Master Minecraft Redstone – Lesson 6: Basic Logic Gates!

Hello everyone and welcome back to redstone 101 i’m your host val death and today we’re going to continue with our intermediate lessons with lesson six basic logic gates logic gates they are the foundation of advanced circuits and now that we’ve spent time looking at the basics of how input and output works circuits

Moving signals around and how the basic uh circuit blocks of minecraft can be very useful for us the next logical thing will happen is you’re going to want to start doing things based on the outcome of multiple signals and that’s where gates come into play we with um making logical decisions

Based on the various inputs of different input signals yeah oh what is this is it’s raining or something of course it’s gonna rain it’s never rain when i’ve done any recordings here until now well we’ll just go with it okay so we’ve already seen the most simple

Uh kinds of gates and it is the not gate also known as the inverter we’ve seen this a few times a is not equal to b whatever the input a is b is not that it is the opposite so here we can already see we have the input the switch here on the

Lamp showing its state is off this is our inverter circuit very simple signal going into the block the torch not being powered is now powering the output however of course if we turn this on we know that powering a block a torch is attached to inverts the torch turns it off which

Turns off our output there we there we have it a simple not gate whatever a is b is not that the output is off when this is on and this is off that is on it’s most simple gate we use them in conjunction as simple repeaters before the introduction of the actual

Repeater block as i said this is known as the inverter the next most practical gate that you’ll probably be using is the first one that takes two inputs is known as the and gate when both inputs a and b are on and they both are on c is also on

So here’s output node c and see it’s a pretty simple thing three blocks some torches here coming together into an output torch connected on this block so when i turn one of them on the output is still off because this torch is still held on by this other

Redstone torch it’s only until i turn both of them on that both of these top torches are off releasing power on this allowing this torch to come on and turning on our output only when both a and b are on is c on when one of them goes off the output will go

Off it doesn’t matter which one that one or this one okay now there’s also an opposite of an and gate if we were to take the same gate and put an inverter on the end of it we would have a not and gate also known as a nand

Gate only when the inputs a and b are on is the output c off otherwise the output is on excuse me so as we saw before this is exactly the same thing as the and gate we just removed the torch at the end providing the inverting or not capability thus when both of

These are off the output is on and only when i turn them both on does the output go off as soon as any one of these are off the output is back and boom there it goes okay so that can actually be pretty useful uh depending on what you want to have

Happen of course it turns out that the not version is more useful in computers computing and large arrays of logic but most people will use the and version for simple circuits around their homes in minecraft next up is the or gate this also takes two or more inputs and it’s a pretty simple

Logic when either input a or input b is on the output c is on so here we got two input nodes in our output node simply signals flowing into the same block or going out so when either one is on the output light will be

On as well that one’s on this one’s on they’re both on it’ll be on it doesn’t matter but as long as one of them is on that’ll be on now or gates are susceptible to having signals flowing backwards since they’re generally so simple like this you could have a signal coming onto the

Output which would come backwards through the flow and hit an input and generally when we’re thinking about circuits and signals there’s a steady flow of input to output so to prevent this we put a repeater here ensuring that the flow power only goes this direction towards the repeater’s output

A repeater will block a signal coming from the output will not allow it to reverse backwards when we use it in this way it is called a diode and we’ve seen we’ve seen this before but here’s where it starts becoming important especially as we’re using multiple signals around

We want to make sure that one input signal does not contaminate another input signal so really this is actually not perfectly safe if you wanted to be really safe about it you would protect both input signals get some repeaters here like the following you could actually do that to protect

All of them ah you wouldn’t need that to be honest you could just have the output now that both inputs are isolated is what it’s called from the output if we did send a signal on here it would be they would be blocked by each of these diodes we wouldn’t need a

Further one going out but in practice uh generally just to keep things for sure you know how things are flowing around a lot of people will do that but i don’t generally think it’s necessary unless you have power flowing around in other places of course around or above they could you know

Interfere with the signal going into these blocks but we’ll go ahead and leave it here just because that’s how we started but this is definitely safer that’s what this is talking about now just like the and gate the or gate also has a direct opposite the not or gate known as the nor

Gate when either input a or b is on the output is off only when inputs a and b are off is the output on so right here you can see that we have both a and b a and b off so the output is on

If either one of them turns on this will go off there we go or if this one goes on it also goes off if they’re both on it’s still off it doesn’t matter either or but when they’re both off it finally allows it to come on

Now likewise we have a output diode here a repeater limiting power flow but just like before it is actually safer to isolate both inputs like so now of the basic logic gates the and the or you’ll use those for some combination of simple simple things but the most

Useful actually early on is the xor gate pretty scary oftentimes because it’s a little bit of a bigger circuit but its behavior is actually much more useful the output c is also a double input a and a b the output c is on only when one of the inputs is on

A or b but not when both of them on it’s an exclusive or gate is what it’s called so it’s only when one of them are on so we have our two a and b inputs here is the basic xor circuit using just blocks and torches it’s a little bit more complicated and

Here’s the output c currently it’s off now when only one of them is on our output will go on as well so turning this on our output is on if i turn on the second one the output goes off that’s not good we don’t you know that’s well that’s good it’s what

We want that’s how the circuit operates now if i were to turn off this one our output is back on only when one of them is on only b is on so it’s on turn that off as we expect it’s off and this one comes on it’s on

But if both of them are on the output is off no matter what combination of flipping the levers that is an x or gate an exclusive orchid only one of them can be on now while this is a great for the basic demonstration oftentimes you may not have this much

Space to do a circuit you may need to pack it in with a lot of other things maybe limited for space so we can use some of our compact redstone blocks that minecraft has provided specifically the comparator block to make a very compact xor gate this is the most compact possible

Now what you must understand is that first of all you have to have the comparator set with the torches on normally when you place a comparator the torches are off like that in this mode we need to have them on for the mode that we’re trying to use

Here to put them in this behavior of an xor gate but here you go you can see dust dust behind it both of them are facing forward a block behind our output block right here output c so just like before when only one of them is on will the output be on

So that was on if i turn this one on it goes off bonus one’s off and only this input is on also is it on so it works great just like we want any combination of flipping the levers you can see these comparators remembering state between them but

The way they operate you don’t have to worry about the details they’re doing the right thing for us to make the gate work as expected the competitors must be right clicked after the placing such that the torch is lit when no power is going into them just like we see here

Just like this now here is a another example of that same xor circuit using comparators but with having the two input levers right next to each other maybe you want the two input blocks right next to each other versus having to be two blocks apart like this this one is a

Little bit more expensive it’s a little longer it uses two repeaters in addition but the behavior goes off is the same now it’s on only one of them is on the output and just like the rest of the common circuits um oh actually i’m sorry uh the most common

Use of the xor circuit xor gate is to control a single device from multiple points say a light system so think about it this way let’s say you had one light switch or this is a uh an array of lights say connect this to a bunch of lights

In your house and they’re all on or they’re all off and you want to have multiple switches throughout the house to turn them on or off so let’s say i come in this is the switch nearest my indoor come on turn them on things are on run

Around let’s say when i go out the back door and turn everything off like i want to flip the switch and turn all the lights off or come in and flip the switch turn all the lights on let’s turn all the lights off i can independently control the light switch from either lever

No matter what the other levers flip to you know often times if this is set on then i can’t the output won’t respond to this other switch but using an xor gate it will okay let’s see now just like all the other basic gates the xor gate

Has an opposite a not xor gate known as the x nor gate and here is the kind of spelled out logic of it when both inputs a and input b are in the same state when they’re both on or both off the output c is on otherwise when the inputs differ in state

The output is off so as you can see right here both inputs a and b are the same they’re both off so our output is off looking at the circuit it’s basically the exact same as the xor gate with another torch on the end so it’s a not

Xor gate but the behavior is different you know the opposite so as soon as i turn any one of them on the output light goes off let’s go to reset time here and they’re both on it’s also on but as soon as one of them is off it’s

Off and they’re both off it’s on or when they’re both on it’s on there we go that’s the xnor gate that can be kind of useful i guess but most people will use the xor gate for light switches just because it’s a little simpler now just like i said all the circuits these

Opposites are basically the same circuit with a knot in front of it just having another inverter stuck on the end there now with all this moving of signals around diode use is if ever as important if not more so because we want to keep the current the direction flowing from input to output

Always we don’t want gates to have input signals polluting their output lines now we’ve seen repeaters and comparators used as diodes before but we can also use a torch repeater and the unique blocks slabs glowstone and stairs so first up is the torch repeater the redstone torch repeater

Before the repeater block was in play this was the only way to actually extend redstone signals beyond their 15 block limit but it also acts as a viable diode mechanism as with the the redstone torch attached to a block this attached to a block here here we have a torch repeater setup an

Input a and then output b and normally this would be like a an actual output here when i turn this on it would be on and this would be you know between very far away right we would use this to extend the length but we want to show that if we actually

Sent a signal inwards coming in the wrong direction that the torch blocks it and we don’t see our input line getting lit up that’s really really good it’s not polluting our input signal it’s a diode there we go we talked about that now the same uh well not the same thing

Glowstone slabs and stairs can also be used to create diodes because of one of their unique properties in which they do not allow power on their top surface to transmit below to a block directly underneath now they allow power from their top to be transferred in another way

Which we take advantage of but this restriction allows them to be used to make diodes so let’s take a look at that here’s a simple glowstone diode i have an input here that is on and the output is off the power on top of the glowstone is

Not allowed to transfer down to the bottom even though there’s plenty of power here i can do 15 blocks length so this is only three it should totally it just totally stops it as a diode and here’s some other examples this is a regular block where we don’t have that effect

Where signals can go freely but here we show a slab a glowstone block and a stair each blocking the signal from going forward there are diodes so if this was our input signals on this side and we were trying to send signals this way they would not pollute and

Cause bad things to happen now this like i mentioned before this property of these blocks or one of their other properties is basically what allows them to transmit power vertically between each other since it’s not transmitting power from this one to the ground it’s doing it to the block

Next to it below we can create a pattern like this where power is snaked up and transmitted vertically we looked at this uh much earlier on in the episode or in the series so he goes off on off on we’re moving signal up there so i hope this has been an informative

Lesson for you guys these basic circuits be should be helpful in tying together various uh devices in your homes you’ve been making sorting systems and switches and lights and doors all kinds of good stuff after this we’re going to be doing some more advanced lessons a little bit later on memory circuits

Clock circuits and maybe even some more advanced stuff after that i think the only thing we’ll do is probably bud circuits we’ve already covered i think pretty much by far all the basics and for a good part you guys should be able to figure out what’s going on and other people’s work

And debugging and troubleshooting your own works please leave me any questions comments concerns queries conundrums you name it in the section below give a like if you enjoy this video and series and subscribe if you want to see more thanks a lot and i’ll see you guys next time