One shot falling OSF

How it works

Passes power for one scan when the rung goes from true to false, then blocks it while the rung stays false.

How the edge is caught

OSF keeps the rung's state from the last scan. It passes power only when the rung is off now and was on last scan.

ONS uses the same Last scan, but passes on the scan where the rung turns on.

How it's used

Use OSF to act once when something stops or is released.

Motor turned off. Stops went up by 1.

Operands

None. It works on the rung itself.

Common mistakes

• Waiting for a pulse when the input turns onA falling edge occurs when the incoming rung changes from true to false.

Learn it in a lesson

• Edge detection with a one-shotBeginner · 20 min

Related

• One shot rising
• Off-delay timer
• The scan cycle
• Alternating pumps