Your videos are a great help. I’ve been building control systems for about 40 years, and I’m still learning. It would be a big help to some if you did a video on encoders / open collector inputs, etc. I do about 2 systems a year with encoders, and they can be pretty confusing to anyone just starting out. I really appreciate the work that you do on these videos.
you're such a good dude Tim. you refused to put the manufacturer on blast that had misleading sinking and sourcing information. You don't care to hear about credentials. You care about the next generation of automation professionals. I hope to reach your level of skill and professionalism one day, and i can't wait to take your class.
For one of my application (egg counting system) previously I used PNP, and the result was that I was getting short on the counts by 10k. I then used NPN, with 24V going to the PLC com and receiving a negative input on the PLC card, and the cout was aproximately perfect.
Just had my 3rd interview/ walk through at a juice bottling plant for an electrician position. Hoping I made a good impression with the controls engineer and others and land the job. You can only learn so much in vocational training and on the job. I feel like I'm learning everyday in this field. Thank you for helping me review basic skills, that are imperative to plant maintenance work. Very helpful.
Thank you so much! Currently struggling through a PLC class for engineering school...your video helped me a lot with understanding the wiring, concepts, and terminology. Cant wait to check out you other content! thanks again!
@@TimWilborne 1.can we use capacitive touch pad switch (with 5v /24 v dc relay )......in place of start/stop/selector switch ? in a 24 v dc PLC? 2. As we are using retentive timers......how we can design ladder logic for PLC.. so that process start ITSELF after power supply resumes ? (i.e ..not starting with the help of start switch)
You included the AB manual as a ref! Nice!! :) Ok, so to do PLC's.... well, I have to pay attention to PNP and NPN but the simple side of me says, "It's a switch, it does not care, it is going to complete the circuit!" Yet an Output has power going OUT from it to something like a relay! .......and the Inputs have power going into it because it needs to see the 24vdc coming in as confirmation that the input is indeed there.
Now Finally I clearly understand Sinking and Sourcing. Always Love Your Videos. I have Learned a lot from You Videos and looking forward to do the same in Future. Keep up the Good Work Tim👍
Another good video would be reading the diagrams on sensors and how to wire them to your plc. Some are very confusing especially when you have a retro fit or replacement in the field that doesn't match the original.
Love it , i watched so many video about sinking and sourcing they are fantastic but within 1 week i forget everything lol. Now with your simple picture everything gone stay for lonnngggg time in my head. Regards
I’m sure someone has already answered your question to why NPNs are faster than PNP. It has to do with transistor make up. The mobility of electrons is faster than the mobility of holes. Cute video!
I was not understanding the reason why the PowerFlex inverter's wiring diagram shows an inverted logic regarding the polarity of the sink or source Digital Input. But after watching this video I realized that in this case, the reference is the wiring and not the internal connections of the digital inputs. Thank you for the explanation.
To answer the question why do we have NPN & NPN? It was my understanding from an "older instructor" who has been in high speed programming and impressive resume told me that either PNP or NPN (not sure which one, I think it was NPN) predates the other. So the reason why you have both PNP and NPN is because in the past they could only make the electronics one way. Then they figured out how to make the PNP, I believe. That the best I recall from a few years ago. I recall him saying what Tim said in the video, that the concern was that if a wire is pinched or something cause something to ground the could cause somethiing to run which you did not want. In the case of PNP, you was more likely to blow a fuse.
Good explanation Mike. NPN is older and for some reason slightly faster. I'm going to do a video on it as soon as I have time to study on it. Thanks for watching!
The real problem with all this is the confusion between conventional vs electron current flow. Could have fixed this in the 40's when electronics really took off. But the scientists and engineers like to confuse technicians as much as possible. Thanks a lot Benjamin Franklin!
great video I'm use to the PNP/NPN terminology. when it comes to sinking/sourcing I always have to stop and think for a second. I also like power/not power I never heard that one before that's a easy way to think about it. something that might help some people or it may just be me. but when I think of PNP setup meaning both my inputs and outputs are PNP. I think of it as Positive in/Negative common Positive out. Or Positive In to input/ Negative common on input card/ Positive to common on output card. Or NPN Negative to input/Positive to input card common/Negative to output card common. again I don't want to confuse people but that's just how I think of it.
Coming from PCB design world, this seems unnecessarily complicated! I’d expect sensors to have push pull outputs (so will sink and source) and the plc to just have a high impedance input (so neither). Although the plc should have optional internal pull down or pull up resistors to deal with sensors that require it. That’s how it works at the microcontroller level anyway. I’d be interested in the reasons why plcs don’t do that. I guess it means some sensors can have just 2 wires rather than 3. But is that all…?
Sinking or sourcing, or high side switch or a low side switch 😂. Active high or active low, pull up or pull down 😁 Sometimes it makes a hell of a confusion. It's nice that someone took the time to clear things up in understandable way!
It's much easier to find that burnt wire and replace the IO fuse than it is to figure out why intermittently the machine does something on it's own. Especially given that wires+vibration+metal = short to ground.
Im looking for this because i am troubleshooting an auto hallowblocks/concrete paver machine.. its not operating automatically and i found out some inductive proximity sensors are defective.. i also wanna know what type of sensor is needed in this kind of automation, is it npn/pnp, n.c or n.o.
this sounds all confusing but in the end i understood that i understood this long ago. its not anymore difficult to understand then when you transport pizza and salad and put the salad on top of the pizza it will heat up the salad but if its under the pizza it wont. when you put a frozen turkey on top of the produce in your fridge it will freeze the produce but if its below it wont. those concepts of dependency logic and positive/negative states really isnt intrinsic to electrical or logical systems. but what do i know i am no EE lol. for every sensor its just important to think what happens if the wires get wedged in a door or other part of machine and make contact internally and what happens if they get ripped of and cant make contact anymore. according to this outcome you have to choose the safer configuration even if it means buying a different sensor.
As a rule of thumb I was taught it is common practice in 24vdc applications to sink inputs and source outputs. I was wondering your take on that philosophy?
I had to run sensor wires into the 1769. Never worked with this plc. Called tech support and also no idea how it gets wired. So with some guessing I got it to work.
Before this video I thought I had an understanding of inputs outputs and sensor wiring. Now not so sure. Let me explain. I am an electrician. So I would bring 24v to a limit switch sourcing then from normally open on limit to digital input which is my syncing. Then this would fire the output to let say a solenoid on a valve to get it to open to open back up the limit. I would then bring 0v blue white wire back to 0v terminal block. Not that confusing before. On analog circuits I would use Belden cable with red black shielded pair. Inputs black wire positive outputs red wire is positive. So pressure transmitter would be my analog input sinking and sourcing because the transmitter get both power and sends signal back along same wire through 4 20ma. Then the output would fire sending power to pressure control valve. Sourcing. Where I am now confused is on digital input sourcing. I thought digital input received the signal and digital outputs send out 24v. Analog outputs send out milliamps or millivolt usually. When I need better counting circuits I use sensor that use fiber optics and bring them back to an input card that understands fiber. Now I have to go back and relearn where I am lacking in my understanding sourcing syncing pnp npn digital inputs and outputs vs analog inputs and outputs
This is a typically hard concept for people to follow, mostly i think because of the nomenclature not used anywhere but electronics. I once again was out at a customer helping get a process running, and somebody had wired an NPN sensor to their sinking inputs. I always think of it in as they look phoenetically, NPN sensor (P is the common between the two. Positive resides on the common of the plc) PNP sensor (N is common between the Ps, so N [0v] is the common on the plc). Sourcing to me can just mean the source of the voltage comes from this point, so activating a PNP Sourcing sensor means the return wire to the plc input will have voltage and must complete the circuit with the Common being the 0vdc wire or "N".
I'll add too that it's almost comical how many technicians I run into that say "If the lights on, it's working, so it doesn't make sense why the input won't turn on, I think the PLC is bad." A GREAT tool for people to use, veteran and novice, is the Turck TB3-CP80. It will not only power sensors, photo eyes, etc. but also tell you if it's working and whether it's NPN or PNP, normally open or normally closed. If anybody does troubleshooting with sensors, they need it.
Hello Tim, I was wondering if you ever created a training video on the effects of grounding the positive output terminal on your I/O power to the cards. Could you show the effects on Grounding the Positive Output on the DC Power Supply on your Oscilloscope. Then preform the same illustration on the grounding of the Negative Output side of the Power Supply. Then show how this effects sourcing and sinking PLC'S I/O cards as it relates false Input Signal, Output turn on with out the signal from the Output Card. Also could you explain the effects of lifting the Ground on the Secondary side of the Power Supply. Thank you
A simple way to understand this is, If give 0v to DCOM then it's sinking and if you give +24v to DCOM its sourcing. And for sensors, NPN requires sinking and PNP sourcing.
@@TimWilborne Hey Tim, it's nice to see you reply so quickly. Of course, you've way more experience than me regarding plc's. So, I was thinking what other manufacturers swap these terms? I've mainly worked on AB,ABB, Siemens and Schneider modicon and I found they all use the general method of sourcing and sinking. Pardon me if im wrong.
I have searched everywhere and I can find the meaning of the “Q” in the manuals and the “-Q” but with the line on top of it! I thought it would something like NO and NC, but I haven’t found nothing explaining it! Help please! The are always on the cables white and black 2 and 4.
I’m wondering if you could post a troubleshooting video for finding bad inputs for sinked devices. For some reason I recently had my butt kicked on a AB 500 system sinked input card with a shorted wire. Thanks
Ok here goes, Zero experience sparky - I have a 24v motor that controls a sliding door with 2 proximity sensors, when the door is closed(sensor indicates green and amber light) and I press the open switch the door will open until it reaches the outer end sensor and the motor stops. Now the closed sensor turns to green only. When I press the close button the door doesnt close. I have 24 volts at the switch and the switch is working properly. My question is - is the outer proximity switch supposed to supply power to the junction box to signal for a close command?
If I wanted to simply monitor the dry 'alarm' contacts on a bunch of field devices (which are NC, and 'Open' on alarm), should I use sinking or sourcing PLC inputs?
I know you probably explained this, but I have to ask. I’m assuming this is the same with VFDs,. I see drives with sink/source, is this for a secondary circuit to control some load with the drive or are these some inputs that can be programmed to start a drive? I know that’s not a plc question but It’s related. Thanks
The principle is the same, but the terms can be swapped just as I discussed in this video. For AB, it is exactly the same on their drives as their PLCs.
Hi Chris. Most of it was from the College of Hard Knocks, that is why we try to make sure we make this information freely available to others. Thanks for watching!
Yeah, this video on INPUT basically does it. My boss told me today that OUTPUT would be the other way around - - simply check wether your PLC OUTPUT is PNP or NPN, then complete the circuit with your load towards the opposite polarity. Loads would have no polarity
Hi Tim,I'm Gabby from PNG and new to plc and automation so please can you assist me on my assignment, about wiring a simple plc rack test bench for testing plc I/O cards. Thank you.
giving too much information often confuses and also time of vedio increases, to try to keep things simple and short..in layman language source means send and sink means receive...
@@TimWilborne I never thought that even you will read my reply, but you did, that shows how serious you are about your work. Thanks for sharing great knowledge that will even help to me clear any doubt in future..Thanks a lot again.
Companies that have their ducks in a row have electrical standards that specify sinking input modules (sourcing devices). Same with big integrators. Why? Because electricians, technicians & engineers are used to seeing schematics with +24 volts on the left & DC Common on the right like every other schematic in the world. Because most industrial electricians are also used to physically wiring them this way. The only reason people use sourcing input modules is an infantile desire to be 'different'. The career field is already complicated enough without having to remember that common is now on the left &. In short, using sourcing inputs & sinking outputs is a good way to irritate people you'd really rather have on your side
Normally, outputs are supplying power to your device = outputs are the SOURCE of power for your device. Inputs are provided power from your device = inputs SINK up to a device for their power. 😆 couldn't think of a good one for sinking
While that is typical for most Allen Bradley configurations, it isn't true for all brands and almost all can have sourcing inputs and sinking outputs. The most notable being high speed applications.
would it be also called active vs passive channels? where active channels need two terminals to complete a loop vs a passive channel where you only need the return (-) to complete the loop.
No active and passive usually indicate whether a signal is powered by the loop or powered externally and is usually used for analog signals such as 4-20 mA
