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I am using JST SM connectors for connecting two sets of wire. There are two slots in 2-pin connector. I wish to know, what is general convention for assigning the polarity to these slots? Is it slot 1-ground & slot 2-Vcc or slot 1-Vcc & slot 2-ground? Also how should I assign these slots for control pins(like clk/sw/sck)? Is there any uniform convention? And what is general assignment of slots in case of 3-pin connector? I have attached an image of the connector with visible slot numbers. Any Help is appreciated.

Image attached - JST SM2.5 connector(Male & Female with slot numbers)

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  • \$\begingroup\$ As long as you don't follow a standard, I don't think there is a convention. \$\endgroup\$ – Arsenal Feb 14 '18 at 8:41
  • \$\begingroup\$ I like to put ground at pin 1, but that’s just a personal preference. \$\endgroup\$ – DoxyLover Feb 14 '18 at 9:01
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Surely the standard has already been set by the battery manufacturers? I have many toy 4.8v NiCd battery packs wired with pin 1 Vcc and Pin 2 ground. Using these as stand-alone plugs and sockets there is no problem, but wishing to use one of these pre-wired battery packs, it becomes important.

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  • \$\begingroup\$ If these connectors are already often used for battery packs, the OP may want to consider using something else to avoid confusion. \$\endgroup\$ – duskwuff Feb 24 '18 at 1:27
  • \$\begingroup\$ Thank you for your comment duskwuff... however, one can purchase these connectors already wired (as in the top example) both ways. If the battery manufacturers have chosen a polarity, surely the standard has been set by them? I like this connector for low current applications as they lock shut. I could change the female plug on the battery, but that would render the supplied chargers incorrect. \$\endgroup\$ – David Feb 24 '18 at 1:57
  • \$\begingroup\$ I'm not sure I follow. The OP didn't mention a battery anywhere -- they mentioned that the connector might be used for power, but that could just as easily be 12V as it could 3.7V or 4.8V… \$\endgroup\$ – duskwuff Feb 24 '18 at 2:02
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I spent some time looking too (in my case for a JST XH 2-pin battery connector polarity standard). Did not find any standards/conventions.

  • Batteries from different manufacturers (in my case 1-cell LiPo batteries) use different polarity.
  • Connectors sold separately (with attached wires in the male connector) also use different polarity depending on the manufacturer.

If you are making a PCB, try to indicate in the silkscreen of your board the connector polarity (i.e.: where "+" and "-" go) to make it clear for anybody (and for you when you forget in in the future).

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