Organize and Share your Electronics the way you want. Sign-Up for a free account now. It takes only 30 seconds!

Make an Optical Encoder

Make an Optical Encoder

An optical encoder measures how far something has moved, optically. It does this by looking at a pattern of alternating black-and-white, and counting number of transitions.
A typical optical encoder will either use a break-beam sensor, or a singlepattern (dual for quad-phase) of alternating black and white. This is donebecause most designs are in a well-controlled environment, where there arereasonably well known, fixed levels for dark and light. In this case, we had afar less controlled environment:

  • The optical encoder went directly on the wheel. As a result, there was an ambient light level that varied by several orders of magnitude.
  • The optical encoder disk could be positioned at different distances from the sensor.
  • The optical encoder disk could be printed on a variety of printers, where toner may either be more or less reflective than paper, by varying amounts.

For these reasons, traditional hobbyist optical encoders tend to be completedisasters. To mitigate some of these problems, we used a differential design. Inso much as the photosensors matched, so that the design was very insensitive toambient light level, or how much light was reflected from the surface, so longas different amounts of light were reflected.

Using the phototransistors back-to-back as a voltage divider (rather thanamplifying first) let the design to have a huge dynamic range.

The major disadvantage of the differential design was decreased resolution.We needed four rings for a quad-phase design, instead of two. As a result, theinner-most ring was on a much smaller radius, and so could not have very densestripes. In addition, the photosensors needed to be reasonably well matched.

Visit Here for more.

 

More Articles to Read

#FreePCB via Twitter to 2 random RTs
#FreePCB via Twitter to 2 random RTs
Estimating Power for ADSP-BF561 Blackfin® Processors
Estimating Power for ADSP-BF561 Blackfin® Processors
Teach Your Arduino to Switch Itself Off!
Teach Your Arduino to Switch Itself Off!
Control a tracked robot with your mind (or joystick)
Control a tracked robot with your mind (or joystick)
A 400W (1kW Peak) 100A electronic load using linear MOSFETs
A 400W (1kW Peak) 100A electronic load using linear MOSFETs
Shirt Pocket Transceiver with the Si5351 and OLED
Shirt Pocket Transceiver with the Si5351 and OLED
All metal C930e webcam
All metal C930e webcam
The Soldering Tools That Make Your Life Easier
The Soldering Tools That Make Your Life Easier
App note: Operation evaluation of ultra low ON resistance MOSFET supporting quick charge for 1 c ...
App note: Operation evaluation of ultra low ON resistance MOSFET supporting quick charge for 1 cell Lithium ion battery protection
Synthesized Sidetone
Synthesized Sidetone

Top




Shares