# Recitation 4: Drawing Machines

Disclaimer: This recitation requires you to work with higher voltages. If the circuits are not built properly or in accordance with the provided schematics, there is potential to damage your computer. Therefore, if you choose to use your computer for this recitation, you do so at your own risk. If you do not feel comfortable using your own computer, you can check out an IMA computer for this recitation. In addition, the components in this recitation (the IC and Stepper Motor) will get hot, so do not touch these components when they are powered. Be mindful of this as you complete the exercises below.

# Materials:

For Steps 1 and 2

• 1 * 42STH33-0404AC stepper motor
• 1 * SN754410NE ic chip
• 1 * power jack
• 1 * 12 VDC power supply
• 1 * Arduino kit and its contents

For Step 3

• 2 * Laser-cut short arms
• 2 * Laser-cut long arms
• 1* Laser-cut motor holder
• 2 * 3D printed motor coupling
• 5 * Paper Fasteners
• 1 * Pen that fits the laser-cut mechanisms
• Paper

# Recitation Exercise:

This week, we will be creating drawing machines by using an H-bridge to control stepper motors attached to mechanical arms. Individually complete Step 1 and Step 2 to assemble a circuit using the SN754410NE IC and the pre-installed Arduino Stepper Library.

## Step 1: Build the circuit

Build the following circuit to control the stepper. You can use the stepper_oneRevolution(Arduino>File>Examples>Stepper>stepper_oneRevolution) example code to get your motor to make one revolution. If done correctly, your motor should rotate smoothly.

## Step 2: Control rotation with a potentiometer

Add a potentiometer from your kit to the circuit to allow for analog input. Then, upload the MotorKnob (Arduino>File>Examples>Stepper>MotorKnob) example  to control your motor. Please modify the number of steps within the code to 200, because the 42STH33-0404AC Stepper Motor is a 200 step motor. You can use the function “map()” in order to match the movement of the knob with the rotation of the motor.

## Step 3: Build a Drawing Machine!

Once you have your motor moving via input from a potentiometer, find another person who has also completed Step 2 and pair up with them. Collect the materials needed for Step 3 and combine your parts into a mechanical arm that can hold a marker on paper, as seen in  the picture below. Use your potentiometers to make the motors turn and draw something.

Congratulations, you have just created a drawing machine!

# Documentation:

## Question 1:

What kind of machines would you be interested in building?Add a reflection about the use of actuators, the digital manipulation of art, and the creative process to your blog post.

## Question 2:

Choose an art installation mentioned in the reading ART + Science NOW, Stephen Wilson (Kinetics chapter). Post your thoughts about it and make a comparison with the work you did during this recitation. How do you think that the artist selected those specific actuators for his project?

# Components

### SN754410NE Integrated Circuit (H-Bridge):

Note on how to Identify the front of the IC:

To locate this IC’s front and pinout, look for a dimple or semicircle at its end. This dimple indicates where the front of the IC is. The pin to the left is pin 1, and the diagram below depicts how the other pins are mapped.

SN75440NE ic
Image from upmakerspace.com

### Laser-cut arms:

Laser cut arms: One long (left), the other short (right)

### Paper Fastener:

Image from createandcraft.com