Diagram of a simple time bomb in the form of a pipe bomb
The explosive charge is the main component of any bomb, and makes up most of the size and weight of it. It is the damaging element of the bomb (along with any fragments or shrapnel the explosion might produce with its container or neighboring objects). The explosive charge is detonated by a detonator.
A time bomb's timing mechanism may be professionally manufactured, either separately or as part of the device, or it may be improvised from an ordinary household timer such as a wind-up alarm clock, wrist watch, digital kitchen timer, or notebook computer. The timer can be programmed to count up or count down (usually the latter; as the bomb detonates when the time runs out).