Wheel Encoder

Product Description

Description: This
quadrature encoder board is designed to hold two infrared reflectance
sensors inside the hub of the 42x19mm wheel and measure the movement of
the twelve teeth along the wheel?s rim. The
two sensors are spaced to provide waveforms approximately 90 degrees
out of phase, allowing the direction of rotation to be determined and
providing four counts per tooth for a resolution of 48 counts per wheel
rotation. Each analog sensor signal is fed to a comparator with
hysteresis to provide glitch-free digital outputs. The compact layout
of the board fits all of the components within the envelope of the hub
and tire, allowing the board to be mounted between the motor and a
chassis. The encoder is calibrated for operation from 4.5 V to 5.5 V,
but it can be recalibrated for operation at 3.3V .

The two outputs of the encoder are digital outputs that can be
connected directly to digital input pins on most microcontrollers
(inputs that can generate interrupts on change are recommended). With 48 state changes per revolution of the 42 mm wheel, a speed of 1 m/s (a
bit over 3 feet per second) generates approximately 360 state changes
per second. With two encoders used simultaneously, as is the case for
most differential-drive robots, the encoders will require attention
almost every millisecond. Decoding the encoder outputs should only take
a few percent of the processing power of a
microcontroller such as the Atmel ATMega168.

Features:

• 4.5-5.5V operating voltage
  
• 2 digital outputs
  
• 14mA consumption at 5V
  
• 48 counts per revolution (linear resolution just under 3mm)
  
• 2A continuous paralleled output current
• 100kHz maximum PWM frequency
• 2.7-5.5VDC logic voltage

• AVR C/C++ Library
• AVR C/C++ Library Commands