Hi guys,

I've built a portable boombox that runs off 3 AA Batteries. I built it to take away camping with me as batteries are the best option. However the project turned out really well and sounds great, so I wouldn't mind using it around the house or in the shed etc... but I would want to run it off mains whilst at home.

Using an old usb charger from a phone and a usb cable should work fine as the amplifier can take a maximum voltage of 5.5v.

What I want to be able to do is run the boombox on mains without having to disconnect the batteries or have to add a separate switch for them. What do I need to do to be able to just plug in the usb cable and have power without worrying about over voltage from two sources and also damaging the batteries?

I thank you in advance for your responses.

Cheers,
Loggio

 

Add a power jack like this.

It has a set of contacts built in that disconnect the batteries when the mating plug is inserted. Of course that means that you have to change the plug on the mains adapter to one of these.

 

Or put a manual DPST changeover switch, to select which of the 2 power sources the amp runs from.