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Intro:
This is a very simple and very fun breadboard project.  Once you have everything you need it doesn't take long to assemble. 

Yes, it does work!

I actually made this project once while doing experiments with the Elenco breadboard educational kit.  It is built from "EXPERIMENT #36: DRAWING RESISTORS" page 52 from the kit called "BASIC ELECTRONIC EXPERIMENTS MODEL PK-101".  I changed it up slightly for the purpose of making a smoother tutorial.

Parts Needed:

Power supply (either a 9 volt battery connector and battery or a DC 9 volt power supply and jack with lead wires)
Wires (an assortment of sizes with the ends trimmed bare and tinned would help)
Small Switch (on-off or on-on will work fine)
Speaker 16 Ohm 25 W (Actually just about any little old speaker will work)
Audio Transformer (you can pick one up at Radio Shack for about $3)
Transistor 2N3904
Capacitor Ceramic 0.047uF
Resistor 10K
Resistor 3.3K
Paper (a nice piece of card stock would be nice)
No 2 Pencil

notes:
For so many of my projects I scavenge my parts from old electronics that are worn out.  That saves a tiny fortune on parts but the cost of most of these parts brand new is probably under $10 especially if you order from a place like http://www.taydaelectronics.com
I was disappointed they didn't have the Audio Transformer but I did look it up and found it available at Radio Shack.

Step 1: Connect the Power Supply

Take the two wires from you power supply and push the ends into the "rails" on the side of the breadboard.  I put the positive to the row of holes with the red line and the negative to the row of holes with the blue line.

notes:
You can either use the 9 volt battery option or do like I did and use and old 9 volt power supply I had from something else.

For my breadboard projects I like to use a steady stream of power.  With batteries, a power drop in the battery can affect the results.   Plus I save the batteries for portable projects or when I actually go to build the project into a box.

For my breadboard projects I took a power socket off of some old electronic device and soldered red, black, and white wires onto the leads.  The extra wire is for if I want to utilize the built in switch that is in the jack.  The switch could potentially switch to back-up battery in the event that the unit comes unplugged from the wall unit.


Step 2: Add a Power Switch

Line up the three prongs parallel to the length of the board and carefully slide them into three adjacent holes.

notes:
The switch I use has three prongs and is an on-on switch so that you send a signal from the center prong to either of the outer ones.  In this project I simply use the switch to cut the power to the rest of the circuit.


Step 3: Power to the Switch

Take one of your wires and connect one end from the row of holes along the red line.  Put the other end of the wire into a hole in the row of holes perpendicular to the left prong of the switch.

notes:
Notice the letters and numbers on the breadboard.  The holes can be individually identified by their letter-number coordinates.  All the holes in a number row are connected to each other.  But the holes in letter rows are separate.  By pushing the purple wire into row with the #5 it is thus connected to the left prong of the switch.  On my particular breadboard all the holes next to the red line are connected, known as the red rail; and all the holes next the the blue line are connected, known as the blue rail.  The red and blue rails are usually used for power, red for positive and blue for negative.  The rails on either side of my board are not interconnected so if I want power on the other side I use a wire to jump across.  This project is small so there is no need to do that.

I have several different wires I use for projects.  Most of them are trimmed nicely and then "tinned" with solder.  Then I wrap the ends with electrical tape and put a bit of plastic model kit glue to keep them from unwinding or sliding up when I push my wires.  The other wire I like to use is copper telephone wire.  As you can see by my pictures I like to cut some smaller wires with the ends trimmed so I can quickly make a jump between two holes that are close to each other.

Step 4: Add the Transformer

Add the transformer to the middle of the breadboard.  The front three wires go on one side of the break down the middle and the back two wires go on the other side.

notes:
The transformer has three wires on one side and two on the other side.  If you will notice on the schematic the transformer is next two the speaker.  The two back leads go to the speaker wires.  The side with two wires is known as the secondary side.  The side with three wires is known as the primary side.  On the schematic you can see a P and S accordingly.

Step 5: Connect to the Transformer

Now take a wire and connect from the center prong of the switch to the center wire of the primary side of the transformer.

Step 6: Add the Transistor

With the flat face of the transistor facing the middle of the board slide the three leads of the transistor into three adjacent holes.  The left lead should be in the same number row as the right lead from the transformer.

notes:
Transistors are much like a diode in that they can be used to send current in one direction and not allow it to flow back the other way.  You always need to make sure you put the transistor in the right direction.

Step 7: Add the Capacitor

Now add the capacitor to the board.  The right lead should be in the same numbered row as the left lead of the transformer.

notes:
The ceramic capacitor used here is 0.047uF but is marked with the number code 473.  When you are using many different ceramic capacitors it is important to be able to read and identify them by their markings.  This can get tricky because not all manufacturers mark them the same.  The nice thing about ceramic capacitors is that it doesn't matter which way they face on the board.  With electrolytic capacitors they have to be put on facing a specific direction because they have a plus and minus side.

Step 8: Add the 3.3K Resistor

Next add the 3.3K resistor (Orange, Orange, Red, Gold).  One end goes in the hole in the same number row as the left lead of the capacitor.  The other end goes to a hole in the same number row as the middle lead of the transistor.

Step 9: Add the 10K Resistor

Next add the 10K resistor (Brown, Black, Orange, Gold).  The right lead of the resistor should go into a hole in the same numbered row as the left lead of the capacitor.

Step 10: Connect the Probes

Take the first wire and put one end in the same numbered row as the left lead of the 10K resistor.  The other end of the wire is loose.

Take the second wire and put one end in the same numbered row as the left lead of the transformer.  The other end of the wire is loose.

notes:
The probes are the two longer wires we will use to touch our drawing and make music.

Step 11: Connect the Negative Power Rail

Now make a short jump from the same numbered row as the right lead of the transistor over to a hole in the row along the blue line.

Step 12: Connect the Speaker

The speaker wires go to the same numbered rows as the two leads on the secondary side of the transformer respectively.

Step 13: Test the Circuit

Switch on the power switch by moving it to the left.  Touch the loose ends of the probe wires together.  If everything has a solid connection you should hear a steady high pitched electronic sound from the speaker.

Troubleshooting:
If that doesn't work first make sure your power is connected.  If it still doesn't work you have to go through the board and make sure the wires are making good connections in their holes.

If there is no sound you don't have to keep holding the loose ends of the probes together just find a numbered row that is empty and plug the ends into the same row on the same side of the board.  If a connection is loose somewhere just touching a wire might turn the circuit on and suddenly give you the sound indicating which wire is loose.  If several wires are loose then you will have to secure them before anything will work.

If you think the connections are all solid then make sure the components are lined up with each other properly.  Sometimes you may inadvertently put a wire in the wrong hole thinking it was in line with it's corresponding component.  It is very easy to do with the switch because it may be flush with the board and you can't see which rows the prongs are in.

Step 14: Test Your Drawing Skills

Next take a nice clean thick sheet of paper, a ruler, and a No 2 Pencil and draw a long thin triangle.  The thin solid layer of graphite is what makes the variable resistance connection to make your music.  Be sure to shade in the triangle as solid as you can.  But be careful not to tear the sheet of paper (that is why thicker paper is better).

Step 15: Make Some Noise, Maybe Some Music

Take one probe and touch it to the wide end of the triangle.  Take the other probe and touch it anywhere along the triangle.  When you move the probe it should change the pitch.  The farther the probes are apart the lower the sound should be.

notes:
If you are having trouble getting a consistent sound you may need to go back and make the triangle darker.  Make sure you use a fairly sharp pencil.  It may also help to get the tips of the probes moist.

Making Music:
If you want to make music you can wing it by trying to touch the right probe in positions that sound in tune with your melody.  If you want to be more precise take a pen and make marks above the triangle to indicate the positions of your notes.  Experiment with different shapes and drawings and see how that affects your results.

What's next?
If you want to go on to make this project something more permanent check out my next Instructable!

Also check out my Youtube Demo video to get an idea of where you can go with this project.
i wanna know rating or the value of you transformer <br>
The transformer is a standard audio transformer you can get at Radio Shack. http://www.radioshack.com/product/index.jsp?productId=2103254 <br> <br>You can pick one up for about $3 <br> <br>[Model: EI-19 Catalog #: 273-1380, Frequency response: 300Hz to 10kHz, 1,000-ohm center-tapped primary, 8-ohm secondary, Low-level impedance matching] <br> <br>It works good with any 8-16 ohm speaker.
I made it! It turned out quite well, though I'm having a hard time fixing the pitches to be anything other than screeches.
I'm glad you gave it a try. It's a pretty simple circuit for learning the basics.<br><br>You could experiment using components with different values. It may be that one of your components is bad. When you touch the probes together you should get a solid high pitched tone.
<p>I think I may need a different capacitor; I couldn't find a reliable guide for identifying the ones I had, one guide said that a black-top disc with 47 on it was equivalent to 47nF, so I tried it, but I don't exactly think that was accurate. Thanks for the reply! It was quite fun to build. </p>
<p>is it okay if i will use 324 ohm primary, 8 ohm secondary output transformer and 9 volts or more? i cannot find an audio transformer in our place. Thanks!</p>
It sounds almost the same as the one I used. The link is still active if you are interested&nbsp;<a href="http://www.radioshack.com/product/index.jsp?productId=2103254" rel="nofollow">http://www.radioshack.com/product/index.jsp?productId=2103254</a>
<p>I completed the materials needed and when I started connecting and shorting the probes, no sound would produce and i am planning to change my speaker from 8ohm to 16ohm. What advise could you give for my final exam/project? Thank you.</p>
why do you need an audio transformer? <br> <br>thank you! <br>marC:)
The circuit I built is based on the audio transformer. It is from an old school experimenter kit I built when I was first learning electronics.<br> <br> Read up on audio transformer if you like. They are good for isolating a signal from a circuit which helps with reducing the dreaded ground loop feedback hum.<br> <br> A more modern circuit would use a <strong>555 timer</strong> chip. &nbsp;Depending on where you get your parts this might be cheaper than a transformer and using the chip actually takes up a lot less space. That would be good if you went on to do like I did and build it into a mint tin.<br> <br> Here is an example of a project using the <strong>555 timer</strong> and conductive paint<br> <br> Bare Paint Noise Maker:<br> <a href="https://www.instructables.com/id/Building-a-Noise-Maker-with-Bare-Paint-and-a-555-t/" rel="nofollow">https://www.instructables.com/id/Building-a-Noise-Maker-with-Bare-Paint-and-a-555-t/</a>

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