how can i power my 3 AAA led flashlight with USB?

i want to power my 3 AAA led flashlight from a usb?
thanks.


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kmossman7 years ago
If your LED flashlight works with rechargeable batteries then it needs only 3 * 1.2 volts (3.6). If it needs normal alkaline batteries then it needs 3*1.5 volts (4.5) Measure the current it takes using a multi-meter or VOM - call that IFL If IFL is much more than 100mA then I suggest dropping the idea - the current needed is too high. You may need a resistor between (say on the V+ side) It's value would ( 5 - 3.6 ) / IFL or ( 5 - 4.5) / IFL depending which battery works best. Example. Alkaline works best, and current is 50mA then (0.5)/50mA = 50 ohms, Use a 47 (or 56) ohm resistor.
Re-design7 years ago
The outside pins are +5 and ground.  Use a meter to determine which is which if you need polarity.  Or look at this pinout if you want to know them all.

The usb port is only good for about half an amp or less so don't use too much or you'll run the risk of loosing your usb port and maybe your motherboard.
100mA, except by negotiation.

Steve
iamsinned06 (author)  steveastrouk7 years ago
this is the flashlight i want to make it a usb flashligt.


IMG_0008.JPG
iamsinned06 (author)  iamsinned067 years ago
it uses 3 AAA battery. so it's 4.5v?
how can i plug it to usb port in my laptop to use it as flash light or a stand light?
MEasure the current the thing draws then.