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I'm improving a PCB design to be more human-error-resistant, with electrical connectors being directional. For the (24V DC) power supply I want to use the B2P-VH JST connector, which seems to be frequently used for that purpose.

My question is - is there a traditional / customary / best practice polarity of the connector - which pin gets the GND and which gets the VIN?

B2P-VH JST connector

I know I can go either way as long as I provide the power supply as well, but I'm curious if one way is more "professional" than the other.

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    \$\begingroup\$ Flip a coin. What devices frequently use this connector? Which way do they use? \$\endgroup\$
    – Kartman
    Apr 1, 2022 at 14:18
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    \$\begingroup\$ If reverse polarity is a serious concern, consider adding reverse polarity protection to the power input circuitry. \$\endgroup\$
    – vofa
    Apr 1, 2022 at 15:02
  • \$\begingroup\$ My experience is that pin 1 could be anything; there is no standard. \$\endgroup\$
    – rdtsc
    Apr 1, 2022 at 15:12

4 Answers 4

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While JST does a pretty good job of labeling pins on VH connectors, there's no standard polarity like there is for e.g. barrel or XT series. Take a look at these two power supplies from TDK:

CUS60M

CUS200M

The CUS60 uses a 4-pin JST VHR with pins 1 and 2 ground and pins 3 and 4 V+. The CUS200 uses a 6-pin VHR with pins 1-3 V+ and pins 4-6 ground. If you really want to make it bulletproof, you could one or more of the following:

  • Add reverse polarity protection as @vofa said
  • Screenprint the polarity on the board next to the connector
  • Use a 3-pin connector with the center pin ground and end pins V+ (or the other way around)
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Although there is no standard, you may want to do what I do: pin 1 is always ground.

The problem is that pin 1 is not clearly and consistently defined for single-wall wire-to-board connectors (my site) by variour manufacturers.

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There's no way to be sure of the polarity of such connectors. There's no standard of any sort, nor even an informal one.

In series with the input, add a Schottky diode. That way at least the device won't be destroyed if connected in reverse. The diode impedance falls as you parallel them, so you can get fairly low voltage drops (0.15V or so) even at higher currents of several amps if you parallel the diodes.

If you want it to operate correctly with either polarity of supply, use a full Schottky power diode bridge. Parallel the each diode separately to lower its effective impedance and thus voltage drop and power dissipation as needed.

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Davide Andrea suggests using pin 1 as ground. I (and by reflection, my company) does it the other way around. We use Pin 1 as (+).

The reasons for this are historical. In the early days of professional stage lighting controlled by analog signals, pins 1..n were the channel signals and the last pin used was Ground. We extrapolated this to even simple two-pin connectors: Pin 1 is (+), Pin 2 is (-) or Gnd.

Obviously, there are exceptions. Especially when matching existing equipment and connectors.

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