How does the positive transition sensing contact work

In summary, the positive transition sensing contact has a value of 1 for the scan in which it detects a change from off to on and a value of 0 for all other scans, as shown in the time diagram.
  • #1
ongxom
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Homework Statement


Draw the time diagram for this PLC ladder

eae91958d05b133ec3b888b5464bf3d1.png

Homework Equations





The Attempt at a Solution


I am trying to understand how does the positive transition sensing contact work.

Definition : The positive transition sensing contact has the value 1 if it receives value change from off to on in one scan.

According to the time diagram I can see that :
Scan 2 : PB1 raises from 0-> 1 (off to on) so PB1 = 1 for this scan only
Scan 3 : PB1 remains 1, no changes so PB1 = 0 for this scan only
Scan 4 : PB1 drops 1 to 0 so PB1 = 0 for this scan only
Scan 7 : PB1 raises from 0-> 1 so PB1 = 1 for this scan only
Scan 8 : PB1 no change (still on), PB1 = 0 for this scan only
Scan 9 : PB1 (on-> off), PB1 = 0 for this scan only
Scan 12 : PB1 (off-> on) PB1 =1 for this scan only
Scan 13 : PB1 remains on so PB1 =0 for this scan only
Scan 14 : PB1 (on-> off) so PB1 =0 for this scan only

Am I understand it correct ? I know how to draw the diagram, just confused in determining the correct values PB1.
 
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  • #2

Yes, your understanding is correct. The positive transition sensing contact will have a value of 1 for the scan in which it detects a change from off to on, and a value of 0 for all other scans. Your time diagram accurately reflects this behavior. Keep in mind that the values for PB1 are only for that specific scan and will change in subsequent scans depending on the input.
 

1. How does the positive transition sensing contact work?

The positive transition sensing contact is a type of electrical switch that detects changes in voltage or current. It works by using a spring-loaded arm to make contact with a conductive surface, completing the circuit and allowing current to flow through the system. When there is a change in the voltage or current, the arm moves and breaks the contact, signaling the change to the system.

2. What is the purpose of a positive transition sensing contact?

The purpose of a positive transition sensing contact is to detect changes in voltage or current and send a signal to a larger system. This can be used in a variety of applications, such as in electronic devices to indicate when a button has been pressed or in industrial settings to monitor the flow of electricity.

3. How is a positive transition sensing contact different from a regular switch?

A positive transition sensing contact differs from a regular switch in that it is designed to detect changes in voltage or current, rather than simply turning a circuit on or off. It is also typically more sensitive and can detect smaller changes in the electrical system.

4. Are there any limitations to using a positive transition sensing contact?

Like any technology, there are limitations to using a positive transition sensing contact. It may not be suitable for extremely high voltage or current applications, and it may not be as precise as other types of sensors. Additionally, it may be affected by external factors such as temperature or moisture.

5. How can I test if a positive transition sensing contact is working properly?

To test a positive transition sensing contact, you can use a multimeter to measure the voltage or current in the circuit before and after the contact. When the contact is triggered, there should be a noticeable change in the readings. You can also physically press the contact to see if it is responding properly to pressure. If you have any concerns about the function of the contact, it is best to consult a professional for further testing.

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