Step 12: Motorhead-ers

Picture of Motorhead-ers

attach conductive thread to each lead of motor by wrapping them. leave about 5 inches of thread hanging on each lead. secure with fabric/hot glue.

Step 13: Sew Motor Into Place

Picture of Sew Motor Into Place

sew motor in place on fabric first to secure- .25" from battery wire & Lilypad Arduino.
sew left lead of motor to ground of Lilypad with the conductive thread attached to the motor's lead.

Step 14: Bend Diode Legs to Create Hooks

Picture of Bend Diode Legs to Create Hooks

bend diode legs to create hooks to sew to.
place diode .20" from battery pack, motor, and Lilypad Arduino.

Step 15: Sew Diode Into Place

Picture of Sew Diode Into Place

-sew power lead of diode to Lilypad Arduino pin 9 with conductive thread.
-sew ground lead of diode to left lead of motor with conductive thread.

Step 16: Connect Headers to Power/ground

Picture of Connect Headers to Power/ground

-wrap conductive thread around each right-angle male header. one for power, the other for ground.
-secure with fabric/hot glue

Step 17: Sew Headers to Power/ground

Picture of Sew Headers to Power/ground

-sew lead that connects to the battery pack's ground to the Lilypad Arduino's ground. same for power. -make sure not to cross paths!!

Step 18: Sew the Resistor

Picture of Sew the Resistor

-bend leads of resistor to make hooks to sew to.
-sew left lead of resistor with conductive thread to analog pin 0 of the Lilypad.
-sew right lead of resistor to ground of Lilypad.
-make sure not to cross paths!!

Step 19: Sew Clips in Place

Picture of Sew Clips in Place

-fold fabric in half vertically.
-then sew suspender clips into place on back of folded fabric 1/8" from left & right edges of fabric at top of fold.

Step 20: Solder Photoresistor to Wire

Picture of Solder Photoresistor to Wire

-solder each lead of photoresistor to wire 4 inches long.
-solder this wire to wire wrap that is 5 inches long.
-twist wire together.

Step 21: Sew Photoresistor to Fabric

Picture of Sew Photoresistor to Fabric

-sew photoresistor to back of fabric: 1.5" from clips at each edge. 1.25" from top of fabric.
-leave all 5" of wire to be able to bend and fold.

Step 22: Photoresistor Leads Sewn

Picture of Photoresistor Leads Sewn

-sew leads apart, so as not to short.
-insert wire wrap into the fabric to connect with the rest of the circuit.
-sew right lead of photoresistor to analog pin 0 on the Lilypad Arduino.
-sew left lead of photoresistor to power on the Lilypad Arduino.

Step 23: Sew Wire Wrap Into Place

Picture of Sew Wire Wrap Into Place

-on the inside on the back flap of fabric, the wire wrap from the photoresistor's leads will be loose. you need to sew these into place with non-conductive thread. they will be leading from the photoresistor's leads to the power of the Lilypad Arduino and analog pin 0 on the Lilypad.

Step 24: Wearing the Pack on Yr Pants!

Picture of Wearing the Pack on Yr Pants!


when coin slot is exposed, photo resistor is exposed and triggers vibrating motor to vibrate!


Ecila28 (author)2015-11-13

hi your project is great and awesome and totally cool

can i use it for my school project?

mark.diaz.58118 (author)2015-04-22

so funny! great project!!

grannyjones (author)2015-01-28

My brother has a bud vase. Or maybe that should be butt vase.

ecki242 (author)2013-07-17

First: Thumbs up, cool project. :)
To add the german version: "Maurer Dekolleté", literally translated as "bricklayers décolletage"....

nervouswreck (author)2008-10-31

Hi Amy, Over here in england we call it A Bricklayers Arse, Or when you spot one We ask politly "Can i park my bicycle"

bmlbytes (author)nervouswreck2008-10-31

We call it a plumber's crack (Mid-Northern USA), probably for similar reasons.

smogit (author)bmlbytes2008-11-03

Not sure what part of England you come from, but in my part we call it builders bum, so much more polite...

Callum Snowden (author)smogit2010-12-04

Yeah, sounds about right for yourkshire people.. :)

Spannerz (author)Callum Snowden2011-01-02

It's called Plumber's Crack here in Australia too...
Just goes to show the world is being Americanised - in a good way, of course ;D

Nhuun (author)Spannerz2011-01-23

We call it a plumber's crack (or just plumber) here in Iceland too ;D

nervouswreck (author)Nhuun2011-01-25

Hi Again guys & gal's, Just got in from work and watching a cooking competition, Theres a guy with 2 bicycle parking placesshowing above his jeans, The commentator said "I thought you said your a cook not a plumber"

sometimes in america we say "crack attack!"

Or we might say the moon is awfully bright tonight.

ilpug (author)MadCobbler2011-08-17

or "say no to crack"

ahuerta (author)ilpug2011-09-18

Even "crack kills" works.

eternalwind (author)ahuerta2012-07-08

Me too!!! Don't do crack! (:

sneak right up behind his back,
and strike match
and drop the burning sulfur right between their cheeks!

The Crack Is Back - Hehe xD

pilgrimboz (author)Spannerz2011-10-22

by speaking ENGLISH?? :)

GyroGearLoose47 (author)2012-01-29

This is a totally funny project. I can not comment on the electronics as I am old schooled in electronics. Your photos are consistently excelent. I read about half the comments and others appreciate your efforts, as do I. If your not a Tech or EE, I would be surprised. Please give us more when you can! Thanks.

tuttle1970 (author)2012-01-13

Southern saying..... Crack Kills

techboy411 (author)2011-11-28

COOL. so silly!!!LOL

busterbuster18724 (author)2011-10-26

we call it in nz builders crack

oRelyTo (author)2011-06-06

:P I am confused.

NaturalCrafter (author)2011-04-24

Ha ha! I had to laugh as my friend works on real coin slots. I did not realize what it was till I clicked for a closer look.

guitarmonk15 (author)2010-09-27

Buy (or in true instructabler spirit, make) a belt. Problem solved. That's right, it took me two seconds to outsmart your arduino photoresistor flux capacitor stuff.

hintss (author)guitarmonk152010-12-02

genius! a belt with the arduino photoresistor flux capacitor stuff!

besides, who dosen't like overcomplicating things?

wbothun (author)hintss2011-01-27

Maybe a belt with the photoresister that will engage a belt-tightener

Gamernotnerd (author)2009-08-03

You don't need the Arduino, just wire the photoresistor between the motor and the battery, cheap solution. Or use a MOSFET with a diode to block inductive kickback, if you can be arsed.

Mr.NHRA (author)Gamernotnerd2010-03-26

 The photoresistor will take some of the voltage from the motor and will eventually burn out if you just hook it up in a line. The arduino is the most reliable way to go.

Callum Snowden (author)Mr.NHRA2010-12-04

No, read the post above and that is the easiest and cheapest way, a arduino is OVERKILL for something as simple as that!

markness (author)Callum Snowden2010-12-17

I'd rather just stick with the quarter, but have fun being polite and all.

NachoMahma (author)2008-10-29

. Fantastic job! Great iBle and terrific sense of humor.

hintss (author)NachoMahma2010-12-02

whats your microQR code (atleast it dosen't seem to have the 4th square on it) say?

NachoMahma (author)NachoMahma2010-12-02

. PS: so you don't have to download the pic and then upload it to the site, it says "NachoMahma" :)

AlternateLives (author)2010-10-04

Plumber crack detector. very nice. very nice.

angelabchua (author)2010-09-04

hahahahha man, we need a video of this in action! I know I have been an offender once or twice, or 12 times.

NostalgicStone (author)2010-05-16

 HaHAhahAha Kickass

camscam (author)2008-11-10

That's actually my point. We need a universal cultural ban on butt-cracks I think cute chicks have many better ways to get attention. God forbid if the "coin slot" becomes the new "muffin top"!?

Derin (author)camscam2010-05-16

(removed by the coin slot opener group for being against coin slots)

harrydask88 (author)2010-03-06


dangeross (author)2010-03-04

 lol! this is awesome! ur a genius!

conrad2468 (author)2009-05-31

screw that! go with CRACK SPACKLE! (anyone here watch the man show)

conrad2468 (author)2009-05-31

great idea......but that draws attention to ur arse u dont want that.....cause ppl still might see ur coin slot.

chuckr44 (author)2008-10-29

Did anyone see the "Coin Slot Lotion" skit on Saturday Night Live in 2007? Funny.

chabias (author)chuckr442008-10-30

That was TOO funny!

chuckr44 (author)chabias2008-10-31

Whenever I see a coin slot I want to drop a pencil in there. Is it just me or do others have that urge too? :)

conrad2468 (author)chuckr442009-05-31

ya just want to drop something down there and wait for the sound of it hitting the bottom HA HA HA HA HA

Culturedropout (author)chuckr442008-11-13

I got in _so_ much trouble for doing exactly that in high school about a million years ago... *heh I think it was the screaming that made my "offense" seem so much worse. I figure, if you don't want us enjoying it, don't hang it out there!

About This Instructable




Bio: Amy Khoshbin is a Brooklyn-based artist. She creates hybrid works using performance, video, and interactive media to explore the production and transmission of narratives both ... More »
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