probably just the battery you put in. there is no dimming function. there is a button on the side which changes the warm vs cool color temp. but not for dimming. I use the usb power port now and it's super bright.

you can use the button next to the timer adjustment control to turn it off manually.
but the motion sensor might trigger it right after that. But it will turn off later.

I used the strap for a gift and only tried it out for a short time.
I'm sorry, so I can't help you any further...