“2-Transistor Ribbon Kit”

Build It - Page 2

First let's make your circuit card. We call this project a “business card kit” because the circuit card is something YOU make - on a business card! If you don't have one of our pre-printed card (you can order them for pocket change at this link), print out the image and glue it to a business card.

Fold the card exactly at the dotted line and close with a piece of tape. Use a big, sharp needle (careful!) to punch holes clear through the card at the center of each black dot.

Next stuff your circuit card with parts.

Find the two transistors, Q1 and Q2. They are different! Look at the parts until you can see the different numbers and their flat spots. Insert them in the card. Check to see that the flat spots match the drawings on the card and BE SURE to match their numbers with the notes on the card. The numbers may not match exactly, but if they don't, they will be close enough that you can figure out which is which (for example, the KSA642G is often labeled just “A642”. Slightly bend the wires (leads) coming out from the transistor body. If you bend them a lot (all the way over) they will become weak and ready to break, so take it easy. Insert the transistor in the card at their marked locations.

Find the resistor and bend its wires so that they go in the holes next to the part marked with the letter “R”.

Find the capacitor and stick its wires into the holes next to the drawing marked with the letter “C”.

Now let's wire up your circuit. Turn the card over.

Twist the wires together as shown on the card. Your twists need to be tight, but don't pull hard enough to rip the wires out of the part. If you have a pair of pliers you may want to twist the wires a bit tighter. When we are building lots of the kits we sometimes make a special jig for twisting wires. We describe the design of this jig in our page for group activities using this kit. If you're just building a couple of these kits you certainly won't need more than your fingers and maybe a little help from a pair or pliers.

After you've twisted the leads, you may choose to solder the connections to make the circuit permanent. You might choose to wait until after you've experimented some before making this “permanent” decision, but most of the other experiments are designed as add-ons to this basic kit, so you won't have to disassemble anything to re-use this circuit in the other projects.

After making the connections, lay the wires down against the card as shown. You're done with the circuit card!

MAKE YOUR RIBBON

Grab a piece of paper or an index card. Take a regular #2 pencil and make a nice dark pencil line from one edge of the paper to the other edge. Be sure to make it dark! Your line can be thick or thin, in any shape you like, but it has to be dark, dark, dark with no open or light bands.

 

CLEAN UP?

We ship our kit with lead-free components. No lead, no lead poisoning, no problem. (NO, your pencil lead is made of carbon graphite, not lead!) If you decide to solder your kit with lead-based solder, now is the time to wash your hands before proceeding.

HOOK UP

Get power. You need at least 1.5V DC (such as a AA, AAA, C or D cell) but the circuit will work with higher voltages or a power supply. The circuit draws very little current and uses almost no power when the speaker isn't sounding, so you don't need a power switch. Hook ground (-) to the wire next to the word “BLACK”. Hook the positive voltage to the wires next to the word “RED”. If you're looking for ideas on where to get power, we describe a bunch of easy ways to hook up a power source over on the group page for this project.

Hook up a speaker. Almost any speaker will do, you can take one out of an old radio or borrow the speaker that's hooked up to your PC's sound card. Your speaker has two terminals, one will connect to the BLACK wire, the other one will connect to the wires next to the word WHITE (it doesn't matter which wires goes to which terminal.

If you are connecting to a speaker from a PC, you may see it has a plug with three terminals. In that case, connect the tip of the plug to the WHITE wire and the ring furthest from the tip to the BLACK wire.

Hook up your ribbon. Connect a jumper clip to one end of the pencil pattern and connect the other end of the jumper clip to the twisted wires next to the word “YELLOW” on the card. Connect another jumper clip (or twist a wire) to the wire next to the word “GREEN”.
LET'S PLAY!

Take the wire from the GREEN point and touch it to to any spot on your pencil drawing. Do you hear the speaker? Move the wire back and forth on the drawing. Does the pitch change? You have built a ribbon controller! Now – let's have some fun! Try to pick out a tune. Try different shapes on your pencil-drawn ribbon. Try sliding the green wire and see what it sounds like.

DEBUGGING?

If your circuit doesn't work, disconnect the power and take a look at your circuit, comparing it to the example picture. Look for loose twists in the wire, unintended wires touching and parts that may be turned around the wrong direction. The transistors are the big question here: they both look the same and they're easy to get switched or turned around: if they're switched or turned around, the circuit just won't work. Check it out!

MORE EXPLAINING

Your pencil makes a conductive path on paper. The resistance of this path is a function of its length, width, and the amount of pencil lead (conductive graphite) you used to draw the ribbon. With a little experimentation you can create a marked scale that will allow you to play songs. Good Vibrations indeed!

>> OTHER EXPERIMENTS!