Making an ultra-sensitive capacitive iPad Stylus

Thread Starter


Joined Dec 10, 2009
This request is a bit "out there" but hopefully somebody will humour me.

I'm working on a project to automate the testing of some iPad apps that our company is developing. The idea is that a robotic device will sit above the iPad and simulate thousands of user taps.. thus testing the app.

The robot is working reasonably well.. but I'm having problems with the stylus and touch screen. The stylus is a stock capacitive stylus, that I have grounded to a USB ground. This provides a reasonably good stylus response.. BUT.. the stylus pressure required to register a tap is still very high.

The pressure required is so high in fact that many of the robotic taps aren't registering. And if I increase the speed & pressure applied by the servos then the accuracy starts to reduce significantly.

My Question. Is it possible to make an extremely sensitive stylus that would require very little pressure to activate the screen? i.e. only require the slightest touch from the stylus. I don't have any grasp of the physics required to register a "tap" on the iPad touch screen. Something to do with electrical field disruption I believe. The stylus didn't work at all until I grounded it... but even that was trial and error.

Video of Robot in action.

You can see on this video that the robot gives the "Google Maps" icon a good tap, but the app doesn't open. It then gives the "Zoopla" app a really big tap and it does open. But, quite often if I run this exact routine again, neither app will open. A mega-sensitive stylus would be really useful and solve my problems!