Ladder Logic One Shot Rising

OSR - One-Shot Rising

• Triggers a one-time event.
• The OSR instruction is a retentive input instruction that triggers an event to occur only one time. Use the OSR instruction when an event mast start based on change of state of the rung from false to true.
• When the input instruction goes from false to true, the OSR instruction conditions the rung so that the output goes true for one scan. The output goes false and remains false for successive scans until the input makes another false to true transition.

Example 1

In this example we have one button and a light. First time we press on the button the light will go on and the second time we press the button, In other word we want this button to work exactly like a toggle button.

Input / Output

• Switch I:1.0/6
• Light O:2.0/6

Ladder Logic Solution

First Time we push the button.

First Scan: When the push button is pressed the LIGHT_OSR will energize the rung ONLY for one scan and during that scan the LIGHT_ONS will be energized.

Rung 0 Second Scan: Whether the button is pressed or not, the LIGHT_OSR will not pass the signal and hence the LIGHT_ONS will NOT be energized.

First Scan: LIGHT_ONS is on and the light itself is not on so the rung will be energized and the output light will ON.

Rung 1 Second Scan: LIGHT_ONS is off, LIGHT is on so the light will stay energized.

Second Time we push the button.

First Scan: When the push button is pressed the LIGHT_OSR will energize the rung ONLY for one scan and during that scan the LIGHT_ONS will be energized.

Second Scan: Whether the button is pressed or not, the LIGHT_OSR will not pass the signal and hence the LIGHT_ONS will NOT be energized.

Second time we press the button rung 0 will react exactly the same way as the first time we pressed the button. The difference will be in the rung 1.

First Scan: LIGHT_ONS is on and the light is of so the rung will be de-energized and the output light will go off.

Second Scan: LIGHT_ONS is off LIGHT is off so the light will stay de-energized.

This is the beauty of the One-shot it works like magic.