ELEC 255 Lecture Notes - Lecture 7: Switch, Sound, Electromagnet
Document Summary
A relay is an electrical switch that uses an electromagnet to move the switch from the off to on position instead of moving the switch manually. When current passes through the coil it creates a magnetic field that pulls the switch close. Timers provide simple time-based control with multiple modes and adjustable timing ranges, discrete outputs and a mechanical or electronic display. They work in on delay or off delay modes. On delay relay: with no contacts it will wait 5 seconds before closing its contacts. When the relay is de-energized, the contacts will open immediately. Can count numbers of parts, procedures and cycles. They can also trigger some process or sequence if the predetermined number of events has happened. They either count up or count down. Devices used to provide information on the presence or absence of an object. Operate on the principles of electromagnetic fields.
