A shutter release timer is the key part to creating an image sequence that will be turned into a time-lapse video.
There are many versions of timers and they usually come in wired and wireless form. These can be used as a shutter release to take a single image or can be set to take a long exposure with your camera in bulb mode for longer than 30 seconds. These timers are fully programmable and are able to capture everything from 1 second to 99 hours and 99 minuets and every second range in between.
Setting an interval in between photographs will create the image sequence.