Musical Pencil This circuit takes advantage of the fact that graphite in pencils is a conductor, and people are also conductors. This uses a very small voltage and high resistance so that it s safe. When you simultaneously hold the pencil with one hand, and let the pencil tip and your other hand both touch your drawing, the circuit will activate and a sound will be produced. You can take this project to the next level by making your direct power source be an Arduino instead of a battery pack and then download music code onto the Arduino, so that when the circuit is complete it will make a song instead of a note (the Arduino can be powered by either a laptop or a battery pack). If you play a musical instrument, different notes correspond to different frequencies and depending on the resistance between pins 2 and 7 of the chip, a certain frequency will be outputted. Tutorial modified from http://makezine.com/projects/drawdio musical pencil/
Step 1: Insert 555 chip and some wires, resistors This is a breadboard. Use your breadboard facing you in this orientation shown while following this musical pencil tutorial. We call the gap in the middle of the breadboard the valley. The pins next to the red lines are the (+) Power lines. The pins next to the black lines are the ( ) Ground lines. This is a 555 chip. This chip can output pulses of electricity. The frequency of those pulses can be controlled by changing the values of the resistors and capacitors connected to it. A transistor (described in the next step) amplifies those electrical energy pulses which are then translated to loud, audible sound energy wave pulses via a speaker. Cool Fact: How does a (electro dynamic) speaker translate electrical energy to sound energy? When electricity passes through a wire, this always produces a tiny magnetic field around the wire. When electricity passes through a coiled wire, the magnetic field becomes more concentrated and stronger. A speaker has a coiled wire inside of it, and a permanent magnet also inside of it. As the electrical current increases, the magnetic field increases and attracts the magnet. When the magnet moves, this is mechanical movement and pushes the air molecules beside the magnet very quickly (way faster than your hand can push on air), producing sound waves we can hear. Insert the 555 chip across the valley with the half circle indent facing the top, and connect: a black wire from pin 1 of the chip (immediately the left of the half circle) to the Ground ( ) a red wire from pin 8 of the chip (immediately to the right of the half circle) to (+) a red wire from pin 4 of the chip to (+) a 10 k Ohm resistor (brown black orange) from pin 7 of the chip to (+)
Step 2: Insert transistor + more wires, resistors This is called a (NPN type) transistor. It s shaped like a half moon with a flat side. With the flat side facing you (as shown): Far Left = E = Emitter Middle = B = Base Far Right = C = Collector In this orientation ( flat side facing left ), you could say that: Top = E = Emitter Middle = B = Base Bottom = C = Collector Insert the transistor with flat side facing left above the chip (each leg into a different row), then connect: a red wire from the top leg (Emitter) to VCC (+) a yellow wire from the middle leg (Base) to pin 3 of the chip Connect an 8 Ohm resistor (black grey black) from the bottom leg (Collector) to ( )
Step 3: Insert black capacitor This (black item) is a 100 µf electrolytic capacitor. Capacitors stores voltage and then releases it in pulses, just like your heart does. Electrolytic means it matters what direction it faces. Just like an LED, the + side (longer leg) should face towards the power source (if someone sets up their colour coding nicely, this usually means towards a red wire). Recall this is a (NPN) transistor. In this orientation ( flat side facing left ), you could say that: Top = E = Emitter Middle = B = Base Bottom = C = Collector Connect: the longer leg of the 100 µf electrolytic capacitor (black item) into the same row as the Collector (bottom leg) of the transistor the shorter leg of the 100 µf electrolytic capacitor (black item) to a totally unused row above the transistor.
Step 4: Insert orange capacitor and 10M resistor This (orange item) is a 570 pf capacitor. Both legs are the same length. You can insert it backwards and it will still work. IMPORTANT: IF IT SAYS 104 ON IT, IT S NOT A 570 pf CAPACITOR Connect: an orange 560 picofarad Capacitor from pin 6 of the chip to Ground ( ) a 10 MegaOhm (brown black blue) from pin 6 of the chip to a totally unused row below the chip
Step 5: Insert other orange capacitor This (orange item) is a 0.1 µf (microfarad) capacitor. It looks very similar to the other orange capactor, except it has 104 written on it. Recall that, if the chip s half circle is on the top, then pin 5 is on the bottom right of the chip. Connect the orange 0.1 µf (microfarad) capacitor from pin 5 directly to ( ) View ignoring the other capacitor that was added to the breadboard in the previous step, to make it easier to see where to put the new capacitor: View including the capacitor already on the breadboard:
Step 5.5: Insert grey wire across the chip + LONG wires that will later be attached to pencil Take a grey wire and put one end next to pin 2 and the other next to pin 6 of the chip Take a LOOOONG blue piece of wire (about the length from your fingertips to your elbow) and put it in pin 7. The other end of the wire does not connect to anywhere yet Put a 270k ohm resistor (Red Purple Yellow) from pin 2 to a row below the chip that is totally unused Take another LOOOONG blue piece of wire and put it in the same row as the 270k ohm resistor you just put in (i.e. the row below the chip that was totally unused before)
Step 6: Insert speaker This is a piezoelectric speaker. It makes sound in a different way than the electro dynamic speaker described earlier. Certain materials are said to be piezoelectric, meaning that when electricity goes through them, it puts mechanical pressure on the material. This piezoelectric speaker has a ceramic disk that has mechanical movement in response to electricity. This is a buzzer (shown left). You could use a buzzer instead of a speaker for this project, but if you do remember that buzzers have a long, positive leg and a short, negative leg and the long, positive leg must be inserted facing towards the power source (or towards any red wire if you followed the colour coding in this tutorial). Recall this diagram showing that the shorter leg of the black capacitor was on top. The wires attached to the speaker can be any colour (here they are white). Connect: one end of the speaker to the short leg of the Black Capacitor the other end of the speaker to ground ( )
Step 7: Connect Power The breadboard you are using should have a red (+) line on both sides and a blue or black ( ) on either side as well. First Connect: a LONG red wire (about the length of a finger) from any pin of one (+) line side to any pin in the opposite (+) line a LONG black wire (about the length of a finger) from the any pin of one ( ) line side to any pin in the opposite ( ) line Make sure your battery pack is turned OFF, then Connect: the red wire that s built in as part of your battery pack to a pin in either (+) line the black wire that s built in as part of your battery pack to a pin in either ( ) line Make sure you put it on the opposite side of the breadboard as the battery box s red wire, so they don t accidentally touch (this would cause the battery box to burn out and be useless)
Step 8: Make pencil circuit In the 16th century, large amounts of graphite were discovered in England. People noticed that if you rubbed graphite against paper, it left a mark. The people who discovered graphite thought it was the same material as lead (it s not), and to this day we still call pencil lead lead even though it s actually graphite. Conveniently for us, graphite is also conductive. For this musical pencil project, you must use a pencil that does not have an eraser on the back because erasers are insulators. This is copper tape, which is sticky on one side. Cut about 10 cm of copper tape, and stick about 4 cm of it onto an exposed end of either one of your LOOOONG blue pieces of wire (the end that isn t in your breadboard) Stick the rest of the 10 cm piece onto the half of your pencil that s closest to the writing tip ( example shown left ), so that when you use the pencil, your writing hand will touch the copper. Cut a short 8 cm of copper tape (could even be 10 cm again if it s hard for you to estimate) and stick about 4 cm of it onto an exposed end of either one of your other LOOOONG blue pieces of wire Stick the rest of this copper tape over the back of the pencil, and then cut off any extra so your hand or arm doesn t accidentally touch it when you write
Push a thumb tack into the back of the pencil, overtop of the short strip of copper tape, to ensure there is a solid connection between the graphite and the short copper tape ( example shown left ). Step 9: Activate your pencil! Turn ON your battery pack and start drawing! You must touch the drawing with one hand and the pencil with another to hear sounds. Remember: There must be a continuous path through the graphite drawing between your non writing hand and the pencil tip in order for the circuit to be complete. For example: If your hand touches a drawn smile and your pencil touches an eye, no sound will be made because paper by itself is not conductive. Your drawings will work best if you draw thick lines to ensure there is a connection.
An Extra Challenge: Note: This is an advanced challenge Find a sample musical Arduino code, so then you can take this project to the next level by making your direct power source be an Arduino instead of a battery pack. Download the musical Arduino code onto the Arduino, so that when the circuit is complete it will make a song instead of a note (the Arduino can be powered by either a laptop or a battery pack). You will need to use a 3V Buzzer in series with a 100 ohm (brown black brown) resistor in lieu of your speaker in order to clearly hear the song. To prototype, you should use the guide here (a 100 ohm instead of the 1k ohm stated makes the volume louder we have tested this for safety). If you can get it to work, then put the 3V buzzer in series with a resistor in place of the speaker in your musical pencil circuit. Thanks to Lee s Electronics on Main St in Vancouver for providing our camps with many of the supplies for our electronics activities.