For enhancing the sense of movement in VR, a custom vibrotactile module has been developed with out-of-the-box components including an Arduino board. The vibrotactile module can function as a valuable feedback modality for promoting induced illusions  relying on the sensorimotor contingencies between perception and action, useful in motor-imagery training in BCI.

This module is composed by three main components:

1. Arduino board
2. Vibrating motors
3. Cylindrical tubes

1. Arduino board setup:

For connecting the Arduino board with the motors (see figure 1(a)), the following components are needed:

• 1N4001 Diode
• 0.1µF ceramic capacitor
• 1KΩ Resistor
• 2N2222 NPN Transistor
• USB Connector

Figure 1 (a): Circuit schematic for 1 motor

Figure 1 (b): Complete circuitry for 6 motors

2. Vibrating tubes

– For installing the motors inside the tubes, a 3D printed case has been designed (STL model) in order to accommodate the motor before inserted inside the tube (see figure 2).

Figure 2 (a): 3D model of the motor casing

Figure 2 (b): Motor inserted inside the 3D printed case

– Cylindrical tubes act as grasping objects for simulating the rows movement. For our setup, a pair of carton based tubed had been used with 12cm of length, 3cm diameter and 0.5cm of thickness (see figure 3).

Figure 3 (a): Cylindrical tube schematic with dimensions

Figure 3 (b): Complete tube with  motor installed

3. Technical specifications

Vibrating Motor Specs

Arduino Mega 2560

Microcontroller	ATmega2560
Operating Voltage	5V
Input Voltage (recommended)	7-12V
Input Voltage (limit)	6-20V
Digital I/O Pins	54 (of which 15 provide PWM output)
Analog Input Pins	16
DC Current per I/O Pin	20 mA
DC Current for 3.3V Pin	50 mA
Flash Memory	256 KB of which 8 KB used by bootloader
SRAM	8 KB
EEPROM	4 KB
Clock Speed	16 MHz
Length	101.52 mm
Width	53.3 mm
Weight	37 g

Finally, upload the following code to the Arduino board for controlling the motors through NeuRow:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36

String str;
int values[2][6];
int power = 0;
int hand = 0;
int finger = 0;

void setup()
{
  Serial.begin(9600);
  Serial.flush(); //clears any possible left over information
}

void loop()
{
  if(Serial.available() > 0)
  {
      str = Serial.readStringUntil(';');
      power = str.toInt();
      
      str = Serial.readStringUntil(';');
      hand = str.toInt();
      
      str = Serial.readStringUntil(';');
      finger = str.toInt();
      
      values[hand][finger] = power;
  }
  
  for(int i = 0; i <2; i++)
  {
    for(int j = 0; j < 6; j++)
    {
      analogWrite(i*6+j+2, values[i][j]);
    }
  }
}