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  • in the last two videos, we used these Triple five timers to build on a stable circuit with the pulsing output and Amano stable circuit that's normally off.

  • But when we push the button, it turns on and it's deep bounced so that you know, we get a single clean output when we push the button eso this we can use for a clock and then we can also use for a manual pulse.

  • Now what we need to do is figure out a way to switch between the two.

  • And so you might think, Well, we should use ah switch, and I've got a pretty good switch here.

  • This is, Ah, a little push button switch and it's either out or in, and it's got these three leads.

  • And so there's a center.

  • There's a center common pin, and then it's connected to either, uh, this pin or this pin, depending on whether it's in or out.

  • And there's there's two sets, double throws called, and then it's double pole as well.

  • There's sort of two sets that are independent that is correct.

  • The same button.

  • It's a double pole double throne.

  • It's a fairly common type of switch This is another switch here.

  • That's the same thing.

  • And you've got the two sets of three connections there.

  • Of course, this doesn't plug into my bread board.

  • And annoyingly, neither does this.

  • This is actually just a little bit to these pins, basing it a little bit too close together to fit into the bread board.

  • And so what I've done is going ahead and sod erred, Uh, these little header pins to the switch on.

  • So that fits in very nicely into into the bread board.

  • It's the one thing we could do is we could just connect the output of you know, this here.

  • That's not the output.

  • Let's connect the output of that to one side of the switch and we could connect the output of, ah, of our manual trigger over here to the other side of the switch.

  • And then, you know, we could look at the middle of the switch, connect that Thio, you know, led And then, of course, our current limiting resistor here, and we see that it's pulsing.

  • And then we could flip the switch here and now it's connected to our manual clock pulse.

  • We could flip it back and it's connected to the no sort of automatic clock.

  • Paul's there, so this is great.

  • We could we could use this.

  • This will work.

  • Uh, one problem with it is, you know, again we have the switch in here that's not be bounced.

  • And so we could have some situation where, you know, maybe we have a really slow clock pulse, and we're going step by step by step, and we wantto we're watching our computer executing were troubleshooting some problem and we're watching it go step by step, and then we see we see the problem that we're trying to catch developing.

  • We push the button to try to get it back into manual clock pulse to stop the computer and so we can figure out what's going on.

  • Well, if when we push that we have that d balancing problem and we get a couple extra pulse is in there.

  • When we were going so slow to catch that one point that we're trying to we're trying to catch that could be really frustrating.

  • So we really should find a way to de bounce this switch, and you could build exactly this circuit and that would work fine.

  • Um, I'm gonna show you a different way to use the Triple five.

  • Just just for fun, just to see yet another use for the triple five.

  • And so for this next circuit, what we're gonna do is we're basically gonna take advantage of the fact that the Triple Five timer has an S r latch built into it.

  • Um, and we're really only going to use the S r latch.

  • We're just kind of kind of try to ignore the rest of the stuff as much as we can.

  • And what we're going to dio is we're gonna, you know, basically hooked this switch up to imagine we could somehow get rid of all this stuff and just hope the switch up to the S.

  • And they are so in one's in one state, it's it's setting.

  • And then the other state, it's resetting.

  • And then we have our output.

  • The S R latch well, well, actually act as a D bouncer and one of the reasons it will do that is kind of a property of the switches.

  • Which is if we look at this switch, if I just hook up a couple led so we can kind of examine what the how the switch normally works.

  • What you'll see is that you know, it switches between the two states only pushed the switch, which is which is what you'd expect.

  • But if we push it very gently, you see it actually, and then you can kind of get in between.

  • And it turns off that's actually a pretty useful property.

  • So it's called Break before make and you can buy switches that air make before break.

  • If that's what you want biting.

  • Most witches are typically break before make.

  • And so what that means is that, you know, it could be you know, if this is, say, our recent are set condition, let's say we're putting a set into this s are like to forget the fact that it's part of five.

  • Just just imagine we're looking at an S r latch.

  • If we're setting it and then we start to push this switch as we let go, there's not as we let go as we actually push the switch gently.

  • We're kind of in this middle region.

  • Our latch is still gonna be set right.

  • And then as we continue to push the switch down we get into the reset.

  • Um, Then that reset comes on.

  • Well, if there's any bouncing in the switch, it doesn't matter.

  • Because as soon as that first reset happens, the latch is reset.

  • Andare output is gonna be off, and then the same thing as we push this.

  • And then as we gently let go, the reset goes off.

  • We're still reset, right?

  • Because we haven't said it yet.

  • And then even if there's some bouncing as we go into the set, state doesn't matter.

  • Because as soon as its first sees that said, state boom, the output comes on So we can use an S R latch as a d down, sir, with a switch like this.

  • So the question is for using a 55 Well, we could use a Justin S r latch on its own, which we know I've got a video that shows how to build one.

  • But, you know, we can We can use the 555 timer.

  • We can use it's s R latch by essentially using the trigger.

  • Right.

  • So remember, we've got five volts up here, all right?

  • And then we got this voltage divider network, so this gives US 3.33 volts here and 1.6667 volts here and the course zero bolts down here.

  • And so if his trigger goes below 1.6 volts than that sets the lech and then if the threshold goes above 3.3 volts, that resets it.

  • But we're actually gonna ignore the threshold we're gonna We're gonna just tie this to ground, and so this will never this will never do anything.

  • Instead, we're going to use pin four, which we haven't used yet on the Triple five, and that's this reset pin, and it is not wired exactly like this in here, but you kind of imagine it.

  • But this this just gives you kind of a shortcut to the reset.

  • And so if we pull pin four low because it's inverted, that resets it.

  • And if we pull the trigger low below 1.6 bolts that will turn this comparator on and said it until that gives us a way to kind of get into this, this s our latch.

  • And so what we can do is we can hook our switch up, uh, sort of draw the switch down here and so we can hook our switch to ground the middle connection of our switch to ground.

  • And we hook one side up over two are reset and hope the other side over to our trigger.

  • And then if we flipped our switch over to this side, that'll ground the trigger.

  • Which takes this now below 1.6 votes.

  • We should probably have Ah, a little pull up resistor here of some sort.

  • Maybe a one k resistor will d'oh!

  • So that normally, you know, this is gonna be five volts.

  • So to be well above our 1.6 volts and said this will be off so we won't be setting it.

  • But then when we flipped our switch here and this goes to ground, that'll pull this down to zero volts.

  • And zero volts, of course, is below 1.6 volts.

  • And so that'll sit.

  • The flip flop in the output will turn on on.

  • And then when we flipped our switch over to the other side, you know, we do that break before make which you know, this this diagram actually shows pretty well when we break.

  • You know, no big deal.

  • We're not setting it anymore.

  • But it's a latch, so the output stays set.

  • But then when we first make contact over here, even if it bounces doesn't matter.

  • The first time we make contact.

  • Over here, we reset the latch, and then they all put turns off.

  • And so we have this nice d bouncing that we can use.

  • So let's let's hook that up.

  • Okay, here it is.

  • So we got our switch here, and the centre pan is connected to ground, Which, uh which is what we wanted here and the the other two pins.

  • One is connected.

  • Uh, over here, you can see to pin too, and the other ones connected to pin for so just like we've got here.

  • So once connected over here to pin to That's our trigger.

  • And the other one's connected over here to pin four.

  • And on both of those, I have pullup resistors so you can see on pin to end pin for I've got a resistor going to five volts.

  • Draw that over here.

  • But, you know, we want to make sure that these air normally getting five volts unless our switches set pin three, of course, is our output So I just have that going to this.

  • Led for now with the current limiting, you know, 220 home resistor over there.

  • And then, you know, pin sixes are threshold.

  • So we have that just ground.

  • So this comparator is never gonna be is never gonna be on.

  • So we don't have this resetting this way.

  • The only way we're resetting the only way we're resetting the latches through our through our reset pin eso threshold is to ground.

  • And then pin seven is our discharge pin.

  • No need to connect that.

  • We're not discharging anything.

  • There's no capacitor in here.

  • Were just so would you leave that disconnected and then ah, pin five.

  • As usual, we have our 50.1 micro Feyerick pastor in there for, you know, for noise as recommended.

  • So now what we've got is you push the button, a light comes on, push the button again, Light turns off.

  • So not very exciting, but it is fully de bounced and we're using the S r latch part of the 555 timer.

  • And so with that, we've actually got the sort of three different modes that you can use The triple five timer, and we've got the A stable mode where it's not stable.

  • In either state, we've got the mono stable mode where it's got one stable state, which is off.

  • And then when we push this, it goes to another state but then reverts back to the state that it's stable in.

  • And then this is the bi stable mode where it has to stable states.

  • And so it's either in this state or that state.

  • It's now all we need is a bit of logic to combine all three of these into our final clock output, and we'll do that in the next video.

in the last two videos, we used these Triple five timers to build on a stable circuit with the pulsing output and Amano stable circuit that's normally off.

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ビスタブル555 - 8ビットコンピュータクロック - パート3 (Bistable 555 - 8-bit computer clock - part 3)

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    林宜悉 に公開 2021 年 01 月 14 日
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