Interactive Art: Build Statues That Come Alive When They See You

Wiring the Circuit

Regardless of what your art project looks like, the circuit to control the servo motor will be the same. So we will start with that. Figure 2 shows the circuit you will be building. It is a variation of a very common circuit that engineers design with the 555 chip. This drawing is called a schematic and it is a lot like a road map of your circuit. Wires run wherever there is a line in the schematic, and wires connect where there is a large dot at an intersection. Do not worry about understanding how to build the circuit by just looking at the drawing; we will give you step-by-step instructions.

Figure 2. The schematic for how to wire the servo motors and photoresistors in order to get your art moving.

Figure 3. Some of the parts you will be using. From left to right, the servo motor and plastic servo horn, resistor, two photoresistors (light sensors), two resistors, diode, 555 timer chip, and breadboard.

Figure 4. A completed circuit. This circuit is built on a "mini" breadboard, smaller than the one linked in the materials list.

Note: These instructions will assume you purchased the parts from Jameco Electronics listed in the materials section, and can assemble your circuit exactly as shown in Figure 5. If you have other parts (for example, a different breadboard, or a servo motor with different colored wires), you might not be able to follow these directions exactly. Someone familiar with electronics might be able to help you with your circuit. However, the package of jumper wires you have might have all sorts of different lengths and colors. The colors do not make any difference to the circuit, so you can choose to use colors that make sense to you. For example, using a red wire for positive battery connections and black ones for negative will help you remember which is which. You can also choose wires just for their lengths (keeping them shorter for convenience).

1. Look at your breadboard. Hold it so that the valley in the middle goes up and down. On each side of the valley there are a series of rows that have five holes each. Each of the holes in each one of the rows is connected together, so putting wires in that row is like twisting them all together. You can learn more about breadboards and how they work by looking at the Science Buddies reference How to Use a Breadboard for Electronics and Circuits.
2. Start with the 555 timer chip. Look at the top of the chip (pins pointing away from you). Do you see the small indentation at one end, or a small dot in one corner?
   1. If your chip has the indentation, hold it so that the indentation is up. The upper left corner is called pin 1. Counting down the left side will be pins 1, 2, 3, and 4. Go back up the right side, starting with the lower right corner. The pins on that side (counting from the bottom) are 5, 6, 7, and 8. Pin 1 is opposite 8, 2 is opposite 7, 3 is opposite 6, and 4 is opposite 5. Knowing which pin is which is critical to making your circuit work.
   2. If your chip has a single embossed dot instead of an indentation, that dot is pin 1. Proceed with the pin numbering as is explained in step 2.a.
3. Plug the chip into the breadboard so the pins straddle the gap in the middle, with pins 1 and 8 in row 10, and pins 4 and 5 in row 13. If it does not immediately plug into the board, gently squeeze the pins closer and try again.

Figure 5. Breadboard diagram of how to build the circuit for this interactive art project. Other ways are possible, but you can follow this diagram exactly if you would like. The colors of your jumper wires do not need to match the colors shown in the diagram exactly. However, the colors for the battery pack and servo motor wires mean specific things, so those do matter.

4. Connect your battery pack to the breadboard's buses (the long strips marked by the red and blue lines), but do not put the batteries in the battery pack yet. Connect the red wire to the power bus (red line) and the black wire to the ground bus (blue line).
5. Use a jumper wire to connect the left-side power bus to the right-side power bus.
6. Use a jumper wire to connect the left-side ground bus to the right-side ground bus.
7. Use a jumper wire to connect pin 1 of the 555 chip (row 10, left side) to the ground bus.
8. The capacitor (marked as C1 Figure 2) is a 0.022 μF capacitor, which may be marked as '223'. Connect one lead of the capacitor (C1) to pin 1 of the 555 chip (row 10, left side), and the other lead in a hole for pin 2 of the chip (row 11, left side). It does not matter which lead goes in which hole.
9. Now you will connect the servo motor. If you purchased the servo from Jameco Electronics, the wires should be brown, red, and orange. Brown is the ground wire, red is the power wire, and the remaining orange wire is the signal that controls the servo. Note that other servo motors may have black (ground), red (power), and white (signal) wires instead. The wires have female pins at the end of them, so you can push male jumper wires into them and connect those to the breadboard.
   1. Connect brown lead of the servo to the ground bus.
   2. Connect the orange lead of the servo to pin 3 of the chip (row 12, left side).
   3. Connect the red lead to the power bus.
10. Connect chip pin 4 (row 13, left side) to the power bus (red line).
11. With resistors, it does not matter which end is which. R2 in this circuit is a 2.2kΩ (kilo-ohm) resistor marked with three stripes, red-red-red. Connect one side of R2 to chip pin 5 (row 13, right side) and connect the other end to an empty, unused row (row 25 in Figure 5).
    • Tip: The next two steps will be installing the photoresistor light sensors. In your project, you may want to position the two sensors away from the breadboard, perhaps in a stand where you will place your sculpture. The materials section of the project describes the additional materials you will need to connect the light sensors off the breadboard. You may want to put them directly on the breadboard at first, while you test your circuit, then move them later.
12. R3 is one of the photoresistors that you are using as a light sensor. Insert one side of R3 into the new row where you just connected R2 (row 25 in Figure 5) and the other side into the ground bus.
13. R4 is the other photoresistor. Insert one side of R4 into the new row where you connected R2 and R3 (row 25 in Figure 5), and the other side of R4 into the power bus.
14. R1 is a 3.3MΩ resistor, marked with orange-orange-green stripes. Use R1 to connect chip pins 6 and 7 (rows 11 and 12, right side).
15. D1 is a diode. Diodes work as valves to prevent electricity from flowing back and forth, so it does matter which way you use it. Find the end of D1 that has the black or gray band. Connect that end of D1 to chip pin 6 (row 12, right side).
16. Connect the other end of D1 to chip pin 7 (row 11, right side).
17. R5 is a 110kΩ resistor, marked as brown-brown-yellow. Note: 110kΩ is an unusual size. If you purchased a resistor kit, you might have a 100kΩ resistor brown-black-yellow) or a 120kΩ resistor (brown-red-yellow), and can use that instead. Connect one end of R5 to chip pin 7 (row 11, right side) and the other end to the power bus.
18. Use a jumper wire to connect chip pin 8 (row 10, right side) to the power bus.
19. Use a jumper wire to connect chip pin 2 (row 11, left side) to chip pin 6 (row 12, right side).
20. That is it for wiring! Take a few minutes to check and double-check your work and make sure that your version looks like the one in Figure 5. A single misplaced wire can prevent the entire circuit from working, so be careful!
21. Check to see if any of the wires or resistor/capacitor leads are touching each other. If you find any, bend them a bit to keep them separate.
22. Once you think you have everything right, go ahead and put the batteries in the battery holder. The servo motor should rotate to a position and stay reasonably steady. If you see or smell smoke, immediately disconnect the battery pack and double-check your wiring, because you have a short circuit somewhere.
23. With a bright light above you, use your finger to cast a shadow on the two photoresistors one at a time. As your shadow covers one of the sensors the motor will turn. Cast the shadow over the other one and it turns the other way. If your circuit is working, congratulations; it is time to do the art part of this project. If the circuit is not working, do not worry; the Troubleshooting section will help you find your problem and fix it.

Troubleshooting

You might be asking, "My circuit does not work. What did I do wrong?" Breadboards can be tricky sometimes. Try these fixes:

1. Did you identify pin 1 of the chip correctly and identify the other seven pins? If you hold the chip with the pins facing away from you and the indentation or the small hole at the top, pin 1 will be at the upper left. Count down the left side to get 2, 3, and 4, then starting at the lower right, count up to see 5, 6, 7, and 8. The notch in the chip is facing toward the top of Figure 5. If you put the chip into the breadboard upside-down, the circuit will not work.
2. Are your wires firmly pressed into the breadboard as far as they will go? Check each wire.
3. Is the diode D1 in the right direction? The black or gray band printed on the body will go toward pin 6 of the chip, and the other end goes into pin 7. The circuit will not work if it is the wrong way.
4. Do not confuse the resistors. It matters which is which, so double-check the colored stripes.
5. Remember that each row of holes connects all of the holes on that side of the breadboard together, but not any other rows.

Creating Your Art

With the circuit complete, gather your art materials. Use what you enjoy to sculpt with, whether it is modeling clay, gluing foam shapes together, or making things with craft sticks. Figure 6 shows some materials you might find useful. Small servo motors cannot move very heavy objects, so do not make any part of the sculpture too big or heavy.

Figure 6. Some craft materials you might find useful. Clockwise, starting at the top, the plastic servo horn that will move your sculpture's head, arms, etcetera; paper clips, paper cutouts, pipe cleaners, double-sided foam tape, white (school) glue, rubber cement, and modeling clay. Not shown: clear or masking tape, googly eyes, staples and a stapler, glitter, paint, markers.

• The servo motor itself will need to be stuck into or attached to something. Figure 7 shows the servo stuck into the body of a snowman made of modeling material. The pipe cleaner arms are attached to the servo horn by wrapping them around it, as shown in Figure 7. The snowman's mittens are simply taped on with regular clear tape. Let your imagination take over; what will your sculpture look like? What will you create? Aliens? Monsters? Flowers that sway back and forth?

Figure 7. The pipe cleaner and snowman hands attached to the servo horn and placed on the servo. Attach the hands so that they will be visible from the front.

Figure 8. The whole servo motor and circuit need to be attached to the artwork.

Arrange your sculpture like we did in Figure 9 so that the servo motor is hidden (a magician never reveals his or her secrets!) and the light sensors are facing forward. Point a light source at the sensors and wait until someone walks by. As their shadow crosses one sensor, the servo motor will move one way, then the other, as the shadow continues over the other sensor. Our snowman waves a cheery greeting. What will your sculpture do?

Figure 9. A snowman that waves a happy greeting as you walk by!