# Capacitive Touchscreen for DIY usage?

Anyone know of a good source for capacitive touchscreens in low quantity at a reasonable price? Just something to play around with in projects, I'm interested in either small (eg for portable applications, 3-5") or large (eg for kiosk or standalone applications, 10-20"). I know I can get a resistive touchscreen for pennies these days, but I want a capacitive one (for various reasons).

EDIT: The reasons I'm interested in are basically just the main reasons people use capacitive screens in general. Things like more durable (a solid piece of glass instead of a flexible piece of plastic), Multitouch capable, etc.

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## locked by Dave Tweed♦Nov 23 '14 at 16:53

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I'm just curious, but why do you specifically want a capacitive one? –  edebill Nov 7 '09 at 14:12
Thanks for the helpful answers everyone...I'd up-rank you, but new users have like a zillion restrictions on here. –  davr Nov 9 '09 at 19:26
@edebill - Multi-touch, I would assume. Also, the fact that they are MUCH nicer feeling than resistive screens. –  Connor Wolf Sep 25 '11 at 11:23

I've also found that capacitive screens are hard to come by if you're not an OEM. This 2009 article states "With prices of projective capacitive touch panels at about $2.50-3.00 per inch, the average cost for a touch panel module will be about$30 for a mainstream-size netbook". That, of course, is the price for Asus to buy 100,000 of them, not for you and me to tinker.

Fortunately, there are a lot of OEMs who produce products with capacitive screens, and there is a significant market for replacement screens. I'd recommend that you find a screen (Both LCD and touch panel) which meets your needs on an existing product (whether it's a touchscreen PC, netbook, or PDA) and then try to find a replacement screen for it. While you're looking, take a look at this comparison of the Nexus One, Droid Eris, Motorola Droid, and iPhone touchscreens, to help you decide what to get. Also look for hardware hacking forums for more help, as the datasheets will be hard to come by.

For an example screen, Sparkfun sells the replacement iPhone touchscreen and display for $140 - Not bad for the display, but a lot if you just want the sensor. Directfix (and many others) sell just the digitizer for about$30, some sell the digitizer, glass, and home button for about $50 - you'll have to look around. (Look here - iPAD touchscreen! So long, joystick buttons; hello, 10" glass touchscreen.) Calamari over at Sparkfun said (Concerning the iPhone replacement touchscreen): As you can see in the photos, there are two B2B connectors. On one is for the video. It has a 1v8 SPI bus to configure the controller and a MPL interface for the pixels. You can drive the latter with a LM2506 and that's fairly straightforward to implement although the part is a leadless LLP in its largest incarnation. That interface gives you 18bit color. The second B2B connector is to the touch screen controller. Also 1v8 SPI. During initialization, the touchscreen and host exchange packets of about 80K bytes which tends to rule out using a smaller microcontroller. During a touch, the touchscreen will generate an interrupt every 16ms.The host reads 8 bytes which include the length of the payload packet. The payload is 55 bytes for one finger, 83 for two, etc, and has a simple checksum. On the iPhone, the host runs it at a bit clock of 12 Mhz, but I imagine slower would be fine. As others have said, capacitive touchscreens, while nice, are much harder to work with than resistive ones. Budget some space on your micro (ARM9 or better, probably - Can you handle 1024x768 data at 100Hz?) and PCB accordingly; don't expect to build an iPhone with your Arduino. - Lots of good info here. However they shouldn't be that much harder to work with...just because I have a 1024x768 touch digitizer, doesn't mean I need a 1024x768 LCD behind it. They are two separate issues. – davr Aug 26 '10 at 18:17 @davr, I agree with your statement that LCD and touchscreen resolutions are unrelated, but that doesn't mean they're easy. Quoting my post: "During initialization, the touchscreen and host exchange packets of about 80K bytes which tends to rule out using a smaller microcontroller." 80K ~= 1024 * 768 – Kevin Vermeer Aug 29 '10 at 2:04 The size calculation is wrong, touch controllers won't report more that row I/O times column I/O nodes of data. So even on large screens which may only be 100 total I/O with a byte or two of data per node it would be less than 5K. Smaller screens are much closer to 30-50 I/O and so it is not unreasonable to get the full image in less than 500 bytes. In normal operation, the only information exchange is touch position which is generally X and Y with a strength of signal per touch. Even with a header this is generally << 255 bytes. – naven87 Nov 22 '12 at 7:37 A basic search turned up a couple of companies offering touch screen kits, but almost all are resistive. I think the main reason that the resistive screens are so common is that the control and sense electronics are much harder with the capacitive screens. You can do a resistive screen interface with just the analog input pins of a microcontroller, but for capacitive screens you must have dedicated electronics. Check out this article which runs down a list of development boards and manufacturers http://www.edn.com/blog/1590000759/post/1070050307.html I have sometimes seen touch screens on the surplus market that look like capacitive units: http://www.goldmine-elec-products.com/prodinfo.asp?number=G17048 - Your question is a bit ambiguous, and that makes it hard to answer. What is a reasonable price? Because of the electronics required to control and sense capacitive screens (See jkopel), they are by nature more expensive to deliver a complete product. In my experience, your choices are either pay a good bit for a touch screen ready to go (which sounds like it is outside of your reasonable range) or buy some surplus components (again, see jkopel) and try to figure out all of the particulars yourself. The first way is pricier, the second way is fraught with headaches and does not even guarantee you will be able to use the device. Perhaps you could list the reasons you want a capacitive touch screen? If you did, then perhaps we could suggest alternatives. There are all sorts of methods to do proximity sensing on all sorts of materials for less than a dollar, for example, and if we had a better idea of the kinds of things you are trying to accomplish perhaps we could point you to solutions you would find reasonably priced. - I don't know much about capacitive touch screens but DealExtreme sells ridiculously cheap replacement touchscreens for the nintendo DS. These touchscreens work with an Arduino and connectors and breakout boards can be found at Sparkfun. - Those are resistive 4-wire touch screens. Now, early 2013, you can get them for about 3€/2.50GBP on ebay – Martin H Apr 19 '13 at 12:06 Microchip Pic16707 with mtouch technology can handle capacitive touch screens easily. Its code is free from microchip site. - Hi, but where can I get the touch screen itself from? That is what I am asking. Not asking where to find an IC to work with my touchscreen that I don't have yet. – davr Sep 9 '10 at 17:55 I haven't try this myself. But looking through wacom tablet patent, you could place the sensor behind LCD (between lcd and shield). Therefore it should be possible put Pic16707 sensor board behind lcd. - Can you give me more information on the Pic16707 sensor board? I'm having trouble finding it online. – davr Nov 22 '10 at 22:53 You get it from an aftermarket channel vendor of suitable screens? eBay 'replacement touchscreen' and (for$10 or so) there ya go.

There's more than one way to do it, so it depends on the application. If you want multitouch X, Y, pressure and angle you have a variety of peer patterns among free, ODM, semiconductor and Apple-Copyrighted sensibilities (see the patent search and Apple sites for technical details) to choose among. That is, you could get that info from a resistive plate with five electrodes on it, but interleaved patterns give the tells without processing or generating I/F (which make baseband sync. and antenna reception harder, not that you mentioned those.)

If it has to go over a screen, your selections are narrowed narrowed to Indium Tin Oxide contact networks (under DTFE-polystyrene, ideally) available as replacement screens, and stainless mesh. (There are lots of other ways to do it, but for common processes, those are major points of reference.) See the primer for the Cypress or Bergquist or Analog Devices, or the one matching your phone's API etc. etc. then pick your device at e.g. http://www.goldmine-elec-products.com/products.asp?dept=1039 or of course you may fabricate your own, use eBay, develop contact with Sprint's ODMs in the PRC or India; buy the Solyndra plants and make tubey solar cells that are also performance art touchscreens, whatever.

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