Figure 1. Optical Shaft Encoder disk.
The Optical Shaft Encoder can be used to improve a robot in various ways. The encoder can measure rotational distance traveled and speed, which can be used to monitor, for example, the angular position of a robot gripper arm or the speed of a robot. Knowing these parameters can greatly assist you with performing autonomous tasks with your robot.
The Optical Shaft Encoder can be used to track distance traveled, direction of motion, or position of any rotary component, such as a gripper arm. The encoder can also be used to detect movement, which could facilitate richer interaction between the robot and its environment (e.g., human-robot interaction). If a human moves a robot arm that is attached to an encoder (e.g., during a handshake), the robot detects the arm movement and the direction(s) and distance(s) traveled, helping the robot classify the interaction as a handshake.
Figure 2. Optical Shaft encoder mounting system
While the diameter of the disk in the encoder does not really matter, the diameter of the wheel or gear whose shaft passes through the encoder does! The circumference of the wheel is equal to its diameter multiplied by pi (approx. 3.14). Multiplying the distance traveled which when multiplied by the number of revolutions gives of the distance traveled.
Figure 3. Wheel circumference formula
The optical shaft encoder can detect up to 1,700 pulses per second, which corresponds to 18.9 revolutions per second and 1,133 rpm (revolutions per minute). Faster revolutions will therefore not be interpreted exactly, potentially resulting in erroneous positional data being passed to the microcontroller.
- Compatible with all VEX microcontrollers and 3-Wire Extension Cables
- Inputs: Type: Mechanical Rotation
- Outputs: 3-Wire Cable
- Function: Sensor - Infrared light sensor and infrared LED, Encoder Wheel has 90 slits
- Weight: 0.078 lbs (35.4 grams)
Size: Standard VEX 1/8 in shaft
Connect to two interrupt inputs.
White: Control Signal
Cortex Resolution - 1 degree
PIC Resolution - 2 degrees with ROBOTC, 4 degrees with easyC and easyC PRO