Relays as switching devices
Problem: The signal output of a small reed is too weak to switch a DC-motor. Solution: Using a relay!
Functioning of a relay:
Relays are electromechanical devices consisting of an electromagnet und some contacts. The switching mechanism is carried out when the electromagnet is under voltage – that means the relay is “activated”.
Relay are mainly used when a low-power signal has to control a circuit with high power.
Advantages of a relay compared with electronic switches:
- Galvanic isolation (if you don´t use an opto-coupler)
- Higher switching capacity
- Low switching frequency
- Mechanical switching means wearing
Relay for memory functions within the control circuit
Problem: The memory function of the valve is lost with the spring reset.
Solution: The memory function must now be carried on the control side, i.e. the electrical circuit. The solution is a so-called latching relay: