Using USB Power Input on Project Board

I'm hacking a toaster for my wife to play a song when the toast is done (my nephew will get a farting toaster). I was wanting to use a wall wart transformer to get the 5V output. The Project Board spec sheet says it can accept 2.4V - 5.5V but when I use 5.0V the PWM nor DAC SPKR work. If I use a battery pack (3.0V) it plays fine. Can I do anything to get the audio on the project board to work with USB power input?

Hey, wjwhf:

You are correct - the spec sheet for the Project Board says the maximum input voltage is 5.5V. This appears to not be accurate, though. The Sonix chip on the board works up to 5.5V, which is why we may have spec'd the entire Project Board up to 5.5V. However, the flash memory on the board is NOT spec'd up to 5.0V. (This is an oversight on our part.) If 5.0V is not working for you, but 3.0V is, then I suspect it's because the flash memory is not working at 5.0V.

We run the Project Boards on three AA or AAA batteries all the time (4.5V), so we know this works. It may be that 5.0V is just too high for the flash memory.

The simplest fix is to put a diode in line with your 5.0V supply. So 5.0V from your USB would go through the diode and then to the Project Board. This will have the effect of dropping the USB voltage by 0.6V or so, resulting in 4.4V (or so) being applied to the Project Board.

If you need any other clarity on this issue, please let us know. Sorry for any confusion.

- Will @ Foxonix