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Battery Powered Speaker, want to add usb power.

ksharp117

Hello All.

I've been working on modding a portable Battery powered speaker I got at a thrift store for cheep. The original speakers where 2 little tweeters (witch sounded awful). The first thing I did was replace the speakers with two RCA cable headers so I could plugin bigger speakers. Witch turned out great, great sound and good volume.

 

There is on last thing I would like to do however. I want the option to plug this in to a USB port for power, to prolong the battery’s for when I need them. I’m not to well versed(but I’m trying to learn) in USB power and Battery power so I have a few questions.

 

      1.The speakers system runs on 3 AAA battery’s. By my logic (witch is probably completely wrong) one battery is 1.5 volts so 3AAA battery = 4.5 volts. USB runs 5 volts, so USB should be able to run the system right? Or is the .5V differences going to cause problems?

 

      2. Is there any major differences between usb power and battery power. Can I just detacth the red and black wires from the batters and                                           splice it to a usb cable?(manly for testing purposes) or is this a no no.

 

     3.Lastly, I’d like to be able to run on battery power until the usb is plugged in, using the usb and bypassing the battery. What would be the   best way to go about this?

 

Sorry, some of these questions may be extremely stupid, But I want to make sure I don’t fry my bored.

I’ll post some pics showing after my mod with the new speakers, and 2 of the circuit board (You’ll be able to see the old speakers in these pics.

Anyway, sorry for the giant post. Thank you all who read this far, I really appertain your time. Anyways, I’ll leave it here, Thanks to all.

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  • 0

    Hi Kabrun - The two voltages are close enough to work ok for your application. Most audio amplifier circuits can tolerate a range of a couple volts so 0.5 volts will not be a problem. You could use a single pole double throw switch to choose between the USB and your batteries.  This type of switch will have 3 connections on the back. When the switch is one direction the center connector is connected to one side and when the switch is toggled to the other side the center is connected to the other connection. To make this work we connect all the negative wires from the battery, USB and Amp together. We run the positive wire from the amp to the center connection of the switch and USB positive to one side and Battery positive to the other side.

    John

  • 0

    Hi Again Kabrun, When you want to add something to your original post it is best to reply to yourself on the original thread. If you put in a new post you will not be able to keep track of what is going on. You may want to delete the second posting and put your extra pictures on a reply to the original post.

    John

  • 0

    Hay Thanks John for your input. Yeah, I didn't mean to post this twice. I think Element 14 has bee having problems with the website, every time I tried to post this the website went down. I guess I got a little clicker happy.

  • 0 in reply to ksharp117

    Hi Kabrun - If you get a switch with a center off position you could eliminate the power switch currently on the amplifier board. In this way you would have batteries on one side, USB on the other and unit OFF in the center. You are correct about the website last night. I couldn't get it to work correctly either. Officially it was down for maintenance. I also forgot to answer your question about whether the electricity from the batteries is dfferent than that from the USB. The amount of current that any voltage source can supply is limited by something called internal resistance. If we connect a device to the supply that demands a lot of current the voltage of that source will be pulled down to a lower voltage. This is why you can not start a car with 8 AAA batteries. In your case the internal resistance of the USB and AAA batteries are similiar and your amplifier doesn't demand that much current anyway. The bottom line is that in this case it should work well to use one or the other.

    John

  • 0 in reply to jw0752

    Thanks John for your input. I was able to get it all wired up and working with your advice.  

     

    Thanks again.