This document provides a diagram and explanation of a three wire start/stop control circuit. When the start button is pressed, current flows through the normally closed stop button and energizes relay coil K1. When coil K1 energizes, it closes contacts K1.1 and K1.2, allowing current to continue flowing through K1.1 to maintain the circuit even after releasing the start button. Current also flows through K1.2 to turn on an indicator lamp. Pressing the stop button opens its normally closed contact, breaking the current to the relay coil and de-energizing the circuit.

1. 1
2
3
1
1
1
2
5
3 4
4
[2,3]
K1
5
Start Stop
K1.1
K1.2
‘On’ Indicator
Lamp
‘Latch’ Contact
Coil
K1
5
K1
5S1 S2
Three wire start/stop control circuit diagram
When the start button is pressed current flows through N/C stop and energises relay coil K1
When coil K1 energises it closes contacts K1.1 and K1.2
Current will now flow through K1.1 providing a parallel path to start button, the start button can know be released and the coil will
stay energised.
The current will flow through K1.2 and turn on the lamp.
When the stop button is pressed this opens the N/C contact and breaks the current path to the relay coil, this in turn opens K1.1
and K1.2 returning the circuit to its de energised state