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Posts: 2
Reply with quote  #1 
I got a DIY bug and bought a small FM receiver off of Amazon.
It's not much of a DIY project because really all it needs is an antenna soldered on and mounted in a case.  It has a headphone jack and a USB in.  I thought it would be fun to mount it in an Altoid tin.
I have a question about it, though.  I see that there is a place to solder DC power onto the board.  If I plug USB power into the unit and measure the voltage on the DC IN terminals, it shows 4.5v DC.  It made me think two things.  First, if I solder a battery onto the board, what will happen to it if I plug the unit in to USB power?  An alkaline battery might not like receiving 4.5v from the board.  And second, if instead I soldered a rechargeable battery to the board, would it recharge when the board was plugged in?  Would that be safe?  Would the battery overcharge?  Would there be some other circuit that I could add in to manage charging?
There is no 'off' button on the radio, so if it's going to run on battery power, I'll have to add a micro switch to turn the battery power off when not in use.  I could turn the switch off and isolate the battery when using USB power, but it would be really slick to be able to charge the radio's battery like a cell phone.
I'm really a novice at this sort of thing, but I'm enjoying learning coming along with it.  If you have any thoughts, I'd certainly appreciate them.
Thanks so much,

Posts: 1,905
Reply with quote  #2 
Soldering a battery, either rechargeable or not, and then plugging in to USB will damage the battery and/or the USB port. DO NOT DO IT!

A rechargeable battery needs a 'battery charger' to control the charging - cannot just connect it to power.

Alkaline batteries are not rechargeable so should never be connected to power.

Posts: 2
Reply with quote  #3 
Thank you, Frank.  Any idea if there's some kind of a charge controller circuit that I could add the unit to make this work?  If not, I'll just choose one for the unit and stick to that.
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