Using a switched power barrel jack to select source

[ralusp]

Hi all, I'm prototyping something which could be powered from a 30VDC battery or 24VDC power barrel jack. I'm trying to find the simplest way to take power from the power jack if present, otherwise draw from the battery. It seems like a switched power jack is ideal for this. Whichever source is selected would then feed into a DC/DC converter module that provides a consistent stable rail for the system. These are discrete components connected via wire, not a PCB. All of the components are selected, and I'm trying to ensure I wire it correctly.

I'm confident the center pin of the power barrel goes to the DC/DC VIN terminal, the shell of the barrel goes to the DC/DC GND terminal, and the switch lead for the barrel is attached to the battery return (switch is normal-close). So when a plug is inserted it breaks the battery return's circuit. I'm less sure how to tie the battery positive into the system - I believe it would also be connected to the DC/DC VIN terminal. But should I use a diode? If so, how do I select the right type and parameters? And what's the best way to incorporate one into a wired circuit - just solder a through-hole component inline?

Thanks. 

[SuzyC]

Just use a diode in series with the plus of the 24-V power source, anode of the diode connects to the 24-V source.

Use a barrel connector to apply the 30V power source. When the 30-V power source is connected by the barrel connector the diode will disconnect the 24-V power source. Tie the negatives of the power sources together. For lowest power loss, use a Schottky diode rated a high enough current and voltage handling>40V. For 3-amps 1N5822.

[JustMeHere]

The top left corner of this schematic has an answer.  This is the Sparkfun ESP32 Thing

https://cdn.sparkfun.com/assets/learn_tutorials/5/0/7/esp32-thing-schematic.pdf

[golden_labels]

Using a solid state solution has an important advantage here, compared to mechanical switching. 24 V is enought to cause sparks.

[langwadt]

how much current?

[ralusp]

Thanks for the responses - I'm still digesting the suggestions. System load is 1.5A at 24VDC.

[JustMeHere]

Make sure you consider reverse polarity, and what happens if someone plugs in an AC wall wort.