I have very limited knowledge of electronics but I am trying to build a battery power USB port for charging. I have a general idea and some schematics skim off this site but I have some questions that I need help on.
I am thinking of hooking on a 9V 2000mAh rechargeable battery to a 7805 to power a female USB port.
1) if I do the above I know the output of the 7805 is 1A and therefore I am assuming that the USB is also going to provide 1A when it's hookup. Am I correct to assume this?
2) I assume if I am charging something that draws 1A then the battery will last about 2 hours. But if I am charging something that need 300mA does the battery last about 2 hours or 6 hours (ball park)?
3) Is there anyway I can restrict the USB to output a max on only 500mA.? What do I need to reduce the power, should it be done before the 7805? Does reducing the power extend the hours of drain I can get from the battery since my equipment needs a max of 500mA.?
Thanks and any advise will be greatly appreciated.
I am thinking of hooking on a 9V 2000mAh rechargeable battery to a 7805 to power a female USB port.
1) if I do the above I know the output of the 7805 is 1A and therefore I am assuming that the USB is also going to provide 1A when it's hookup. Am I correct to assume this?
2) I assume if I am charging something that draws 1A then the battery will last about 2 hours. But if I am charging something that need 300mA does the battery last about 2 hours or 6 hours (ball park)?
3) Is there anyway I can restrict the USB to output a max on only 500mA.? What do I need to reduce the power, should it be done before the 7805? Does reducing the power extend the hours of drain I can get from the battery since my equipment needs a max of 500mA.?
Thanks and any advise will be greatly appreciated.