Delta DVP-ES2/EX2/SS2/SA2/SX2/SE manual Example 2 Start First latched circuit, Stop

1. PLC Concepts

Example 2 - Start First latched circuit

When X1 (START) = ON and X2 (STOP) = OFF, Y1 will be ON and latched. If X2 is turned ON, Y1 remains ON. This is a Start First circuit because START button has the control priority than

STOP

X1 X2

Y1

Y1

Example 3 - Latched circuit of SET and RST

The diagram opposite are latched circuits consist of RST and	Stop first
		X1
SET instructions.
		X2
In PLC processing principle, the instruction close to the end of
	Start first
the program determines the final output status of Y1. Therefore,		X2
if both X1 and X2 are ON, RST which is lower than SET forms a
			X1
Stop First circuit while SET which is lower than RST forms a
Start First circuit.
Example 4 - Power down latched circuit
The auxiliary relay M512 is a latched relay. Once X1 is ON, Y1			X1
retains its status before power down and resumes after power
			X2
up.
		M512

Example 5 - Conditional Control

X1	X3		Y1	X1
Y1				X3
				X2
X2	X4	Y1
			Y2	X4
Y2
				Y1
				Y2

SET Y1

RST Y1

RST Y1

SET Y1

SET M512

RST M512

Y1

Because NO contact Y1 is connected to the circuit of Y2 output, Y1 becomes one of the conditions for enabling Y2, i.e. for turning on Y2, Y1 has to be ON

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