Funded! This project was successfully funded on May 31, 2012.

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A pressure sensitive stylus for iPad and Android tablets. Inexpensive to produce and buy, all designs and software will be open source.

THE PROBLEM

Professional artists and interested amateurs love to use their iPads to draw and sketch ideas, take notes, and produce original artwork. Even the best stylus currently on the market has the limitation that it can only present a single level of pressure to the tablet — drawing is either on or off. To mimic variable pressure, a number of software tricks have been developed, but none realistically reproduce natural media or the direct feedback of a pressure-sensitive stylus.

In addition to the iPad, there are a growing number of excellent Android tablets that could benefit from pressure sensitivity. Integrated active digitizers exist, based mainly on proprietary Wacom technology, built into the tablet itself.

THE SOLUTION

By integrating a pressure sensor and physical feedback into a comfortable package, the PressurePen pressure sensitive stylus effectively adds a third dimension to input on iPads and other tablets. This pressure information is sent to the tablet, in the current version, via an audio cable to the microphone port. A small piece of software, which can be easily integrated into an existing application, reads the pressure and translates that into, for example, the width of a virtual paintbrush, density of color, stroke width, etc.

By implementing pressure sensitivity in the stylus, rather than rely on an active digitizer in the tablet, the PressurePen can be used on any tablet with a microphone or headset jack and supporting software, and be easily moved from one device to another.

WHAT DOES IT DO?

The PressurePen sends a signal to the tablet it's connected to that varies depending on how hard you're pressing on the tip. Software on the tablet can interpret the pressure as any sort of third dimension information. For a drawing app, this would most likely change the width or density of the drawing stroke. A light touch renders a fine line, a harder stroke creates a bolder one. Another potential application is gaming and entertainment apps. The harder you press on the stylus could change the speed a character runs, for example.

DIDN'T I JUST SEE A SIMILAR PRODUCT ON KICKSTARTER?

Yes. I have terrible timing. Kickstarter was going to be my first stop once I had a working prototype, but I was put in contact with a potential investor and manufacturer last year who ultimately backed out. This set me back by about six months, and in that time the jaja project had stolen my thunder as "first" pressure-sensitive iPad stylus. 

Or, maybe you mean my previous, more ambitious funding attempt. That one failed. This time, I'm asking for considerably less money, and have more realistic goals for the use of the funds.

WHY SUPPORT PRESSUREPEN?

First of all, you would be supporting open source development — both the hardware and software for PressurePen will be open source. The pressure sensing code will be released under an open license, and the schematics, circuit diagrams and 3D parts files will be available to anyone who wants to make or modify their own. My hope is that this will encourage more creative applications, improvements and compatible add-ons to future versions of the PressurePen.

Ultimately, the PressurePen will be a retail product, and it will work with a number of drawing, sketching and painting applications. If you like to draw or doodle on your iPad or Android tablet, you'll probably want a PressurePen or one of the other pressure sensitive stylus products on the market.

WHY SUPPORT PRESSUREPEN INSTEAD OF BUYING A JAJA OR JOT?

Let me be clear: I'm happy that there are multiple pressure sensitive styluses (styli?) on the market now, or will be soon. When I first conceived of the PressurePen, it wasn't as an entrepreneur or inventor, but because I wanted to draw on my iPad. If the other devices had come to market a year ago, I wouldn't have bothered to teach myself about PCB design, ICs, 3D printing or venture capital.

As for the competition...

The jaja (see their Kickstarter page or official site) looks like a really nice product. Their ultrasonic technology is a real innovation, and thus protected by patents. The complexity of their initial offering means it's hard to know if there will end up being interference problems with ambient noise or other real-world issues, though I'm excited to see it working. The street price is $89.99.

The Jot Touch (see the Adonit site) uses Bluetooth for communication, which makes it untethered and a pretty slick combination of hardware and software. A Bluetooth connection, however, means a battery drain on both the stylus and tablet — they're estimating 12 hours between charges — and makes the device expensive to produce — estimating $100 street price. There's also the hassle of pairing devices and using it on an airplane (no Bluetooth in "airplane mode"). Unfortunately, it's not available yet either, so I can't attest to any specifics. They also claim only about 200 levels of sensitivity.

The PressurePen, in contrast, is a very simple device that should be inexpensive to produce. It doesn't rely on battery-draining Bluetooth or an integrated rechargeable battery, but will run on a single AAA for hundreds of hours. Keep reading for more features and reasons.

WHAT FABULOUS REWARDS ARE YOU GIVING AWAY?

In addition to one of the first short run of PressurePens, there are several other rewards to be had.

There's also a "hacker edition" PressurePen kit that includes all the parts and instructions to build your own, minus the plastic shell. This is intended for those hackers and tinkerers with access to a 3D printer or shapeways.com, and have some soldering skills.

Finally, there are "dumb" styli as well. These are the side product of experiments on different tips for the PressurePen, and have the same chisel shaped silicone tip. The shafts of these are made from your choice of 1/4'' brass, aluminum or steel.

SHUT UP AND TAKE MY MONEY!

Absolutely. I'm actively looking for manufacturing partners at the moment to produce the retail version of the PressurePen. If you have deep pockets or happen to own an injection molding facility, please shoot me an email. Otherwise, choose your reward level. Operators are standing by...

HOW DOES IT WORK?

Magic!

Actually, it's a pretty simple process, and hardly a secret. If you're a developer, and you're interested in adding support to your app, I'll give you a complete tour of the technology as well as sample code for both iOS and Android. Otherwise, be patient, and I'll release all the code and design files online.

HOW MANY LEVELS OF PRESSURE?

From my testing, and based on the way the software works, I'm confident in saying the PressurePen has a resolution of 1,000 levels.

This is actually pretty hard to determine, since it's a matter of an analog process being translated into digital variables. The variation in signal from the PressurePen to the tablet is what determines the pressure reading, and the resolution (number of decimal places) will vary on the tablet's (and its OS's) ability to resolve the microphone signal. 

That being said, based on my testing (current beta prototypes on an original iPad), it can reliably produce 1,000 levels of sensitivity, if not more.

WHY TETHERED? WHY NOT WIRELESS?

While the current generation is tethered to the audio port on the iPad, none of the testers have found that to be a limitation. The cable is very thin and flexible, and doesn't bind or get in the way. Also, it's the easiest way to get a signal into the iPad without having to run the gauntlet of Apple's MFI (Made for iPhone) licensing program. Anything that connects to the dock connector or via Bluetooth has to be signed and licensed by Apple, a tedious and complex proposition. That just wasn't in the cards for an individual hacker like me with no budget and no experience in IP law. Future versions will likely be wireless, though that will drive up the price and complexity. 

If you think the cable will bother you, order a jaja. Honestly, it looks like a great product, and the way it works is impressive.

DOES IT COME IN COLORS?

Seriously? You're asking about colors? Fine: Yes. Ultimately, the retail product will come in all sorts of fashion colors. For now, though, if you choose a current generation PressurePen as a reward, you can have any color you like, as long as it's white. That's the color of the SLA 3D printed parts.

If you have access to a 3D printer or want to order a shell on Shapeways, choose the kit reward, and you can make your own shell in whatever color you can print.

IS IT PATENTED?

Yep. Patent pending, anyway.

WTF? I THOUGHT YOU SAID IT WAS GOING TO BE OPEN SOURCE?

That's the plan. When the PressurePen goes on sale, it will include a complete set of schematics and circuit diagrams for hackers and tinkerers to modify and improve upon. And, if you have access to a 3D printer, the STL files for the shell and other plastic parts will be available.

What little protection the patent provides will be used only to prevent anyone making a non-open product based on the technology.

DO YOU HAVE A WEBSITE?

Yes. I'll be posting more information and photos on pressurepen.net as well as the PressurePen Facebook page.

FAQ

  • App support is still in progress. There is currently a demo app on the iTunes store (http://itunes.apple.com/us/app/pressurepaint/id515016023 ) and I'm in contact with a handful of developers that would like to incorporate pressure sensitivity into their notebook and sketching apps. If you have a favorite app to draw in, be sure to contact the developer (there's usually a support link in the App Store) and ask if they would consider adding support.

    I expect that at least a few apps will be available when PressurePen units make their way into supporters' hands. Watch the updates page for announcements.

    If you're a developer yourself, send me a message, and I'll provide you the latest source for the demo app to take a look at, and build into your own project.

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  • Yes. You will need to be able to solder to assemble the $30 kit. All the components are through-hole, though, so there's no surface mount soldering necessary. As a reminder - you will also have to provide your own shell (STL files for 3D printers or Shapeways are coming soon).

    Last updated:
  • Please add $15 for shipping outside the US.

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  • If you plan to write in your blog or other publication about the PressurePen, or if you're an app developer that wants to incorporate pressure sensitivity into your app, send me a message. I'll be glad to send review units, once the first full batch is produced.

    All review units will be marked as such, and are not for resale.

    Last updated:
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    A tweet of eternal gratitude to the twitter account of your choice.

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    One chisel tip stylus in your choice of bronze, aluminum or steel. This normal "dumb" stylus isn't pressure sensitive, but it has the same tip as the PressurePen.

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    PressurePen "Hacker Edition" - all the components to build your own fully functioning PressurePen, but no shell. You can print your own with a 3D printer, or order a shell at Shapeways in your choice of color and material.

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    One customized PressurePen, three replacement tips, plus your portrait, created with a PressurePen by painter Robert Mars. See http://robertmars.com/

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