I have a Bluetooth board in which I wan to have the option to power it by a battery or power it by a wall adapter. The power input is a 5mm x2.1 mm plug with two wires (positive and negative). I have both a wall charger and battery available (24v). I want to use a 3 way slide switch (on,off,on). One position would power the board using the wall adapter, One position would be completely off and the last position would power it by the battery. but I am not sure what I need to do, how to wire it or what Rating the switch would need to be. I've found some switches but they are rated for a lot higher voltage than 24v. Would that be okay? Any and all information would be great appreciated.

Link to sample switch shown below https://www.amazon.com/gp/aw/d/B008DFYNX4/ref=mp_s_a_1_14?ie=UTF8&qid=1490924981&sr=8-14&pi=AC_SX236_SY340_QL65&keywords=on+off+on+switch+dpdt

Thank you in advance.


1 Answer 1


Are you powering the BT board directly with a 24V supply? Most BT boards/modules cannot handle more than 5V unless there is a regulator on board which converts higher supplies to the appropriate supply voltage. Even then 24V is high. Connecting a 24V supply might fry the board.

That switch would work (though it might be overkill considering its ratings). Something like this would be more suitable and inexpensive. You'll need to tie all the -ve wires together. The BT supply wire (or +ve) will go to the middle pin of the switch, the wall wart +ve and the battery +ve can go on either of the two ends of the switch pins.

  • \$\begingroup\$ Thank you for the help @electrophile Yes the 24v is gong directly to the BT board. It states it can be supplied from 9-25v and does not mention any regulator. I sat fingers the 5 to a 4 in my original post my apologies. The switch you mention looms like it only toggles between the two and doesn't of an all off position, is that correct? If I were to use the switch in the sample link I provided what would the wiring description be? Would the -ves still be ties together? Or would they go on separate posts? \$\endgroup\$ Mar 31, 2017 at 11:27
  • \$\begingroup\$ The switch I had listed has two slide positions and ensures that at any given time either the battery or the power supply are connected to the board. The switch you've listed has three positions. The middle position disconnects the board from either of the supplies and ensures no power reaches the board. Yes all negatives need to be tied together to ensure all supplies have a common reference. Can you post the link to the BT board you have? Also 24V seems to be toward the higher specified limit. You might want to try a 9 or 12V supply and that would work just as fine. \$\endgroup\$ Mar 31, 2017 at 14:28
  • \$\begingroup\$ Thank you again. amazon.com/dp/B06XJ2M2CB?psc=1 \$\endgroup\$ Mar 31, 2017 at 14:39
  • \$\begingroup\$ As for the switch, I would like to have the middle position option. What would be the best wiring scenario for this switch? \$\endgroup\$ Mar 31, 2017 at 15:05
  • \$\begingroup\$ Ah this is an amplifier board. I was under the impression it was purely a BT board. Here is how you would wire it. The switch as two columns (poles) but you can wire any one. \$\endgroup\$ Mar 31, 2017 at 15:47

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