I want to use the switch function of a DC-jack to disconnect a load when a battery charger is connected to a battery which powers a constant current source that powers an LED.

Is the wiring shown below the way to do it? Namely, when the charger's plug is plugged in, 3 disconnects and the battery charges, with the load not simultaneously drawing from the battery?



Yes, your schematic is correct.

You may need to test though to make sure that there isn't a momentary short-circuit at any time during insertion. Most will probably connect the charger to the battery prior to opening the switch contact.

  • \$\begingroup\$ Thanks! You suggest: "Most will probably connect the charger to the battery prior to opening the switch contact." But won't the DC plug automatically push away the metal contact 2? There is nothing else users could tamper with, or do I misinterpret what you meant? \$\endgroup\$ – Systembolaget Feb 1 at 14:15
  • \$\begingroup\$ Ah, with "Most..." you are referring to the DC plug and its design/construction, you mean that the outer metal of the plug may make contact with 2 before 3 is mechanically pushed away, right? That won't be good indeed. I am looking to avoid circuitry or a physical switch, hence came to the DC jack switch function. \$\endgroup\$ – Systembolaget Feb 1 at 14:23
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    \$\begingroup\$ Every barrel-type power connector I've seen has a protruding insulator at the front end that pushes the outer contact away from the switched contact before the outside of the barrel makes any electrical contact. They've also all been connected positive side to the pin, so you might want to swap the polarity to keep with the norm if you're using a standard connector. \$\endgroup\$ – Phil G Feb 1 at 14:31
  • \$\begingroup\$ Thanks! Yes, all different DC barrel plugs I bought feature such a protruding piece of plastic. I penciled "check polarity" into my schematic, because all the various chargers here have the polarity standard (and I need the exact opposite here), so I need to put new plugs on. \$\endgroup\$ – Systembolaget Feb 1 at 14:43
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    \$\begingroup\$ Good, then I can always leave the charger plug as it is and don't have to cut it off to change polarity (standard is + on inner, apparently). \$\endgroup\$ – Systembolaget Feb 1 at 16:59

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