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I am working on a part of a project for a university exam and it includes an interface with a touch screen.

The touch screen is a classic resistive four wire, it comes with a display of course. Datasheet is here.

We've chosen the TSC2003-Q1 from texas instruments, it basically is a SAR adc that can also drive the resistive sheets, we've made the board and all seems to work but I'm having huge issues connecting the touch panel to the board.

The wire coming from the panel is a sort of FPC, you can see it in this photo: fpc from display

So I've promptly chosen a ZIF FPC connector from molex, as per next photo: connector board

The problem is that the "wire" coming from the panel is not exactly an FPC: they are usually made of plastic and the contacts are copper or some other metal that is chemically deposited on the plastic substrate, but this is different. The contacts seem to be of graphite or something similar and they're very weak, and here comes the problem. I've been very careful inserting and removing the fpc in the connector but the graphite has been scraped away by the contacts, in the first picture you can see clear spots on the dark grey strips, these are NOT metal strips but is the underlying plastic.

So here comes my question: what connector is suitable for this particular type of wire? Soldering is impossible, the plastic melts and the graphite messes up. Connecting another kind of wire to the screen is impossible too, the resistive sheets are part of the cable itself and the traces seems to be just "painted" with some sort of conductive material, just like the tip of the FPC.

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  • \$\begingroup\$ I have used this kind of interface to a keypad. The thing is we only connected it once, during assembly. Connector interfaces are made for specific purposes. I think these are really on the low end of the "operating lifetime mating cycles scale". \$\endgroup\$ – Dejvid_no1 Apr 8 '14 at 11:27
  • \$\begingroup\$ That's what I thought. The problem is that it is quite useful to connect and disconnect the whole thing since I need to bring it to class where we use another FPGA, and this whole thing is still in testing... I think I'll just live with it then. \$\endgroup\$ – Vladimir Cravero Apr 8 '14 at 11:33
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I think you have the right type of connector but the wrong type of connector interface for your application. If you really need to attach/detach the panel you could make yet another connector interface board with a more durable connector.

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  • \$\begingroup\$ So your suggestion is to stick a connector to the cable and then solder a pcb or some wires to this connector in order to never have to disconnect the touch screen again, correct? \$\endgroup\$ – Vladimir Cravero Apr 8 '14 at 11:34
  • \$\begingroup\$ Yeah, sort of: ZIF on on small PCB. The PCB has another more durable connector which attaches to your CPU-experimientboard-whatever. \$\endgroup\$ – Dejvid_no1 Apr 8 '14 at 11:45
  • \$\begingroup\$ The term I heard for this arrangement is a 'connector saver'. A second connector is used to avoid cycling the first one. In it purest form your 'other' interface would be of the same type (flat cable) but more durable. \$\endgroup\$ – Wouter van Ooijen Apr 8 '14 at 21:12
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I think you need something like this: http://www.adafruit.com/blog/2011/02/10/new-product-touch-screen-breakout-board-0-5mm-fpc/

... to which you would attach a pin header or plug, and the mating one on your big PCB.

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  • \$\begingroup\$ Yeah I can make one of those actually... I think I'll just cut the fpc, insert it and never remove it again and live with it. \$\endgroup\$ – Vladimir Cravero Apr 8 '14 at 11:43
  • \$\begingroup\$ looks great for this application! \$\endgroup\$ – Dejvid_no1 Apr 8 '14 at 11:49
  • \$\begingroup\$ @Dejvid_no1: Ain't google great! \$\endgroup\$ – gwideman Apr 8 '14 at 11:52

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