I am fairly new to the plc world and I am stuck on writing the proper logic for a particular alarm condition. I am using a photoeye to detect a part after it has been rejected. I need to alarm if the photoeye does not see a part pass after rejected. I was considering using a timer which would start after the part is rejected, and if the photoeye does not go from off to on before the timer completes to set an alarm. Any help would be appreciated. Thanks for your time.