STEP8 Self-Holding Circuit


In STEP7, the white lamp is turned on by pressing BS1 (switch 1) and is turned off by releasing the switch. In STEP8, create a circuit so that the lamp is not turned off even when BS1 (switch 1) is released.

Key point

In a “self-holding circuit”, a coil is excited by current externally applied to the electromagnetic relay, an operating circuit is created by the contacts, and the current is kept flowing through the coil.

Devices to use

  • Circuit breaker
  • Red lamp (C2)
  • Fuse (enclosed type, 5 A) 
  • Terminal block
  • Switch 1 (BS1)
  • Electromagnetic relay 1 (R1)
  • White lamp (C9)