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I was ripping off a Center 352 Infrared Thermometer. The basic functionality is to sense the temperature and display it on an LCD. The LCD turned out to have no interface to the controller. The PCB had 3 LEDs which were focused onto the LCD to provide backlight. Other than that there was no other active component(/connector) that can transmit the data to the LCD. How is this interface done?

I tried googling and tried searching for connectors/interfaces without electrical contact. But, I got no idea how it works.

Attached image 1image 2


marked as duplicate by Dmitry Grigoryev, The Photon, laptop2d, ThreePhaseEel, Daniel Grillo Nov 16 '16 at 21:14

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    \$\begingroup\$ google "zebra strips" \$\endgroup\$ – PlasmaHH Nov 14 '16 at 11:18
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    \$\begingroup\$ Are you sure you mean "ripping off", and not "taking apart"? \$\endgroup\$ – psmears Nov 14 '16 at 12:25
  • \$\begingroup\$ i've seen this on a toy math game too \$\endgroup\$ – user129900 Nov 14 '16 at 15:17
  • \$\begingroup\$ @psmears - I think "stripping down" might be the correct idiomatic translation intended by the OP. \$\endgroup\$ – robinCTS Nov 15 '16 at 2:59
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    \$\begingroup\$ As others note it's a "zebra connector" which conducts through the plane of the rubber but not across it (ie in the directions you'd expect for it to work). Use an Ohm meter to measure resistance through the rubber between directly opposite points and then offset. When the probes are opposite each other there will be a low resistance path. You will find that when the probes are offset by more than the thickness of the conductive bands that the resistance will be very high (or more :-) ). \$\endgroup\$ – Russell McMahon Nov 17 '16 at 7:59

The little piece of rubber you removed IS the connector.

Elastomeric connectors look like a piece of rubber and are commonly called "zebra stripes" because the conductive carbon stripes in the rubber look like zebra stripes when viewed from the end.

Image from Wikipedia:

enter image description here

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    \$\begingroup\$ Could you add why these are used rather than other types of connector? Is it just a question of space? \$\endgroup\$ – Rich Nov 14 '16 at 14:48
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    \$\begingroup\$ The zebra strips are used because the LCD is made of glass, with very fragile (and nearly invisible) infused metal contacts. The strip is flexible and allows easy mechanical mount of fragile glass substrate of LCD. \$\endgroup\$ – Ale..chenski Nov 14 '16 at 15:28
  • \$\begingroup\$ There are other, similar types of anisotropic connectors such as anisotropic adhesive tapes that function in the same manner but have no striping visible, from this PDF "...[A]dhesives randomly loaded with conductive particles. These particles allow interconnection of circuit lines through the adhesive thickness, but are spaced far enough apart for the product to be electrically insulating along the plane of the adhesive." They are also spectacularly expensive per roll. \$\endgroup\$ – Dan Nov 14 '16 at 18:07
  • \$\begingroup\$ @jre The contacts in the pcb is quite big whereas the contacts in the lcd (4 black dots, if I'm right) and comparatively very small, how would the connector(conductive part of connector) stick to the contact during assembly. It seems to be very small. \$\endgroup\$ – seetharaman Nov 14 '16 at 18:15
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    \$\begingroup\$ @seethraman : The four dots you see aren't the connections on the glass. Hold the glass up to the light and you will see the ghosts of the real, metalized connections that are plated on the glass. They are very nearly transparent. \$\endgroup\$ – JRE Nov 14 '16 at 19:35

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