Remove the screw or screws on the control panel lid that is on the side or bottom of the motion detector light -- use a Phillips screwdriver to do this. Rotate the sensitivity knob fully counterclockwise. Repeat this procedure with the timer knob. Place the "Dusk/Day" selector switch to the "Off" position. Close the control panel lid once the floodlight turns itself off. Reattach the screw or screws.
Trip the circuit breaker in the fuse box that is supplying power to the motion detector light's floodlight to turn it off.
Put on work gloves. Unscrew the floodlight from the bulb socket on the motion detector light. Place the floodlight aside so that it can cool off.
Open the battery compartment lid of a battery-powered motion detector light -- if a screw holds the lid down, remove the screw with a Phillips screwdriver. Remove the battery that supplies the detector with illumination power. Close the lid, and reattach the screw if one is present.