Project Logs

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• Overview Video

  oneohm • 10/10/2023 at 08:13 • 0 comments

• Cost Estimates and Scaling

  oneohm • 10/09/2023 at 22:30 • 0 comments

  The design is intended to be simple enough that a wide variety of people will be able to construct one at home or in a maker space. 

  Depending on the modules and accessories selected when building an OHMni-Stick, it can be built for around $80 USD in materials. However some of the parts (screws, threaded inserts, etc.) are only available in larger quantities, so the total cost will be closer to $150-$200 USD.

  My hope is that there will be enough interest in the OHMni-Stick that it will be possible to arrange build events, or to put together parts kits to make it easier for others to make. If the parts are ordered wholesale in larger quantities, I believe the raw materials can be acquired for less than $50 USD.

  Considering that commercial products with similar functionality often cost several thousand dollars, I feel that the OHMni-Stick is a great value. 

• Mouth and Tongue Control with "Sip and Puff"

  oneohm • 10/09/2023 at 21:26 • 0 comments

  I'm excited to share the latest addition to the OHMni-Stick project: a new module that empowers users to operate the device using their mouth or tongue. This module also integrates "sip and puff" pressure sensitive controls, providing an alternative input method for users who may not be able to use their hands.
  

  Enhancing Accessibility for All
  

  Accessibility is at the heart of the OHMni-Stick project, and this new module takes it to a whole new level. It enables individuals facing a wide range of mobility challenges to control the device with remarkable precision and ease.

  Mouth and Tongue Control: A Game-Changer

  Our new module allows users to control the OHMni-Stick by simply using their mouth or tongue. It's a testament to the power of technology in breaking down barriers. Whether someone faces limitations with their hands or upper body, they can now enjoy the freedom and independence that the OHMni-Stick provides.

  Join Us on the Journey

  The OHMni-Stick journey is ongoing, and we're excited to have you with us. Your contributions, ideas, and feedback continue to drive this project forward. Whether you have a specific need, an idea for improvement, or a creative adaptation, we encourage you to explore, innovate, and share your insights.

• Mounting Options

  oneohm • 10/08/2023 at 19:36 • 0 comments

  The Ohmni-Stick can be used standalone on a flat surface, or for more secure mounting in different orientations the enclosure includes a 1/4"-20 threaded insert. This mounting point is compatible with a wide range of clamps, tripods, and articulated arms typically used for camera gear. 

  For testing I have found an 11 inch articulating friction arm with a desk clamp is a great option.

• Firmware

  oneohm • 10/07/2023 at 22:12 • 0 comments

  The OHMni-Stick firmware utilizes the Arduino framework and is being developed as a PlatformIO project.

  Using the familiar and widely accessible Arduino framework and libraries should make it easy to adapt and modify the code to suit new use cases or add new functionality.

  The firmware emulates a generic USB HID mouse and has been tested to work with computers, tablets and phones when using a USB OTG adapter.

  Like the rest of this project the code is provided freely as open source.

• KiCad Schematics and PCB Design

  oneohm • 10/07/2023 at 22:01 • 0 comments

  To ensure the design is as open and accessible as possible, the circuit board design was created using KiCad, a free and open source PCB design package. 

  Simplicity and ease of assembly were primary drivers for the design. The board can be fabricated as an affordable two layer board, and can even be hand-made as a single layer board using toner-transfer or other home-fabrication methods.

  All of the original design files, schematics and the board fabrication outputs (Gerbers/Drill files) are freely available.

  Schematics:

  Amplifier Module Reference Schematics:

  The load cell amplifier modules are a widely available commodity part. They appear to be a faithful implementation of the circuit suggested in the HX711 datasheet:
  

  SAMD21 XIAO module schematic:

  The microcontroller module is made by seeed studio and the full schematic for that part is available here: XIAO Schematic

  Board Layout:

• FreeCAD model

  oneohm • 10/07/2023 at 21:39 • 0 comments

  The OHMni-Stick 3D model was created in FreeCAD, a free and open source CAD package. 

  A modular design approach makes it easy to make new, swappable modules and accessories. 

  This adaptability ensures that the OHMni-Stick can evolve with user needs, fostering continuous improvement and customization.

  The full model is available for download with the hope that people will continue to adapt and modify the design in ways that will fulfill the needs of more and more users.

• Pneumatic Pressure-Sensitive Buttons

  oneohm • 05/29/2023 at 22:10 • 0 comments

  This update on the OHMni-Stick project focuses on the pneumatic pressure-sensitive buttons. These buttons offer a comfortable and responsive input method, designed to enhance the user experience.

  Each button consists of a silicone tubing "pillow" sealed with RTV silicone at the ends. The sealed ends are securely squeezed between layers of laser-cut acrylic and fastened with M3 screws, ensuring durability and stability. Underneath each button is an affordable and widely available pressure sensor module, snugly pressed into a small hole pierced into the silicone "pillow."

  The sensor modules feature an AVIA HX710B 24-bit ADC module, enabling accurate and reliable pressure detection. This high-resolution ADC module ensures precise measurement and responsiveness, detecting the lightest touch to the heaviest blow.

  One of the key advantages of these buttons is their adjustable sensitivity. By adjusting the activation threshold pressure, users can customize the buttons to their preferences, providing a personalized and comfortable user experience. It is also possible to configure the buttons to respond to multiple pressure levels, for instance light, normal, and firm click modes.

  These pneumatic pressure-sensitive buttons offer a robust and tactile interface, delivering precise control for various applications. They complement the low force and displacement joystick, creating a comprehensive and intuitive control system.

  With the integration of these innovative buttons, the OHMni-Stick empowers individuals with disabilities or limited mobility to interact with technology in a way that is accessible, responsive, and engaging. It opens up new possibilities for enhanced interaction and independence. I am proud to contribute to a more inclusive and accessible world through this project.

• Objective Force and Displacement Measurements

  oneohm • 05/26/2023 at 23:54 • 0 comments

  Now for some objective measurements of the OHMni-Stick's sensitivity, specifically the force and displacement requirements. To accurately assess its performance, I conducted some initial tests using an IMADA DPS-11 digital force gauge in combination with a Mitutoyo SD displacement gauge for precise characterization.
  

  The current prototype of the OHMni-Stick proved to be highly sensitive and responsive, reliably responding to forces as low as those measurable by the IMADA force gauge (+/-1gram). This means that even individuals with extremely limited muscle strength can effortlessly utilize the OHMni-Stick to control devices and engage in various activities.

  Additionally, the displacement measurements were equally impressive. Even when a force of 1Kg was applied, the recorded displacement was only 0.2mm. This minimal movement requirement is particularly beneficial for individuals with limited range of motion, as it ensures comfortable and efficient operation of the OHMni-Stick.

  In comparison to other "low force" joysticks on the market, the OHMni-Stick outperforms them significantly. While some devices advertise force requirements of 8 grams, 10 grams, 40 grams, or more, the OHMni-Stick sets a new standard by reliably measuring forces as low as a single gram. Additionally, it surpasses these devices in terms of displacement as well, with precise control achieved using a mere 0.2mm of movement.

  It's worth noting that a standard wheelchair joystick typically requires an operation force of about 200 to 250 grams, further highlighting the advantage of the OHMni-Stick's low force requirements.

  These objective measurements demonstrate the remarkable sensitivity of the OHMni-Stick and its potential to significantly improve the daily lives of individuals with limited muscle strength and restricted range of motion. By providing effortless control and reducing physical exertion, the OHMni-Stick empowers users, promoting independence and accessibility.

• Modular Grips

  oneohm • 05/26/2023 at 21:30 • 0 comments

  I'm excited to provide a project update that highlights the modular, swappable grips for the OHMni-Stick. This addition allows for easy interchangeability of grips based on the user's abilities and preferences, offering a personalized and adaptable experience. Let's explore the reasoning behind this design and the advantages it brings:

  The primary motivation for incorporating modular, swappable grips is to cater to the diverse needs of users with varying abilities. By providing multiple grip options, the OHMni-Stick becomes more inclusive and versatile, accommodating individuals with different levels of dexterity, muscle strength, and comfort requirements. Users can simply swap out grips based on their specific needs, ensuring a customized and ergonomic interface.

  The grip-swapping mechanism relies on three powerful magnets that securely hold the grip onto a "push-plate." These magnets are carefully chosen to ensure a robust attachment during normal use. However, they are also designed to reliably detach the grip in the event of an impact, muscle spasm, or any other sudden force that exceeds the maximum rating of the load cells. This safety feature prevents any potential harm to the user or damage to the device.

  The advantages of the modular, swappable grip system are significant. First and foremost, it allows users to tailor the OHMni-Stick to their individual needs and abilities, promoting a sense of control and empowerment. Whether someone prefers a more traditional power chair-style grip, a puck-shaped grip for easy palm control, or a "saddle-style" grip that helps securely hold the user's hand in position, the OHMni-Stick can accommodate their preference. This modularity also allows for future expansion and innovation, as new grip designs can be developed and integrated into the system, keeping the OHMni-Stick up to date with evolving user needs and technology advancements.

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