About this project
Project Status
PCB designed - Done!
Prototype construction - Done!
Testing - In progress...
The Project
We are offering a product that we had to design for our own manipulators for the FIRST Robotics Competition. We first started the concept of an Arbitrary Quadrature Encoder a couple years ago when we needed to extend an arm several feet in the air and needed to know when it reached a certain height. It took way too long to develop and was a huge ugly circuit when we were finished. So we decided to make it more elegant and functional by continuing development towards a mass-produced unit that will be available to other robotics teams and makers around the world.
There are many quadrature encoders that are commercially available, each offering precision and impressive specifications with the caveat of being properly installed. With many prototype projects in general, and high-school robotics in particular, proper installation is not likely nor guaranteed. From flexible shafts to cantilevered shafts, or motors with no suitable shaft to attach to, it is often quite difficult to find a suitable mount for commercially available encoders. Likewise, gearboxes with up to several degrees of backlash tend to give very noisy feedback signals from high-resolution encoders.
This encoder project gets around these problems by setting goals of simplicity and robustness. The board encodes two channels, using reflection off of an easy-to-make encoder strip or disk. The resolution is arbitrary, and governed only by the size of the black and white stripes of the encoder strip. The mounting can be skewed and the stripe width varied for finer or coarser resolution. Two feedback LED's inform the user that the encoder strip is located within the proper sensing distance, by giving the detected state.
Our current proof-of-concept is a wire-wrapped PC board constructed with much more precision than our original version (thanks to soldering and wiring training from volunteers at Edwards Air Force Base). This board has demonstrated success in its proof-of-concept form by successfully providing feedback to a CAN-controlled FIRST Jaguar motor controller, smoothly and accurately controlling the speed of an automotive window regulator motor.
We are now on the next step, creating a mass-produced encoder. We have assembled a few pre-production prototypes (pictured in our updates) and are currently testing. We expect to complete the prototype development by May 31st, at which point, we will move into production.
While we love our new encoder, we don't need the hundreds that would make the printing/assembly process economical, so we are offering our new device to you to help share the costs. Backers of our Arbitrary Optical Encoder project will receive finished products - printed circuit boards with surface mount technology, ready to be incorporated into their maker or robotics projects. If you've ever needed to control a motor based on feedback from a less than precise source, this is the project for you.
About the Arbitrary Quadrature Encoder
By designing an optical quadrature encoder, FIRST Team 585 is able to address limitations of the currently available commercial encoders. Typical commercial encoders are limited by high resolution and the need for perfection of the shaft. However, our Arbitrary Quadrature Encoder enables users to customize their resolution and place the almost anywhere along the actuation path.
This circuit is implemented using infrared emitters and detectors. The encoder strip of alternating black and white blocks can be printed with any printer on plain printer paper. As the stripes travel past the emitters and detectors, the encoder's comparators will be able to sense changes in color value and adjust the voltage between a high and low digital signal on the output. In addition to the two channels of quadrature encoding, there will be a two-pin header to attach to an external microswitch, to provide an index signal. All power and signals will be externally available through a five-pin header, in the same arrangement as used in the FIRST Jaguar motor controller. Although this is designed for direct interface to the FIRST Jaguar, the encoder could be connected to a Digital Sidecar or any other digital IO device that utilizes TTL.
The Arbitrary Quadrature Encoder just needs a hub with striping and the detector circuit placed a fraction of an inch away. Commercially available optical encoders are highly sensitive focal lengths and shaft vibrations, which generate inaccurate readings and can even destroy the encoder. With the Arbitrary Quadrature Encoder, observations are much less sensitive because the lower resolution and the fact that the detector can be placed further away from the encoder disk or strip.
About FIRST Team 585, the Cyber Penguins:
It is our vision that: "through hands-on exposure to STEM, students become critical thinkers, skilled technicians, and leaders of innovation." As such it is our mission to "in partnership with our school, community, and industry, provide opportunities for students of all ages to learn skills in STEM through hands-on experiences and exposure to applications of engineering." In this vein, we encourage our members to pursue projects that help them learn and add to the common knowledge of all students.
Our program and outreach events impact hundreds of students in the Tehachapi and high desert areas, hopefully pointing them towards careers in Science, Technology, Engineering and Mathematics. This is our first Kickstarter venture, but we are hoping that success with this development of a student project will encourage our team members to be more innovative and continue with the innovation cycle for their interests.
Risks and challenges
Construction of the prototype is currently underway and is anticipated to be completed by the end of the time line for our project. We will continue to update the project with prototype developments as they occur. So far, the parts that we are using are readily available and we do not anticipate delays in the schedule for prototype production.
We have located a supplier for printing and assembling the boards for us, but they do use international manufacturers for some of the process. Depending on natural or other disasters, we could have delays in production. However, we believe we have included a sufficient buffer time in our delivery cycle to allow for any manufacturing delays.
We will be assembling and testing the cables ourselves. We have a lot of experience with making our own cables, but it's hard to predict productivity with a batch of high schoolers, especially with summer vacation looming. However, we believe that we've incorporated the time necessary for training, cable construction, testing and troubleshooting into our September delivery window.
Learn about accountability on KickstarterFAQ
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No. While we have designed this encoder to plug directly into a Jaguar, it can plug into any digital input port that uses TTL or CMOS logic levels. In FRC applications, it can be plugged into one, two or three DIO ports on the digital sidecar for one channel, quadrature, or indexed operation. By processing feedback on the cRIO, you can use this encoder with motors controlled by Talons or Victors, like any other encoder.
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We suggest a distance of .15" (~4mm) between the encoder and the encoder strip. It will function at closer distances as well as slightly further distances. It is relatively forgiving.
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Funding period
- (30 days)