Enginursday: DIY Assistive Technology Mouse
SparkFun's first attempt at creating an inexpensive, accessible, DIY assistive technology mouse.
At SparkFun, there's a good deal of discussion about assistive technologies and how we as a company can contribute to the design and advancement of these devices. With the proliferation of 3D printers and other mechanical rapid prototyping tools, assistive technology is moving more and more into the DIY realm. There are hundreds of groups and companies already working on the varied and complex problems solved by assisted technologies (and you can help!), but there is always room for design improvement of any solution. The more iterations and thought put into a solution, the better the it will be. For this reason, we decided to try our hand at designing a DIY solution to one particular problem: the control of a computer mouse by someone who doesn't have the use of their hands.
One of the existing solutions (among many) to this challenge is a technology called Sip-and-Puff. We used this as the inspiration for our design.
The user controls the device by blowing or sucking air through a tube at specific intervals and forces, which trigger actions. This solution has proven successful, but expensive. A DIY solution is cheaper, and replicable by anyone with a soldering iron and a computer.
As I said before, this is just a design iteration to see what we could do. SparkFun doesn't currently have any plans to start producing and selling assistive devices as such, but if some of our products are well-suited for use in an assistive solution, we want to explore that so we can possibly help others who are planning on producing them. If nothing else, we will have taken a shot at designing another iteration, seeing what works and what doesn't, and learning from it. That being said, here's what we've done so far:
This is our rapid-prototyped, off-the-shelf, super-inexpensive version of the sip-and-puff mouse. It is connected to a computer over USB and registers itself as a mouse. The cursor is controlled by moving the joystick (pen tube) in the direction of the desired motion, and it registers a click when air is blown through the tube. It's not pretty, but it's functional and surprisingly easy to use with a little practice.
The idea is to build something that could potentially have the same functionality as the commercial sip-and-puff controllers, but be totally DIY and cheaper than existing solutions. Manufacturers of assistive technologies are beholden to a lot of red tape: medical-grade components, certifications, testing, etc. DIY'ers can skip that and save a lot of money. Our design constraints for this device were:
- It must be easy to build with readily accessible components
- It must be inexpensive
- It must be open and modifiable by the end user
The guts of our box contain a Teensy 2.0, running the code to register as an HID mouse, an Analog Joystick Breakout, and a BMP180 Pressure Sensor Breakout. The user actuates the joystick to move the mouse, and a click is registered by a change in the air pressure inside the box, detected by the BMP180. As a device, it functions well, but obviously parts of the design need improvement. Specifically:
- The enclosure. A Tupperware box with Stick Tack isn't going to cut it as an enclosure. It's too big, and not rugged enough for extended use.
- Spit. The tube (which in this case is a Bic pen housing) is replaceable, but that doesn't stop saliva from accumulating in the box.
- Alternate mouse functions. So far we have a click. We need to add functionality for scroll, double click, right click, etc.
This is our first bit of exploration. How could we further improve this design, while still adhering to our original constraints? This design rings up to a total of about $35, an order of magnitude cheaper than most off-the-shelf devices with similar functionality. It can be assembled and programmed by a beginner with nothing more specialized than a soldering iron. Are there any ways that we could make this even cheaper and easier?
