Etch a Sketch Joystick
The Etch A Sketch is a drawing toy with a thick, flat gray screen in a red plastic frame. There are two white knobs on the front of the frame in the lower corners. Twisting the knobs moves a stylus that displaces aluminum powder on the back of the screen, leaving a solid line. - wikipedia
This toy is basically a simple two-axis plotter, so using a few geared DC motors, you can easily add additional functionality using a joystick (or Wii remote) to control it.
Materials:
- Arduino - https://amzn.to/2DLjxR2 (I used a nano instead)
- Breadboard - https://amzn.to/2RYqiSK J
- umper wires - https://amzn.to/2RYqiSK
- Wii Nunchuck: https://amzn.to/2RYqiSK
- Etch A Sketch: https://amzn.to/2RYqiSK
- DC motors: https://amzn.to/2RYqiSK
- H-bridge: https://amzn.to/2RYqiSK
- Some 3D-printed parts
Physical Build
I made a simple frame out of cardboard and hot glue, but I ended up 3D-printing an adapter piece for the motor. Here's how to build it:
- Print two adapter pieces (file is below)
- Fit the motors in place - you may need to use a heat gun or blow drier to help it fit
- Cut and glue pieces of cardboard around the motors to hold them at a 90° angle, make sure they can't move around
- Attach a breadboard, battery holder, and a place for the Wii remote to rest
Downloads
Circuit
Make the circuit as shown above:
- You may want to use a higher voltage battery than shown
- More information about using a Wii remote with Arduino
Code
Upload this code in the Arduino IDE (Wii remote functions from Tod Kurt's library):
#include #if (ARDUINO >= 100) #include #else #include //#define Wire.write(x) Wire.send(x) //#define Wire.read() Wire.receive() #endif static uint8_t nunchuck_buf[6]; // array to store nunchuck data, // Uses port C (analog in) pins as power & ground for Nunchuck static void nunchuck_setpowerpins() { #define pwrpin PORTC3 #define gndpin PORTC2 DDRC |= _BV(pwrpin) | _BV(gndpin); PORTC &= ~ _BV(gndpin); PORTC |= _BV(pwrpin); delay(100); // wait for things to stabilize } // initialize the I2C system, join the I2C bus, // and tell the nunchuck we're talking to it static void nunchuck_init() { Wire.begin(); // join i2c bus as master Wire.beginTransmission(0x52);// transmit to device 0x52 #if (ARDUINO >= 100) Wire.write((uint8_t)0x40);// sends memory address Wire.write((uint8_t)0x00);// sends sent a zero. #else Wire.send((uint8_t)0x40);// sends memory address Wire.send((uint8_t)0x00);// sends sent a zero. #endif Wire.endTransmission();// stop transmitting } // Send a request for data to the nunchuck // was "send_zero()" static void nunchuck_send_request() { Wire.beginTransmission(0x52);// transmit to device 0x52 #if (ARDUINO >= 100) Wire.write((uint8_t)0x00);// sends one byte #else Wire.send((uint8_t)0x00);// sends one byte #endif Wire.endTransmission();// stop transmitting } // Encode data to format that most wiimote drivers except // only needed if you use one of the regular wiimote drivers static char nunchuk_decode_byte (char x) { x = (x ^ 0x17) + 0x17; return x; } // Receive data back from the nunchuck, // returns 1 on successful read. returns 0 on failure static int nunchuck_get_data() { int cnt = 0; Wire.requestFrom (0x52, 6);// request data from nunchuck while (Wire.available ()) { // receive byte as an integer #if (ARDUINO >= 100) nunchuck_buf[cnt] = nunchuk_decode_byte( Wire.read() ); #else nunchuck_buf[cnt] = nunchuk_decode_byte( Wire.receive() ); #endif cnt++; } nunchuck_send_request(); // send request for next data payload // If we recieved the 6 bytes, then go print them if (cnt >= 5) { return 1; // success } return 0; //failure } // Print the input data we have recieved // accel data is 10 bits long // so we read 8 bits, then we have to add // on the last 2 bits. That is why I // multiply them by 2 * 2 static void nunchuck_print_data() { static int i = 0; int joy_x_axis = nunchuck_buf[0]; int joy_y_axis = nunchuck_buf[1]; int accel_x_axis = nunchuck_buf[2]; // * 2 * 2; int accel_y_axis = nunchuck_buf[3]; // * 2 * 2; int accel_z_axis = nunchuck_buf[4]; // * 2 * 2; int z_button = 0; int c_button = 0; // byte nunchuck_buf[5] contains bits for z and c buttons // it also contains the least significant bits for the accelerometer data // so we have to check each bit of byte outbuf[5] if ((nunchuck_buf[5] >> 0) & 1) z_button = 1; if ((nunchuck_buf[5] >> 1) & 1) c_button = 1; if ((nunchuck_buf[5] >> 2) & 1) accel_x_axis += 1; if ((nunchuck_buf[5] >> 3) & 1) accel_x_axis += 2; if ((nunchuck_buf[5] >> 4) & 1) accel_y_axis += 1; if ((nunchuck_buf[5] >> 5) & 1) accel_y_axis += 2; if ((nunchuck_buf[5] >> 6) & 1) accel_z_axis += 1; if ((nunchuck_buf[5] >> 7) & 1) accel_z_axis += 2; Serial.print(i, DEC); Serial.print("\t"); Serial.print("joy:"); Serial.print(joy_x_axis, DEC); Serial.print(","); Serial.print(joy_y_axis, DEC); Serial.print(" \t"); Serial.print("acc:"); Serial.print(accel_x_axis, DEC); Serial.print(","); Serial.print(accel_y_axis, DEC); Serial.print(","); Serial.print(accel_z_axis, DEC); Serial.print("\t"); Serial.print("but:"); Serial.print(z_button, DEC); Serial.print(","); Serial.print(c_button, DEC); Serial.print("\r\n"); // newline i++; } // returns zbutton state: 1=pressed, 0=notpressed static int nunchuck_zbutton() { return ((nunchuck_buf[5] >> 0) & 1) ? 0 : 1; // voodoo } // returns zbutton state: 1=pressed, 0=notpressed static int nunchuck_cbutton() { return ((nunchuck_buf[5] >> 1) & 1) ? 0 : 1; // voodoo } // returns value of x-axis joystick static int nunchuck_joyx() { return nunchuck_buf[0]; } // returns value of y-axis joystick static int nunchuck_joyy() { return nunchuck_buf[1]; } // returns value of x-axis accelerometer static int nunchuck_accelx() { return nunchuck_buf[2]; // FIXME: this leaves out 2-bits of the data } // returns value of y-axis accelerometer static int nunchuck_accely() { return nunchuck_buf[3]; // FIXME: this leaves out 2-bits of the data } // returns value of z-axis accelerometer static int nunchuck_accelz() { return nunchuck_buf[4]; // FIXME: this leaves out 2-bits of the data } int loop_cnt = 0; byte joyx, joyy, zbut, cbut, accx, accy, accz; void _print() { Serial.print("\tX Joy: "); Serial.print(map(joyx, 15, 221, 0, 255)); Serial.print("\tY Joy: "); Serial.println(map(joyy, 29, 229, 0, 255)); } int joyx1 = 129; // 15 - 221 int joyy1 = 124; // 29 - 229 void setup() { Serial.begin(9600); nunchuck_setpowerpins(); nunchuck_init(); // send the initilization handshake Serial.println("Wii Nunchuck Ready"); pinMode(3, OUTPUT); pinMode(5, OUTPUT); pinMode(6, OUTPUT); pinMode(9, OUTPUT); //type(); } void loop() { if ( loop_cnt > 10 ) { // every 100 msecs get new data loop_cnt = 0; nunchuck_get_data(); zbut = nunchuck_zbutton(); joyx = nunchuck_joyx(); // 15 - 221 joyy = nunchuck_joyy(); // 29 - 229 _print(); } loop_cnt++; if (zbut == 1) { type(); zbut = 0; } else { if (joyx > (joyx1 + 20)) { int speed1 = map(joyx - joyx1, 0, 80, 40, 255); speed1 = constrain(speed1, 0, 255); analogWrite(6, 0); analogWrite(9, speed1); } else if (joyx < (joyx1 - 20)) { int speed2 = map(joyx1 - joyx, 0, 90, 40, 255); speed2 = constrain(speed2, 0, 255); analogWrite(6, speed2); analogWrite(9, 0); } else { analogWrite(6, 0); analogWrite(9, 0); } if (joyy > (joyy1 + 20)) { int speed3 = map(joyy - joyy1, 0, 80, 40, 255); speed3 = constrain(speed3, 0, 255); analogWrite(3, 0); analogWrite(5, speed3); } else if (joyy < (joyy1 - 20)) { int speed4 = map(joyy1 - joyy, 0, 90, 40, 255); speed4 = constrain(speed4, 0, 255); analogWrite(3, speed4); analogWrite(5, 0); } else { analogWrite(3, 0); analogWrite(5, 0); } } delay(1); } void type() { int rltime = 200; //digitalWrite(6, 1);//origin //digitalWrite(9, 0); //digitalWrite(3, 1); //digitalWrite(5, 0); //delay(1000); //H============== //digitalWrite(3, 0);//wait //digitalWrite(5, 0); //digitalWrite(6, 0); //digitalWrite(9, 0); //delay(250); //digitalWrite(3, 0);//up digitalWrite(5, 1); delay(500); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); digitalWrite(3, 1);//down //digitalWrite(5, 0); delay(250); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); //digitalWrite(6, 0);//right digitalWrite(9, 1); delay(rltime); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); //digitalWrite(3, 0);//up digitalWrite(5, 1); delay(250); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); digitalWrite(3, 1);//down //digitalWrite(5, 0); delay(500); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); //digitalWrite(6, 0);//right digitalWrite(9, 1); delay(rltime); //I======================== digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); digitalWrite(3, 0);//up digitalWrite(5, 1); delay(500); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); digitalWrite(6, 0);//right digitalWrite(9, 1); delay(100); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); digitalWrite(6, 1);//left digitalWrite(9, 0); delay(rltime); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); digitalWrite(6, 0);//right digitalWrite(9, 1); delay(100); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); digitalWrite(3, 1);//down digitalWrite(5, 0); delay(500); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); digitalWrite(6, 0);//right digitalWrite(9, 1); delay(100); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); digitalWrite(6, 1);//left digitalWrite(9, 0); delay(rltime); digitalWrite(3, 0);//wait digitalWrite(5, 0); digitalWrite(6, 0); digitalWrite(9, 0); delay(250); }
Calibrate
Turn on the device:
- Plug in the controller
- Attach the battery
- Make sure everything is oriented correctly: the x-axis motor should respond to the x-axis of the controller, the motors should travel the direction you want them to, etc... - if something seems off, just power everything down and switch some motor wires around.
Once everything is working, control should be relatively intuitive:
- Control direction and speed with the joystick
- Press the "z" button to spell out "HI" (pre-programmed)
Notes
Here are a few other things you can try:
- Use a different controller (maybe an accelerometer for tilt control)
- Replace the gear motors with steppers for greater accuracy
- Make a program to draw pre-programmed pictures
- Add a tilt mechanism to allow for automatic erasing