onboard usb charging for onboard efx

[Jedi Clampett]

For powering onboard effects, I thought it would be good to use usb charging, any thoughts about this?

[Bob Gramann]

I don't know about other issues, but your success depends on your power budget. Will you draw less current than your source can provide?

[Eric Baack]

Might have to use a higher output charger. But yeah check your power budget. Amps in vs amps used

[Peter Wilcox]

What are you planning on charging/powering? If you need 9v you'll need something like this, since usb is rated at 5v: http://www.voltaicsystems.com/usb-9v-boost

[Bob Gramann]

One other thought: I wouldn't expect that some of those usb wall warts would be filtered very well. Your source could be noisy.

[David King]

Depending on the battery type you choose you will need the appropriate charge management circuit in the instrument as well. I'd look at LiPo packs for energy density. There may well be a circuit that integrates a DC-DC converter with the charge management but I couldn't find it. The reason is that DC-DC is not terribly efficient and you only have 500MA from USB to start with so your charging current would be very low, say 120mA at 12V.

Unless your onboard effects can run on 3.7V I'd skip the whole USB idea. For 9V effects I'd be tempted to run 11.1V rather than 7.4V. Just get a universal AC input wallwart charger with the lipo charge circuit built in. If you can run your effects on 3.7V then you have a plethora of cheap USB chargers available to you from places like Sparkfun and Adafruit.

Most batteries make excellent noise filters so you might not need to worry about the noise too much.

[Piotr Sell]

Let me revive this thread to help me understand one thing. I'm myself about to update one instrument I built with a socket (more likely a standard DC jack rather than USB) for charging a standard 9V rechargeable battery that powers the preamp (the way I built it makes getting the battery out a pain). I'm a little pit puzzled about how it should be wired thought. I assume the charging socket should be wired in parallel with the circuit board that given the switching output jack will not be affected by the charging current. Am I understanding this concept correctly?

Moving back to thread related USB charging, I came across "Fishman Universal Battery Pack" that has the mini USB port to charge the li-ion battery and all the circuitry. Looks nifty but I can hardly think of a way I could fit it in my EUB since I don't have a simple electronic cavity back plate there.