Optical encoders

http://www.alibaba.com/product-detail/optical-encoder-sensors_503181569.html

http://xinhsen.en.alibaba.com/product/60388368790-801358871/photo_etching_customized_encoder_disk_for_sensor.html Xinhaisen technology

AMS

 * https://www.youtube.com/watch?v=DQdHslX-5Lo ,
 * http://ams.com/eng/Products/Position-Sensors/Magnetic-Rotary-Position-Sensors/AS5145H
 * https://www.youtube.com/watch?v=jbcPydrh0aA AS5045 ARDUINO CODE
 * http://ghostgimbals.com/  as5048B 14bit used with AlexMoss Gimbal controller.
 * http://madscientisthut.com/forum_php/viewtopic.php?f=11&t=7 arduino code as5040 . Reading serial bits.
 * http://reprap.org/wiki/Magnetic_Rotary_Encoder_v1.0 as5040 description, code and surface soldering
 * http://www.rottorteam.com/shop/encoders/as5048/ used with Gimbal
 * http://eu.mouser.com stocks 600 as5048a chips
 * http://www.mouser.com/ds/2/588/ams_AS5048-EK-AB-STM1-341286.pdf design kit 985-AS5048A-EK-AB  for datasheet. Use Dexter diametric magnet part 2910041-1. Diametric means north south poles, 6mm width x 3mm thick.
 * http://dangerousprototypes.com/forum/viewtopic.php?f=56&t=3669 Read SPI on rising edge, data latched on falling edge.

Quantum devices
https://quantumdevices.wordpress.com/2012/01/26/the-use-of-potentiometers-in-incremental-encoder-design/ Quantum Devices is now proud to introduce it's new line of rotary encoders. Incorporating QDI's patented sensor technology, our QPhase™. Pictures contain https://www.yaskawa.com/pycprd/home chipset. Yaskawa has patents on optical encoders, driving up the price of these devices. See https://patents.google.com/patent/US7348543B2/en
 * https://patents.google.com/patent/US7348543B2/en termination resistors on long cables.
 * http://abrobotics.tripod.com/Ebot/using_encoder.htm tutorial code

Drexel
https://www.youtube.com/watch?v=xgIubJHVRwg, http://dasl.mem.drexel.edu/~jiyueHe/rotary_inverted_pendulum/ Rotary inverted pendulum, full code PID on arduino mega.

HEDS 9000
https://www.youtube.com/watch?v=T5Xyt7vcOo8 HEDS 9000  http://www.bristolwatch.com/arduino/arduino2.htm arduino interrupts