[Chris] just posted his latest tutorial which shows you how to read position data from a resistive touchscreen. These devices are fairly simple, and since they’re used in a lot of consumer electronics you can pick one up for a few bucks. This looks like it is overstock for an old Palm device.
The interface is simple, there’s just four conductors on the tab at the top of the overlay. But connecting to these is a bit of an issue since you can’t really solder directly to them. [Chris] ended up using scotch-tape to hold wires in place, with a paperclip to keep them presses against the conductors. Those conductors are used in pairs, with a positive and negative lead for the X and Y axis. To take a measurement you use I/O pins to connect voltage and ground, then read the voltage that makes it to the gound side using an ADC. This works because the point that’s being pressed on the screen acts as a variable resistor for the circuit. Data for the two axes must be read in separate operations so that the positive voltages don’t interfere with each other.
The nice thing is that once you’ve got it working with a small screen it is easily scaled up. In fact, the 23″ touchscreen used on this Android hack is just another 4-wire resistive device.
You can see a video demonstration of [Chris’] test rig embedded after the break.
Continue reading “The basics of reading data from resistive touchscreens”
It’s not that touchscreen keyboards are horrible, but it’s nearly impossible to touch type on an iPad or other tablet keyboard. A team at the Media Computing Group at Aachen University figured out how to put a series of electromagnets underneath a display to provide haptic feedback for touchscreens. They showed off their tech at the 2011 UIST conference and made their paper available.
For the FingerFlux, as the team likes to call it, a bed of tiny electromagnets is placed underneath a panel display. The user wears a ‘thimble’ with an attached permanent magnet. Driving the bed of electromagnets slightly moves the magnet and provides a little bit of sensation to the user.
The FingerFlux can be used to provide haptic feedback like a keyboard. The system can also be used to model constraints – making sure that users don’t move outside the controls they operate, and can guide the user to the desired button.
A bed of electromagnets would be a welcome addition to tablets, if only to prevent typung luje rhus. Check out the demo of the FingerFlux after the break.
Thanks go to [John] for sending this one in.
Continue reading “Tactile computer interface with electromagnets”
If you’re looking to build a really big Android tablet the trick is not to start from scratch. [Peter] pulled off a 23″ Android Tablet hack using a collection of easily acquired parts, leaving the hard work up to hardware that was designed to do it.
He didn’t really build a tablet, as much as he built a big touch-screen add-on for one. He already had a couple of inexpensive tablets on hand to play around with. One of them has an HDMI out port, which let him easily push the display onto a 23″ monitor. He knew the tablet was a 4-wire resistive touchscreen, but he didn’t know if other touchscreens with the same number of connectors and be directly swapped and still work. To test this, he cracked open a second tablet device and connected its touchscreen to the first one’s hardware. When he was met with success it was time to source a couple of 23″ touchscreen overlays to test with the external monitor. As you can see in the clip after the break, it works like a charm!
[Peter] was inspired to write about his experiences after seeing the 23″ Android tablet video in our recent links post.
Continue reading “How to build a 23″ Android tablet”
Fanboys may be in shock from seeing duct tape applied to the screen of an iPad, but we can assure you it’s in the name of science. [Michael Knuepfel] is working on his thesis for the ITP graduate program at the Tisch School for the Arts. He managed to augment the usability of touchscreen devices by adding hardware to them.
What he’s come up with are devices for both input and output. The output devices generally rely on light and color of light displayed on the screen itself which is picked up by a light sensor. The input devices use conductive material to complete a path between your hand and your screen. This lets the capacitive sensing screen detect the presence of your hand, through the conductor. Some of his example devices include gaming controller overlays, encoder rings, and multiple stylus designs.
After the break we’ve embedded [Michael’s] teaser trailer which jumps through several demonstrations. It’s plenty to get your mind rolling, but if you want to know more you must watch his thesis presentation. It’s available as an MP4 download on this page. Just search for his name, [Michael Knuepfel] for the proper link.
Continue reading “Extending the usability of touchscreens”
[Sprite_TM] was cleaning up his hacking workbench when he came across an all-in-one device that had seen better days. After a bit of consideration he decided to tear down the scanner portion of the device and ended up turning it into a multi-touch display.
The scanner relies on a long PCB with a line CCD sensor. This sensor is read in a similar way that information is passed along a shift register. Tell it to take a reading, and then start a clock signal to pulse out each analog value from the pixels of the sensor. In order to scan color images it uses multicolored LEDs to take different readings under different illumination.
[Sprite_TM] takes advantage of this functionality to turn it into a multitouch sensor. The sensor board itself is mounted below an LCD display along with a shield with a slit in it to help filter out ambient light. Above the screen a series of LEDs shine down on the sensor. When you break the beams with your finger it casts a series of shadows which are picked up by the sensor and processed in software. Watch the clip after the break to see it for yourself. It has no problem detecting and tracking multiple contact points.
Continue reading “Converting a scanner into a touchscreen”
Adding touch screen capabilities to your computer is really not very expensive, but it’s a huge amount of work to get everything looking the way that it should. [Deadbird] wrote up a step-by-step guide that will help you install touch screen hardware and get your netbook put back together just like new.
The hardware comes in two parts. There’s the transparent film that covers the screen and the driver board that reads the inputs. The film itself has an adhesive layer on the back that sticks to the LCD panel. But to install it you first must remove the panel from the bezel. You’re also going to need a place to house the driver board. [Deadbird] somehow found enough room inside the case for the controller, but he had to remove the keyboard and motherboard to set it in place. This translates to a complete disassembly of your eeePC. But if you’re used to touch-sensitive devices, and have ever found yourself touching an LCD monitor and wondering why the computer is not following the link, this may be worth it to you. You can see the final product in a clip after the break.
Continue reading “eeePC touchscreen retrofit”
[Enigma-penguin] built a tablet computer out of a Core2Duo Macbook circa 2007. The battery exploded, damaging the case and a few components inside. But there was hope for a new life as a tablet computer. He removed the screen and tested to make sure the computer would still function without it by using the video out port.
Putting the whole thing back together as a tablet proved to have some headaches. He worked through problems caused by the addition of a touchscreen between the LCD and the bezel and made the connections work with the screen flipped. The finished product looks so good because the bezel has not been turned around like on other tablet builds. Instead, a viewing window was cut in what would have been the case behind the screen.
There’s a little more to be done yet. The black USB cable seen above is the connector for the touchscreen which he plans to internalize. The magnetic sleep sensor has been relocated to the headphone jack. Inserting a plug (no cord necessary) puts it to sleep for transport. There’s also an on screen keyboard and the ability to change the screen orientation from landscape to portrait. After the break we’ve embedded one of [Enigma-penguin’s] demonstrations. Continue reading “Mac tablet keeps the look of the donor-Macbook”