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,