Search

Premium Membership ♕

Limited Time Offer: Save 15% on PRO Plan with discount code: LRN15 and study specialized LV/MV/HV technical articles and studies.

Home / Download Center / Electrical Engineering Books and Technical Guides / Industrial automation and control guides / PLC ladder and sequential programming for industrial automation

Ladder Programming

Conditional Logic

The PLC scans its inputs and, depending on the program, switches on or off various combinations of outputs. The logic state of the output depends on the input conditions and so the term conditional logic is used.

PLC ladder and sequential programming for industrial automation
PLC ladder and sequential programming for industrial automation (photo credit: acquirecontrol.co.uk)

A simple example of conditional logic could be stated as follows:

A machine switches on if either of two start switches are closed and all of three stop switches are closed. The conditions could be realised by a hard wire solution as shown in Figure 1.

Hard-Wire Conditional Logic Example
Figure 1 – Hard-Wire Conditional Logic Example

The two start switches are connected in parallel. Current will flow if one or the other or both are closed. The start switches are normally open. This means that the contacts are apart and no current flows when the switches are in their normal (or unoperated or rest) state.

The three stop switches are connected in series. Current can only flow if the first and the second and the third are closed. The stop switches are normally closed. This means that the contacts are connected and current can flow when the switches are in their normal state.

Relay
Figure 2 – Relay

The relay is a switch with multiple contacts that is operated when its coil is energised. The contacts are usually capable of carrying a larger current than push- button or limit switches. Large relays for motor starting are called contactors.

The schematic diagram for a typical relay is shown in Figure 2 above.

Title:PLC Programming for Industrial Automation – Kevin Collins
Format:PDF
Size:2.6 MB
Pages:116
Download:Right here | Video Courses | Membership | Download Updates
PLC Programming for Industrial Automation – Kevin Collins
PLC Programming for Industrial Automation – Kevin Collins

Premium Membership

Get access to premium HV/MV/LV technical articles, advanced electrical engineering guides, papers, and much more! It will help you to shape up your technical skills in your everyday life as an electrical engineer.
50% Discount 💥 - Save 50% on all 90+ video courses with Enterprise Membership plan.

More Information

5 Comments


  1. Imin Rotobics Automation Technology Engineer
    Oct 07, 2022

    Interested to travel around the world, training workshops. Can also work directly with the field engineers


  2. James Thwin
    Nov 28, 2021

    it is very good for self study and leaning.


  3. Samirkumar Pardeshi
    Oct 23, 2021

    Very Good Direction for Theoretical and Practical Knowledge.


  4. Rahman Abdo
    Aug 16, 2017

    hi
    i am AUTOMATION & ROBOTICS ENGINEER from Algeria
    now i am scientific researcher in the Modern Control and Artificial intilligence:
    ADAPTIVE Control
    PREDICTIVE Control
    ANN
    Fuzzy Logic Control
    i need new position
    and i want to buy some equipments in Automation ( PLCs; Arduino; …Fluke Scopemeter )
    also:
    i need job anywhere .


  5. AHMED GALAL
    Nov 20, 2016

    PLEASE, I AM INTERESTING DIGITAL PROTECTION RELAYS

Leave a Reply to James Thwin

Tell us what you're thinking. We care about your opinion! Please keep in mind that comments are moderated and rel="nofollow" is in use. So, please do not use a spammy keyword or a domain as your name, or it will be deleted. Let's have a professional and meaningful conversation instead. Thanks for dropping by!

seventy four  −  sixty nine  =  

Learn How to Design Power Systems

Learn to design LV/MV/HV power systems through professional video courses. Lifetime access. Enjoy learning!

Subscribe to Weekly Newsletter

Subscribe to our Weekly Digest newsletter and receive free updates on new technical articles, video courses and guides (PDF).
EEP Academy Courses - A hand crafted cutting-edge electrical engineering knowledge