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I have a PCB design that uses an infrared proximity detector in the form of an IR LED and an IR transistor placed with about 10 mm spacing between them. Now the problem has arisen that I need some sort of physical barrier between them to prevent crosstalk and false proximity detections.

Currently, I'm using the plastic part from male pin headers from which I've removed the actual pins and broken off the a correct length (~ 15 mm). I'm gluing these to the board with super-glue (please don't laugh).

Does anyone know of a surface-mount component that could work as an IR barrier? Obviously I could use the through-hole male pin headers to actually solder on, but I want this board to be able to be automatically manufactured. Any help or advice welcome.

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  • \$\begingroup\$ How about some sort of EM shielding? They make those in fairly substantial sizes. \$\endgroup\$ – Ignacio Vazquez-Abrams Oct 21 '14 at 16:12
  • \$\begingroup\$ Make the PCB manufacturer route out a small piece of FR4 that would slide into a prepared slot. You'd then solder it in the corners. \$\endgroup\$ – Dzarda Oct 21 '14 at 16:33
  • \$\begingroup\$ How high does the barrier need to be? \$\endgroup\$ – Majenko Oct 21 '14 at 16:56
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    \$\begingroup\$ How about an SMD diode, as simply a big hunk of black epoxy that can be installed by a pick & place machine along with everything else? If it needs to be longer, there are SMD connectors. Ultimately though, you might want to look for a sensor module incorporating both the emitter and detector in their own well designed housing? \$\endgroup\$ – Chris Stratton Oct 21 '14 at 16:56
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If there is an extra or manual labor cost for THT 0.1" headers, try SMD 0.1" headers. Pick & Place and wave soldering compatible, but from what I've seen (samtec catalog) these need a minimum of 3 pins due to the alternating smd feet to keep them standing before the solder holds them on.

enter image description here That, or switch to an IR transistor/Diode pair that already comes with a molded body, unless those don't exist in smd (try asking Vishay, they do everything IR).

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  • \$\begingroup\$ Does the opaque plastic holding the pins extend all the way to the board though? \$\endgroup\$ – Ignacio Vazquez-Abrams Oct 21 '14 at 20:08
  • \$\begingroup\$ @ignacio the smd ones, yeah, just about. The female headers even more so. I know samtec has a bunch of options, some standard some not. \$\endgroup\$ – Passerby Oct 21 '14 at 20:13
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Similar to Dzarda's idea, but SMT, you could have a castellated board manufactured that is mounted on an SMT pad.

http://static.sparkfun.com/images/products/RovingNetBlueTooth-01-L.jpg

Alternatively, something like JST's BM-09B connector would be about right, and not too expensive.

enter image description here

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  • \$\begingroup\$ Hmmmm, shouldn't that have been a Canadian Quarter? \$\endgroup\$ – placeholder Nov 21 '14 at 6:41
  • \$\begingroup\$ @placeholder Considering the source of most PCBs, a 1 Yuan coin might have been more appropriate! \$\endgroup\$ – Spehro Pefhany Nov 21 '14 at 12:59

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