A relay is an electrically actuated switch. Most use an electromagnet to operate one or more switches. Relays are used where it is necessary to control a circuit by a separate low-power signal, or where several circuits must be controlled by one signal. They were used a lot in telephone exchange and railway applications.
Specifications
Related to the electromagnet:
- Coil voltage (maximum rated voltage to operate the coil, V)
- Coil resistance (resistance, Ω)
Related to the switching contacts
- Maximum switching voltage (V)
- Maximum switching current (A)
Please pay attention to the type and number of contacts.
Advice: When implementing a relay, make sure you always add a small diode over the coil in the reverse direction to eliminate back-EMF generated voltages (flyback diode).