Servo - November 2011

FIGURE 8. A wireless version of VEX control glove with three flexible resistors, two potentiometers, and five pushbutton switches connected to the VEX RC receiver.

time. I do plan to obtain its position indoors by using a combination of ultrasonic PING))) sensors or Polaroid 6500 sonar rangers with Time of Flight (TOF) and trilateration or triangulation techniques to calculate the glove’s position in 3D. Another alternative would be to implement a low cost gyro and accelerometer combination board (IMU) used for RC helicopters to keep track of the glove’s position and orientation.

Finger Positions

The control glove’s fingers allow you to move distant objects by just bending your index finger with natural motions. The finger positions are read using the microcontroller’s 10-bit ADC to digitize the voltages that are generated by bending the flexible resistors; this changes the resistance depending upon how much each resistor is bent. In order to obtain the best readings possible, each finger is individually calibrated by having the operator move it from its minimum position to its maximum position, then the voltages are recorded so that they can be used to calibrate the finger position data. The finger positions are mapped by the remote application

FIGURE 9. A wireless glove is the perfect companion to controlling VEX robots such as the Telepod tripod (photographer's assistant).

52 SERVO 11.2011

using the calibration data so that each finger position can move the individual servo or motor (or multiple servos or motors).

Pushbuttons

Five small pushbuttons (shown in Figure 8) provide functionality similar to a PC joystick trigger and fire buttons, but also allow the wearer to select which motors to move or which lights to turn on/off. The pushbuttons can be read and de-bounced using the Easy C Pro digital input function firmware for the IO11-IO16 digital input pins. Pushbutton switches are of the miniature PCB variety. Each is hot glued to each forefinger or knuckle so that it is easily accessible from the user’s other hand. Each pushbutton switch on the glove is wired to the digital inputs I011 through IO16 of the microcontroller using wire-wrap wire.

The pushbutton switches can be assigned to perform a task on the microcontroller as shown in Table 2.

How It Works

The system consists of the microcontroller and glove to digitize the finger positions (flexible resistors) and the glove’s orientation. It works by having the Easy C Pro firmware simply digitize the glove’s finger positions by reading the voltages across the flexible resistors whose resistance varies with the angle that each finger is bent or flexed. The wearer’s own finger movements are digitized