I'm trying to connect a microSD card connector to my project (Molex 502774) and am slightly confused by the extra pins (nails?) provided. One of them is marked DETECT NAIL and the other one is SWITCH NAIL. As I understand the DETECT NAIL is for detecting when the card is inside - it is shorted to ground when card is inserted and should be connected to an input with a pull-up resistor.

But what is the SWITCH NAIL for? Does it have anything to do with card hot-swapping?

What is this for?


2 Answers 2


Looking at the drawing, I would guess that DETECT and SWITCH are the two terminals of the switch which detects the presence of an SD-card. This allows for more flexibility in circuit design

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  • \$\begingroup\$ That would make sense. In the notes (top left of drawing) it states that a "detect switch" is closed when card is inserted and open when no card is present. The naming of pins is confusing, though. \$\endgroup\$ Dec 14, 2015 at 13:12
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    \$\begingroup\$ I suggest using a multimeter to test the pins before soldering. If detect and switch are two terminals of the same switch, make sure there is no other conductivity to the shell or other pins first. \$\endgroup\$
    – Passerby
    Dec 14, 2015 at 13:23
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    \$\begingroup\$ This Hirose datasheet supports that theory hirose.co.jp/cataloge_hp/e60900232.pdf \$\endgroup\$
    – Daniel
    Dec 14, 2015 at 17:48
  • \$\begingroup\$ Indeed, but in this one the switch terminals are market clearly - CARD DETECTION SWITCH (A) and CARD DETECTION SWITCH (B), there's even a basic schematic of the switch showing A and B. However this answer is most probably correct, Molex has confused me with their ambiguous terminology. \$\endgroup\$ Dec 17, 2015 at 9:04

Detect_switch is used to turn off the power to the SD card when the SD card is removed - avoiding the short occurring on the VDD supply which might be dragged over the GND damaging the SD card.

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    \$\begingroup\$ Not really. Try examining a card and you will see that the physical design of the card itself avoids that concern, as insertion/removal is in a direction perpendicular to the contact spacing. \$\endgroup\$ Mar 14, 2019 at 16:13
  • \$\begingroup\$ Does it line up a Write Protect feature on the card? \$\endgroup\$
    – CrossRoads
    Mar 14, 2019 at 17:23

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