Door Opener Model

This model demonstrates the control concepts behind a “hands-free” door system.

The user breaks a light beam - sensor combination to start the open process.

The system has the following control devices.

Input side of door

• Switch
• Red Led
• Light sensor
• Light source on sensor

Output side of door

• Switch
• Light
• Limit switches for door
• Motor

The system is an ideal introduction to a number of design problems where the door system may be used in a food processing system or a sports event.

The powerful Intellecta software makes it easy to set up a number of control processes that use the worksheet concepts.

The worksheet idea breaks the problems into small control strategies that can be individually designed and tested.

This is presented in Task 10. Other tasks are as follows:

Meat Hall controller

Here the workers may approach the door with a large carcass on their backs. It is unsafe to stop and press a manual door switch. The best idea is to use a passive type of switch where there is no need for contact.

So, a possible solution is based on the breaking of a beam of light across the path of the worker. The output of the sensor is measured and a valid condition is generated when the light level drops below a certain value

The worksheets have internal structure that define their operation.

The strategy may be as follows:

• Wait for light beam to be broken
• Flash the light to indicate the door will open
• Turn on the motor and run the motor until the limit switch is pressed that indicates the door is open
• Close the door and start flashing the outside light to indicate a  worker is inside the cold room.
• Wait for a certain time to give the worker time to open the door from the inside by pressing the switch
• Sound an alarm if the door is not opened.
• Open the door in a final emergency option.

Wait for light

The ON icon turns ON the green light on the door entrance.

The value of the light sensor is compared to a value of 2.5V. An On is generated when this falls below 2.5V and this passes to the SheetStop icon. This stops the operation of this worksheet and starts the next one.

Flash Light

This is a simple strategy. The total duration for the flashes is set up in the worksheet property

Open Door Strategy

This strategy has to run three parallel processes. The generator flashes the inside and outside lights. This safety feature means that users inside and outside the cold room know that the door will move.

The set-point motor combination start the motor in a forward direction. The door will open.

The limit switch-Sheet stop combination stop the operation of the sheet and progress to the next sheet.

Flash Light

This strategy flashes the inside and outside light for a period defined in the property box of this worksheet.

Question.

How do you flash the light for a number of times that is set in the worksheet rather than in the property box of the worksheet?

Answer:

Use the counter to count pulses in software ( the pulses come from the generator icon).

The number of pulses is compared to a set number in the Comparator icon. The ON value fires off the SheetStop.

Note: The counter icon can also generate a trigger pulse at a specific count and this can fire off the SheetStop.

This removes the need for the Comparator function.