USB to AA converter?
Basically, I want to power a small AA device from a usb port, preferably terminating in something that will fit snugly into the two-AA receptacle. I searched the archives, but couldn't find an equivalent project. Any assistance would be appreciated. Thanks.
Discussions
2 years ago
You can use a 3.3V voltage regulator, the additional 0.3V won't be a problem if you check the voltage of fresh batteries.
Problem is the available power.
A standard USB port supplies a max of 500mA and some computers have no real protection for them.
So to get both you might want to consider adding a 10Ohm resistor between USB and regulator to limit the max current.
If you go for SMD parts there will be no problem with size either in these power ranges.
Depending on the type of regulator and device requirements you might want to follow the recommendation in the data sheet for additional capacitors to stabilize the output.
In case the additional 0.3V are a problem you can add a diode with a similar voltage drop into the output line.
2 years ago
USB is 5v. 2 AA batteries will be 3v.