Hello Vibrating Motors

Acronyms

• ERM: Eccentric Rotating Mass. These are the older vibrators we’re used to from flip phones.
• LRA: Linear Resonance Actuators. These are the newer, more sophisticated models like Taptic Engine on Apple devices, which have no startup delay.

Project 1: Hello Vibes

Following this circuit diagram reference, omitting the TIP 120 transistor & diode since they weren’t available:

It worked! For now, the hardware is the simple breadboard with the ERM motor, which I’m holding between my index finger and thumb to feel acutely.

I tried different combinations of vibrations & delays.

• 10ms on, 50ms off was the minimum I could sense distinct vibrations, instead of a more continuous purr from the ERM
• 15ms on/50ms delay gives me more to feel
• Even intervals like 50ms/50ms create an industrial energy, like a sewing machine
• I LOVE the intervening fade in/out the ERM performs while I’m uploading new software to the Arduino. Wish I knew how to replicate that gradient

My favorite iteration made the vibration feel like my parents’ Motorola flip phones from the early 2000s. I did buzzes for 50, 100, 250, 500, and 500ms again with 100ms delays in between, like this:

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(50);
  digitalWrite(LED_BUILTIN, LOW);
  delay(100);

  digitalWrite(LED_BUILTIN, HIGH);
  delay(100);
  digitalWrite(LED_BUILTIN, LOW);
  delay(100);

  digitalWrite(LED_BUILTIN, HIGH);
  delay(250);
  digitalWrite(LED_BUILTIN, LOW);
  delay(100);

  digitalWrite(LED_BUILTIN, HIGH);
  delay(500);
  digitalWrite(LED_BUILTIN, LOW);
  delay(100);

  digitalWrite(LED_BUILTIN, HIGH);
  delay(500);
  digitalWrite(LED_BUILTIN, LOW);
  delay(100);
}

Here’s how it looked:

Project 2: Haptic Motor Driver

Following this circuit diagram:

Here’s how my circuit looked:

I used the Adafruit DRV2605 from the ITP shop.

I’ve never paid super close attention to the Apple Watch haptic alarm that wakes me up for class every day, since I always want to turn it off & I’m inherently bleary-eyed if I needed the alarm. Nonetheless, I wanted to make an alarm that’d be reasonable to wake up to:

#include <Wire.h>
#include "Adafruit_DRV2605.h"

Adafruit_DRV2605 drv;

void setup() {
  Serial.begin(9600);
  Serial.println("DRV test");
  drv.begin();

  drv.setMode(DRV2605_MODE_INTTRIG); // default, internal trigger when sending GO command

  drv.selectLibrary(1);
  drv.setWaveform(0, 86);

  // shorter
  drv.setWaveform(0, 84);
  drv.setWaveform(0, 74);

  // longer
  drv.setWaveform(0, 82);
  drv.setWaveform(0, 72);

  // two clicks
  drv.setWaveform(1, 1);
  drv.setWaveform(1, 9);

  drv.setWaveform(2, 0);  // end of waveforms
}

void loop() {
    drv.go();
    delay(1000);
}

I wanted to use distinct pieces, not a continuous sensation; the frequent deltas between sensations is more noticeable to wake up to than there being one change the body can get used to. I paired the ramp up with ramp down codes to create increasing little bursts of vibration in a repeating loop. I modeled it after the Apple Watch haptic, though it’s not trying to be a precise replica.

Project 3: Motor Array

Following this circuit diagram:

First, I set up my circuit using the terminal blocks:

Next, I soldered the three haptic motors to longer wires, so the device could become more wearable:

Here’s my code. I took the example and added a section to try two motors at once, then turn everything off, before repeating.

void setup () {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
}

void loop() {
  // turn all motors on (HIGH is the voltage level)
  digitalWrite(2, HIGH);
  digitalWrite(3, HIGH);
  digitalWrite(4, HIGH);
  // wait for a second
  delay(1000);
  // turn all motors off
  digitalWrite(2, LOW);
  digitalWrite(3, LOW);
  digitalWrite(4, LOW);
  delay(1000);

  // turn motors on one at a time
  digitalWrite(2, HIGH);
  delay(1000);
  digitalWrite(2, LOW);
  digitalWrite(3, HIGH);
  delay(1000);
  digitalWrite(3, LOW);
  digitalWrite(4, HIGH);
  delay(1000);
  digitalWrite(4, LOW);
  delay(1000);

  // turn sets of two motors on
  digitalWrite(2, HIGH);
  digitalWrite(4, HIGH);
  delay(1000);
  digitalWrite(2, LOW);
  digitalWrite(3, HIGH);
  delay(1000);
  digitalWrite(2, HIGH);
  digitalWrite(4, LOW);
  delay(1000);

  // turn all motors off
  digitalWrite(2, LOW);
  digitalWrite(3, LOW);
  digitalWrite(4, LOW);
｝

Ideas for projects tomorrow

• Make inchworms with two haptic engines on either end, see if they can wriggle across a table if synced well
• Storytelling in a diorama with knocking on a door with the haptics & sound effects on the Arduino
• Apple Vision Pro haptics soundboard—website or visionOS app?

Final project: Shareable Haptic Experience