情境
A 24Vdc motor start/stop interface uses a PNP transistor and START pushbutton to energize two relay coils; K1 seals the START command while K2 drives an NPN transistor that switches the contactor coil.
這張圖裡有什麼
看懂背後的決策。
01
K1 seal contact is wired across the START pushbutton to latch the run command until STOP opens the coil path
02
K2 NO contact supplies Q2 base current through R3, keeping the NPN contactor driver isolated from the relay coil circuit
03
D1 across the K3 contactor coil clamps inductive kickback and protects Q2
Use this wiring when converting a 24Vdc PNP start/stop input into an NPN low-side output for a motor contactor in a control panel.