EOL Resistor Wiring Explained (Short visual tutorial on EOL resistors)

Hey, guys. Hayden here again from Alarm Systems store. And today I thought I would do a quick tutorial on end-of-line resistor wiring for most situations. So we have another video that goes way in-depth on resistors, how they work, why they work, so on and so forth. I'll link that down in the description so you guys can check it out if you want to. However, it's a bit long-winded, so I thought I would just do a very quick tutorial to show you guys how you would wire these specific types of end-of-line wiring. 

So, when deciding how to wire your sensors, you have the option of either directly connecting your wires to the sensor without using a resistor, or you can use end-of-line resistor settings, which are wired one of two ways, depending on whether your sensor is a normally closed or normally open detector. So I have this motion here just so we can use it as a reference. But basically, this is a motion that allows both normally closed and normally open operation. So with your alarm system, the first thing you need to do is decide whether or not you want to use resistors. If you don't, that's perfectly fine. However, they are recommended. If you're going to skip them, though, you need to make sure that your panel can support normally closed and/or normally open detectors. Some systems, like the DSC Neo that I have here, only work with normally closed sensors (without resistors), and if you're using a normally open detector, you do have to use a resistor, which is just a bit of extra work and programming. You just swap over specific sensors that need to be resistored and so on and so forth. However, some systems can basically do normally closed and normally open operation, such as the IQ Pro that I've put out a bunch of videos on. 

So once you've decided that, you're just going to take a look at your sensors and see how you're going to have to wire them. So with this being our example here, basically if we were just going to, you know, say it, use a normally closed operation for a sensor, we would take our zone wires here. Now this is a motion. So it would also have power wires. But we're not talking about those today. So I don't have them hooked up. But this is connected to zone one here. If we were going to use normally closed operation, we would just take our wires and directly connect them to the C terminal, which is the common, and the NC terminal, which is the normally closed side of the switch. So it would look like this. Now, if your system can support normally closed sensors, that's all you have to do. You just set it for normally closed, and it'll work. If you want to use normally open, and your panel supports it. You'll do the exact same thing, except you'll take one of your zone wires and you'll connect it to the NO side of the switch. So it would look like this. 

Now, if you do want to use resistors, depending on whether your device is normally closed or normally open, it's going to change how you attach the resistor. So, with normally closed detectors, you are going to wire the resistor in series. With normally open, you wire it in parallel. So, in the case of a normally closed circuit, what we're going to do is, since yellow here is kind of our positive it's connected to Z1. We're going to connect it to the NC terminal just like this. And since we have to have an in-series resistor, we're going to take the resistor and connect it to the C terminal. And then we were going to splice the return wire to the system to the other end of the resistor. So it would look like this. But essentially, this creates an in-series circuit with the resistor in line with the wiring. So as the electricity flows, it goes in through the normally closed switch inside here, through the resistor, and then back to the system. 

If you were going to be using normally open operation, however, you do still just connect your wires directly to the detector. So you'll use the NO and then the C terminals. However, with the resistor, you're going to wire it in parallel, which means that you are going to take the resistor and stick it in both terminals as well. Sorry, that was me. But, this is what it would look like if it was a normally open circuit. So essentially, with a normally open circuit, there is no electricity that can flow through the detector itself at any given time. So we run the resistor in parallel so the electricity can flow into the detector through the resistor and then back to the panel. So those are your three most common types of, you know, wiring setups. It's either going to be, you know, normally closed, normally open, in series resistor, or in parallel resistor, as we have here.

Now, for a brief explanation of why you do it that way, I'm going to use this door contact as essentially a switch. So to explain what I mean by that, basically, even though this is technically just a switch itself, we can use it as basically, you know, an internal switch for a device like that motion. So if we have our, you know, two metal contacts as part of our switch here inside the motion, in a closed state, these are touching each other. So what happens is when you connect one wire to one side of the detector. Is connected here. So electricity is flowing through from the system into one side of the switch. When it's closed. That allows the electricity to flow through to the other side of the switch. And then the other wire takes that electricity back to the panel and completes a full circuit with a normally open setup.

This is what it would look like. Basically, the electricity flows in from one side. It's one side of the switch. This is disconnected. So that's where the electricity stops. So if we want to use the resistor with our normally open circuit, essentially all we're doing is we're bridging that gap in the switch with the resistor. That's what wiring a resistor in parallel does. So essentially, instead of having that gap there, you're just going to have the resistor bridge that like so. So the electricity is flowing through one side and hits the side of the switch. The system sees the resistance, and then it flows back out. Now whenever the contact triggers, all it does is it closes this circuit. And what happens is electricity is always going to take the path of least resistance. So as the electricity flows, it now directly goes through the switch instead of the resistor. So once it gets back to the system, the system no longer sees the resistance. It basically eliminates all the resistance on the circuit. And that's how the system knows that that sensor has been triggered. 

Now with a normally closed circuit. Like I said, you're going to have it sitting like this, where it is always closed and the electricity's allowed to flow this way. So to make the system see the resistance, we have to attach the resistor in series like so. Now, with a normally closed circuit, instead of having a gap here, the electricity is always just going to be able to flow through the switch. That's why we have to change the resistor to an in-series resistor. That way the electricity flows in one side, goes through the switch, hits the resistance, and then goes back to the panel. Now, whenever that sensor is triggered, all it does is it opens this up. So now basically no electricity can pass through the circuit at all. That's how the system knows that this sensor has been triggered. 

So I'm not going to go super in-depth. Like I said, this is just meant to be a quick tutorial video. However, those are the absolute basics of resistor usage on an alarm system. So if you're trying to decide whether or not you want to use resistors, or you just needed a wiring tutorial for them, hopefully that covers it for you. Now, 99% of people are only ever going to use single end-of-line resistors like I did here. However, if you are interested in double end-of-line resistors, that is covered in our other video that's down in the description. So if you want to, feel free to go check that out. Or if you just want to know more about, you know, how the system actually senses that resistance, like what it looks for in each particular case, that video covers in depth. Pretty much everything you could ever want to know about using resistors on an alarm system, so hopefully that was informative. If you guys found it useful, please leave a like and subscribe down below. And if you have any questions, by all means leave a comment, and we will answer as quickly as we can. Otherwise, though, I will catch you guys on the next one.