NO vs NC | 5 PRACTICAL and IMPORTANT Points About Normally Closed and Normally Open Contacts

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We all know how normally closed and normally open sensors and contacts work and how they differ from each other.
But in real-world conditions when we are choosing the instrument switches or other types of discrete equipment for a process, we have to select which one should work with a Normally Open contact and which one should work with a Normally Closed contact.
So, in this video, we'll answer these questions and investigate the real-world application examples of Normally Open and Normally Closed Contacts such as Contactors and relays, pushbuttons, instrument switches, and so on. We also will have a quick look at the NAMUR sensors at the end of this video.
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SECTIONS of this video:
0:00 important questions about NO and NC contacts
0:59 different types of discrete signals in the industry
1:27 NC and NO contacts application in a contactor (Example)
2:05 NC vs NO sensor (Example)
3:52 why normally closed contacts should be integrated into stop push buttons?
4:37 NAMUR switches instead of normal switches
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#NOvsNC #Upmation #AutomationEngineer

Опубликовано:

4 авг 2024

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Комментарии : 99

@braincrackz 3 года назад

I have met so many engrs that practically dont have experience in the field. They dont understand the function of stop button especially when creating a logic in the PLC. But your presentation and explanation will answer their confusing mind. Have a wonderful day

@Upmation 3 года назад

Hey! Thanks for the input. Yes, that was the reason we have decided to provide such a video to clear things up about the NO and NC contacts. Please let us know if you have any suggestions.

@rickymeadows5176 2 года назад

You are absolutely correct, I am an Engineering Process Tech for a team of Engineers which basically translates to a Mechatronics Technician with a two-year Associates degree. And it never ceases to amaze me how "little, if any" some of these 4-year degree guys these days, know about PLC or basic electronics for that matter.

@athilaldurry5880 3 года назад

Excellent videos, Many thanks ,upcoming more videos

@kddk937 2 года назад

A next level of Teaching... Good Luck. All the best..💓

@oserebright6505 Год назад

The type of contactor to be used for the design of this particular High Level switch would be Normally Closed contactor. This is will serve two purposes as the Low Level contactor switch. 1. If there is a damage in the cable, the HMI would identify it as a sign to stop inflow of coolant oil 2. When the oil is filled, circuit opens hence sending same signal to the HMI indicating the tank is filled. But what I really gathered from the selection of the contactor is that it is not just the switching but how to effectively use these contacts to control damages like damaged cables.

@luisvarela8638 3 года назад

Muy buena explicación. Saludos

@yahiaosman8855 3 года назад

Thank you for this video, and I'm waiting more 💯👏

@Upmation 3 года назад

You're very welcome! Please stay tuned for new videos.

@SOGUIREL 3 года назад

Thanks for your efforts. Bravo Monsieur !

@Upmation 3 года назад

Thanks for watching our video! Merci beaucoup, Monsieur! :)

@shankarsuryawanshi7390 9 месяцев назад

Thank you for your efforts and pain in making this video, marvelous!

@Upmation 9 месяцев назад

Glad you enjoyed it and thanks a lot for watching! Please let us know if you have any questions or suggestions and share this video with your friends and colleagues.

@MarEngAlamin Год назад

very appreciative

@user-jh2gw1mg7j 2 года назад

Just priceless content, thanks so much

@Upmation 2 года назад

You're very welcome and thank you for watching! Cheers!

@sureshkumar-ux2nq Год назад

Good examples

@athilaldurry5880 3 года назад

Excellent videos, Many thanks

@Upmation 3 года назад

Glad you like them!

@ringowu6452 3 года назад

Thank you for the sharing.

@Upmation 3 года назад

You're very welcome!

@surendermittapelli3377 3 года назад

good explanation, waiting for the upcomming videos

@Upmation 3 года назад

Happy to hear that! Yes, we do publish new videos by mid-November. By then, please share these videos with your friends on other social media to help us grow as fast as possible! Thank you!

@thesilentgamer4210 2 года назад

hello. i really appreciate your presentation. it is simple , direct and easy to understand. I would like to request also a video presentation on how ESD monitoring should be wired and its relation to the system. Thanks a lotttttt.

@Upmation 2 года назад

Great to hear that! Thank you for watching! I will definitely let the team know of your suggestion.

@MrRumpunch70 7 месяцев назад

Thanks man

@kresnabayuarraziarifin3956 3 года назад

Thank you, very usefull

@Upmation 3 года назад

Glad it was helpful! You're very welcome!

@razerimperator231 3 года назад

Super!I learned the principle of operation OF 3rk1301-0GBOO-OAA2 Siemens DS1-x Motor Starter:)

@Upmation 3 года назад

Great to hear that! Then we have to provide videos on more advanced topics!

@justwatchv 3 года назад

Thank you. Keep it up

@Upmation 3 года назад

You're welcome! Please stay tuned for future videos.

@tamilamuthanthangavel5568 Год назад

Thank u sir

@mohammadbavapoizhithara7132 3 года назад

hi its really help to learn more about plc and plz do more about plc

@Upmation 3 года назад

Great to hear that! Yes, we'll restart publishing videos on 17th March. Please stay tuned.

@marcinlehmann6890 3 года назад

waiting for more!

@Upmation 3 года назад

Hey Marcin! Of course, we'll get back soon.

@nguyentuan-ev1zx Год назад

Thank you very much

@Upmation Год назад

You're very welcome!

@mdnezamuddin6219 Год назад

Tnx

@prasenjitghosh8412 2 года назад

Most help ful video,plese suggest best book regarding INSTRUMENTATION

@Upmation 2 года назад

Thank you! Happy you liked it!

@badshahengineeringvlogs9718 7 месяцев назад

so nice explination can you please start the plc programing session on youtube please?

@realjohnjones 2 года назад

Are there normally Closed transistors?

@sardormuxammadiev250 Год назад

Hello Mr. HL sensor is NC, in normal level HL sensor contact is open but when level gets high then HL switch contact closed .Am I right? My second question is if HL switch contact is damage or sensor damage then what will be happen? Thank you for your answers

@raufmorad4928 3 года назад

Thanks for your video,please put your undertitle in another size or color so that we can see more details as shown.

@Upmation 3 года назад

You're welcome! You should change the subtitle formats of RU-vid in your browser like this tutorial: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-coj5jVx3v4s.html or using this tutorial in RU-vid App: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-xETlLaJDpGo.html The format of the subtitles (size, font, color, background, etc.) is not in our hands and you should change them in your own browser or app to your taste.

@sandyintisel 2 года назад

amazing

@Upmation 2 года назад

Thank you!

@amoslois4600 3 года назад

Dear friend, in 2:20 you assume the LL of the tank ,as a NC switch but is NO switch in fact. (you use the same symbol later as NO).....NOW in 3:10 you assume a NO switch and this time you are right.

@Upmation 3 года назад

Hey! Thank you for the comment. Let me clarify a little bit more here… An NO contact is a contact that should be OPEN UNLESS it gets excited by an external cause (here is the oil). It means that the normal condition for these level switches is when they are not exposed to the oil inside the tank (whether it is the High- or Low-level switch or it has an NO or NC contact). Please consider that the name is “Normally Open” but it doesn’t mean that it cannot gets closed! So, @2:20 when we assume the LL switch is an NC contact but you see an OPEN contact in the picture, it means that it must be excited by the oil (the oil has reached and passed the NC Low-Level Switch), and it has gotten open. (@2:28 you see it is again closed because the oil is below that.) @3:10 we are assuming another situation with a Normally OPEN switch this time and compare it with a Normally CLOSED switch. We say there “let’s assume the LL is normally open one…” and after that, the oil passes the LL switch and makes it closed. Please watch the video completely and from the beginning more carefully and let us know if you have any further questions.

@johnyiu7605 6 месяцев назад

Maybe the main point is that if it is operating normally, it should be closed. So that when there is abnormal operation conditions which would like to be detected in the first place, or malfunction of the sensors/connections, they can be detected at the same time. If it is operating normally and it is open, then there would be problems because malfunctions of sensors or connections can also cause open and it would be perceived as system operating normally. But under this situation if abnormal operation conditions happen, it cannot be detected and the control system will be deceived.

@abhijitraje7462 2 года назад

I like automation video

@nareshp4330 3 года назад

can you explain inductothermal furnace in animation video please

@ericabriguera9211 3 года назад

Hi, is this also applicable to automatic water pump and can also be operated manually? High level sensor and stop push button are NC while low level sensor and start push button are NO?

@Upmation 3 года назад

Hi Erica! Sorry for my belated response. Yes, this is applicable for automatic pumping system. Of course this is an example and in different processes we may want to turn on and off the pump(s) with other instruments such as pressure sensors and under certain circumstances (With or without PLCs). Yes, Stop Pushbutton is NC. Low Level switch and Start pushbutton are NO. The High Level switch in automatic process should be NC (as you've said as well) and in manual process (in which we fill the tank manually) you may not need any High Level Switch. Let me know if you have further questions.

@kayitamoses8580 Год назад

@@Upmation I think for the manual processes you may include some more sensors , for example Extra high and Extra low. This are helpful in a way that if device is run in manual the process can still continue or stop depending on the circumstances

@progressfriday1449 3 года назад

the purpose of the HL sensor, is to ensure that once the oil coolant get to its maximum point the pump should stop. therefore the sensor will be NC switch, once the the maximum point is achieved, the plc send control to open the sensor.

@Upmation 3 года назад

Absolutely correct! Thank you for the answer! One more reason that we use NC contact for the HL sensor (And it is actually the main reason) is to detect its probable malfunction (cable damage or sensor breakdown) despite the process is running or not. If we have an automatic oil charging system to the tank and the cable is damaged, then the oil will probably overflow and no one gets notified if the sensor is Normally Open. *Generally, remember that the LL and HL sensors both should be enabled and send 1 to the PLC when the level of the liquid is somewhere in between them.*

@sophiawang-bourque8912 Год назад

I love your videos can you add a video on drawing PIDS

@Upmation Год назад

Sure we will!

@patelkaran8796 25 дней назад

Is it possible if we use RF signals to operate HL and LL switch with PLC. If we can do this then there will be no problem of cable damage or problems in wiring. It’s just one question, I’m new in this field. Pls don’t take me wrong

@GlowingDiscoveries 2 года назад

Hello, what will happen if there is a broken circuit in the LL sensor? Considering it is NO, nobody can notify the operator.

@Upmation 2 года назад

Hi there! There could be two scenarios here. First, is an *"automatic"* oil-filling system. Second, is *manually filling the tank* . - Assuming the LL sensor is NO, let's see what happens in the first case (Automatic system): If the LL sensor is broken (sending a zero signal to PLC), then the filling pump should work to fill the tank. As the LL sensor does not change the condition to 1 at some point to turn off the pump, the oil level reaches to the HL sensor. Finally, the HL sensor should turn the pump off. You might say, what if the HL sensor is also broken? Bear in mind that, there could be multiple configurations here depending on our expectations and desire. For example, we can add a middle-level sensor to offer more reliability and at the same time, keep the level of the oil exactly between the LL and HL. or we may solely want to add a timer in our PLC program to turn off the pump after getting a 1 signal from the LL sensor. - In the second case (manual filling): The LL sensor is supposed to send 24 volts to PLC at the normal level. If it does not do so, then something is wrong; whether it is a broken LL sensor or a low level of oil in the tank. Hence, someone should check out the condition locally.

@nikitawbu6192 2 года назад

Perfecto

@Upmation 2 года назад

Thanks for your comment and support.

@oleg6517 5 месяцев назад

I suppose the easy principle could be - if you design and alarming device - it should be in NC position during normal operation. And this should be all the time the same.

@jaceknows247 2 года назад

HL is NC because we want it to OPEN upon HL oil 🛢 and shut off power to the auto filling device to prevent overflow...?

@Upmation 2 года назад

Exactly as you said!

@syedaslam2856 3 года назад

Please send the link for namur switch video

@Upmation 3 года назад

Hi! We try to publish a video about Namur Switches as well. Please stay with us. Thank you!

@paulanderson2450 3 года назад

would it be a NO so when the level got to high a signal would be sent back to the PLC?

@Upmation 3 года назад

Hi Paul! Actually, when the process of filling the tank is automatic, the high-level switch should be an NC switch (Sensor). Therefore, as long as the level is below high, it sends a signal to the PLC. And when the oil gets to the high level, its signal to the PLC gets deactivated. The reason is to become aware of any cable damage (or sensor damage) as well as monitoring the fluid (oil) level. The PLC should turn off the automatic filling system when the level reaches high. So we should have an NO low-level switch and an NC high-level switch. Let me know if my answer was helpful or not.

@ajaybisht3301 3 года назад

@@Upmation Hey, I have a query here. As you said in the video, when main coil energized NO become NC. Lets take an example of LSHH having relay output NO and NC and 24V supply is connected to Level Switch. If I connect NO to the PLC then at normal condition PLC get 1 as input and when High level is achieved PLC get 0 as input moreover when wire breaks in that case PLC get 0. Conclusion: Whenever PLC receives 0 it will stop the motor. (that is Automatic) Another case, When I need to hardwire LSHH with motor directly then I need to connect NO as interlock. These statements are made based on my understanding after listening your video. Please let me know if I misunderstood something. Thanks.. 😊

@Upmation 3 года назад

@Ajay Bisht Hi there, Ajay! First, let me thank you for watching the video and asking your questions. First of all, I should correct this sentence which you wrote up there 👉 "when main coil energized NO become NC". 👉 Actually, the NO is NO and the NC is NC! When a switch (it does not matter which type; level, pressure, or any kind of instrument switch) has a built-in NO contact and we excite it (energize it by any means) it gets closed, but it is still an NO contact. Second of all, let me simulate what you said again and elaborate more. Let's assume a switch has both a NO and a NC contact and we use it for the HH level of a tank. For High-level, generally we better use a NC contact. It means the switch is constantly sending the 24 volts signal to the controller (PLC) unless the level of the liquid or material reaches to this switch. At this time, the NC contact gets OPEN so that the 24volts from the switch gets disconnected from the PLC and the logic of the PLC should be written so that the pump turns off immediately. The reason that we use a NC contact for a High level switch is that it is the safest way to monitor the signal from this switch all the time (for any kind of malfunction or cable damage). In these cases, we lose the 24volts as well and the same scenario happens (pupm turns off). We'll then check to see whether the material within the tank reached to the high level OR the cable has damaged (for example)? If the material has reached the high level then everything is OK and the process will be continued without interruption and we see that in the HMI and monitoring systems. If the cable has damaged or the switch has some kind of malfunction, we will repair it and will restart the process.

@Upmation 3 года назад

You may ask how can we distinguish the reason of the pump stop to see if we have to go to the instrument switch location and repair the cable?! Well, if the high level reaches and the pump stops working, then it will restart again after the level of the liquid settles down after a few moments... So there is no problem with the cable or the instrument. As we had explaind in this video, we can use a Namur switch. Normally we use a Level trasmitter AND a high level and low leve switch for having more control over the process. There are other techniques as well...

@vikashranjan6936 3 года назад

@@Upmation great content 💐💐👍🏻👍🏻👍🏻

@ArifinSabuz 3 года назад

Upper Level Switch - NC

@Upmation 3 года назад

Well done! Thank you for collaboration on the subject! If you could explain why do you think so it was also helpful for the others.

@00ffccadobongsili 2 года назад

NC for HL when sensor or switch sense it was full of oil automatically 1 line will be missing and plc will detect it. Normal Oil level should be NC. NO for LL same as your explanation.

@Upmation 2 года назад

Thank you for your precise comment and input! That is correct!

@00ffccadobongsili 2 года назад

@@Upmation keep on sharing knowledge brother. Thanks! New sub here from hvac/r field =)

@Toannguyen-wd5zx 2 года назад

Some segments in the video are stamped not adjacent to each other

@Upmation 2 года назад

Hey, Toan! Sorry I missed your comment. Could you please give me an example? Thank you!

@vaseknovak1272 3 года назад

Switch for high level will be normaly closed.

@Upmation 3 года назад

Hey! Thank you for your answer! It would be great if you leave a short explanation here for others. Thank you!

@thecrazylooser7 3 года назад

Thinking the same because a similar reason. If fails, the liquid will just overflow the tank, causing safety hazards around the place.

@jsmith7310 3 месяца назад

This all comes under the heading " Fail Safe"

@Emin3m1986 3 года назад

2:24 - that’s shown a NO switch 3:15 - and here it’s a NC switch shown...

@rkhrrrmdc3843 3 года назад

You just get confused because of the illustration, bro. But kindly focus on the situation where and when the LL Switch is triggering. I tried to play it back several times before I understand :-).

@Upmation 3 года назад

Hey! Sorry, we have missed your comment due to an unknown reason! Please listen more carefully and @2:20 you hear that we say; "Let's assume that the Low-Level switch is a Normally *_CLOSED_* Switch..." and @3:08 we say; "Now let's consider that the Low-Level switch is a Normally *_OPEN_* switch..." We're trying to consider the possible scenarios and give you an idea about each one so that you can understand which scenario is the correct one and what is the reason!

@Emin3m1986 3 года назад

@@rkhrrrmdc3843 - Mate, you are right. I had to play it few times after you left me the message.

@Emin3m1986 3 года назад

@@Upmation - Yeah, sorry you are right. I though that the iilustration was opposite to what you was saying, but I was wrong. I appologise and thanks for taking your time to deal with me. I hope if are any other "rubber heads" like me, will see my comment and yours and MDX reply. Thank you very much for doing this kind of videos! This are very informative!

@bitebonumbere1426 3 года назад

Please when are you going to populate your RU-vid channel with hundreds of videos?

@Upmation 3 года назад

Hey Bitebo! Thanks for your interest in our videos. We'll restart publishing new videos by mid November.

@bitebonumbere1426 3 года назад

@@Upmation Please how frequently are you going to publish? Daily? Weekly? Monthly? Yearly? Also, how can I financially support the sustenance of your channel? Do you have a patreon account?

@Upmation 3 года назад

@@bitebonumbere1426 We'll publish two videos per month. Unfortunately, we do not have a Patreon account yet.