I opened an old PC keyboard and found this IC - 7406N, "hex invertor buffers/drivers with open collector outputs"
Can I do anything useful with this and an Arduino? Seems like I can use it to switch higher current devices.
http://www.ti.com/lit/ds/symlink/sn5406.pdf
You could like... make a keyboard.
You should start with a bulb and a resistor.
It's outputs are 40mA, same as the arduino's IO pins. You can power it with up to 15v and then have those voltages as outputs, but then you lose the ability to control it with the arduino's 5v logic. All it does is implement the NOT function which you can do in software on the arduino any time you need it.
Do something without the Arduino like a ring oscillator.
>>910942
I might do. Mainly because it got a bit hot during desoldering so it needs testing.
>>910953
>but then you lose the ability to control it with the arduino's 5v logic
What do you mean? I can't send 5v to the input and have 15v out?
>>910957
If you power the device with 15v it expects 15v logic input. Arduino uses 5v for 1 and 0v for 0. Both of these will be seen as 0 by the chip.
>>910958
You power the chip from 5V. You can use the (open collector) output to drive stuff up to 30V/40mA.
>>910958
>If you power the device with 15v it expects 15v logic input.
Damn. I thought the point of a transistor is that you can activate it with a smaller voltage/current. Or is it just current?
Are these thing basically transistor arrays?
I made this circuit and the LED goes on. Even before I got to connecting the input. Shouldn't it be off until I do that? The pin you see the resistor at is 1Y (a collector).
Am I doing it wrong or did I roast it?
>>911011
However the LED goes off if disconnect the IC's Vcc.
>>911013
If I ground that pin's corresponding input (base 1A) then it goes off.
I thought it was off by default and needed a voltage applied to open the collector.
>>911011
That's the cutest circuit diagram I've ever seen
>>911022
>I thought it was off by default and needed a voltage applied to open the collector.
On seeing this diagram, I guess scratch all I said. Looks like you ground the input to ground the output. All those transistors and resistors seem like overkill though - can anyone explain?
>>911028
>Looks like you ground the input to ground the output
I think I mean grounding the input to close the output. Is that right? Once the input emitter grounds, it grounds the output base and stops sinking at the output.
>>911029
its a hex inverter buffer
hex means there is 6 on one chip
inverter means the signal is inverted, google 'not gate'
buffer means it boosts voltage or current or something like that
so yeah sounds right.
>>910963
disregard the retards, like this man >>910958.
that's what the datasheets are for.
>>911044
High impedance between input and output.
>>910908
Acquire more of them and build a computer. Acquire even more of them and make it so massively parallel that it beats your Arduino and then your PC in performance.
>>911044
>its a hex inverter buffer
>hex means there is 6 on one chip
Ah right, I thought it meant something to do with hexadecimal. Don't know why I thought that, in the sober cold light of day that seems ridiculous now.
>>911052
>You've double-inverted it. Look at your own diagram:
Yeah I realised the inversion action. Like when I saw a diargam where an open collector was connected to an input pin (with a pullup), so the pin received voltage until the collector opened, grounding it. So it inverted it.
So I'm effectively inverting the inversion because I'm having the driving current go through the collector, rather than using the collector to ground (and thus take away current)?
Still though, when I read about open collectors I got the impression that the output collector was closed by default until the base got current - in this case, it's open by default until the input (an emitter not a base) is grounded.
Is this just like the same kind of "duality" as NPN vs. PNP transistors or something?
>>911074
>>911263
precisely. You only need to 0.2~2V on the input side but can output 15 V. What am I missing?
What's the point of this chip? Set a pin to low and the out pin begins to sink. Can't I just do this directly with a microcontroller?
The only difference is that the LED or whatever grounds through the chip not the microcontroller but is that an issue?
Even without a microcontroller, can't I just set up the same concept without this chip?
>>911286
>Set a pin to low and the out pin begins to sink
You mean "rise". See >>911052. It's an inverter ("not gate"); its output is the opposite of its input.
>the LED or whatever grounds through the chip not the microcontroller
That's the point of a buffer. You can drive it with a weak current, and it'll drive something that needs a stronger current. It'll also compensate for voltage drop, say from a long link such as a keyboard wire.
>Even without a microcontroller, can't I just set up the same concept without this chip?
Sure, you can make one out of a chain of transistors. Ponder this concept more, and you might gain an insight into the integrated circuit revolution of the 1970s.
>>911286
You can drive shit which requires more (or less) than 5V.
You can drive shit which requires more current than standard TTL (and many other families) can sink.
You can do that from standard TTL levels.
You can do that relatively fast.
You can use it to implement a bus without requiring 3-state buffers and the associated arbitration.
Also, it's an ancient IC from an era when the microcontrollers didn't exist.
>>911291
>You mean "rise". See >>911052. It's an inverter ("not gate"); its output is the opposite of its input.
Rise? I ground the input and the output grounds. There's nothing inverting about that. Unless the ground connection is used to draw current *away* from a component, rather than through it.
>Sure, you can make one out of a chain of transistors. Ponder this concept more, and you might gain an insight into the integrated circuit revolution of the 1970s.
Why would I even need to make a chain of transistors? All it seems to do is relay the action of grounding through an unneccessary middle man.
Here's another one of my "cute" diagrams to illustrate how pointless it seems to me. What am I missing? The top one performs the exact same function as the bottom no?
Pretend there are resistors on the LEDs in both, however.
>>911320
>The top one performs the exact same function as the bottom no?
Okay it doesn't actually, I see. I drew it wrong. But you could replace the first diagram with one that diverts current away from the LED and that would be the same right?
I think this is what I'm trying to illustrate.
Ground either and the LED goes off. No "chain of transistors" needed.
>>911296
>Also, it's an ancient IC from an era when the microcontrollers didn't exist.
Funny you should say that because the keyboard also has an 8051A-P microcontroller on it too.
>>911044
>buffer means it boosts voltage or current or something like that
Ah, that's another piece of the puzzle. I was thinking buffer in the computing sense. All these sources just bandy about terms like this as if there could be no possible confusion. Which is confusing.
>>911330
Although true that it may boost voltage or current sourcing/sinking in this case, it isn't always true.
A buffer is merely a device that isolates the input from the output.
This is a hex inverter buffer.
First off, the hex is 'six', meaning that there are six of these per chip.
Inverter just tell you that a logic High at the input will resultin a logic Low at the output. It also tells you that a logic Low at the input will result in a logic High at the output.
Buffer tells you that no current [very little, uA typically] will flow from or to the input. It essentially isolates the output from the input.
This one just happens to have a wider range of operation than the Arduino's microcontroller and therefore can be used as a means of controlling larger currents or voltages.
>>911328
To put it differently: the reasons for their existence are older and independent of microcontrollers.
>>911341
but still has it's applications with them. Just not as common.
Quite happy you brought it up. hadn't really considered the gradual decrease of the humble inverter.
What are other IC's that aren't commonly around in consumer electronics anymore?
word to BCD decoders come to mind.
>>911346
*BCD to seven segment
>>911346
Standard logic in general is quite unpopular nowadays. Most products have either very few standard logic chips, or none at all. The arithmetic functions, like adders, have been niche stuff for years. And if BCD to 7-seg decoders are uncommon, then decade counters like 7490 are even less common.
>>910938
*actions and shitty humor*
Are you 12?
>>911472
>randomly pulling apart a keyboard thinking he could salvage something
Its obvious he is
>>911473
It was broke, so why not? I'm fairly new to electronics, so yeah, I thought I'd just have a look.
>>911326
The point you've missed twice now is that you can use the inverting output as a current *source*.
Sure, you can tie the LED between VCC and an inverting current source to make a convoluted wire, but only a stupid person would do that.
>>911320
>Why would I even need to make a chain of transistors?
So the magic smoke doesn't come out.
Either that or you know better than Texas Instruments, and should probably let them know they've been doing it wrong this past half century.
>>911549
>Either that or you know better than Texas Instruments, and should probably let them know they've been doing it wrong this past half century.
Maybe I should because last night I built a circuit that grounds the current away from an LED and makes it go off. Not an IC in sight. Nor magic smoke.
See, if you're going to be flippant then so am I.
Besides, half this thread is people telling me it's a useless IC that has no use.
![latest[1].jpg](https://i.imgur.com/3blGBfi.jpg "latest[1].jpg")
>>911688
>useless IC that has no use.
Whoops.
>>911549
>The point you've missed twice now is that you can use the inverting output as a current *source*.
How? I just can't see that.
It's just a gate that opens a path to ground as far as I can tell, no source of anything.
>>911693
Aw c'mon guise. This is making no sense. All I see is a switch controlled by a convoluted Mouse Trap-style arrangement of transistors that I cannot see the merit of.
How can it be a current source when it's just a switch to ground?
>>910961
>You power the chip from 5V. You can use the (open collector) output to drive stuff up to 30V/40mA.
I don't understand. That's a meagre amount of current isn't it? A Darlington pair should drive much more than that - this is a Darlington triplet at least. What gives?
All those transistors and resistors just so current can go into the collector of one and straight out of the emitter of that same one.
>>911747
>> Open collector: another way to connect gate outputs to the same wire
>> gate only has the ability to pull its output low
>> it cannot actively drive the wire high (default ��pulled high through resistor)
https://courses.cs.washington.edu/courses/cse370/99sp/lectures/08-SeqEx/tsld026.htm
It doesn't seem like it can act as a current source.
>>911751
I'm confused, are we talking about buffers or open collectors?
>>911747
>That's a meagre amount of current isn't it?
Normal TTL outputs are limited to 5V/16mA and that 8051 mentioned earlier is even wimpier.
>A Darlington pair should drive much more than that
If you want darlingtons, use darlingtons. They're much slower though.
>current can go into the collector of one and straight out of the emitter of that same one
Huh?
>>911769
The first three are there to make the input look like a TTL gate input is supposed to look. The last one is there to produce that open collector. The remaining one is an inverter so that the combination inverts.
>>911793
>Huh?
Here. For all its complexity, this is the end result right? That transistor opens a path to ground.
Why is everyone having such a hard time understanding why this appears totally superfluous to me?
Also, here's a totally sensible invention by Rube Goldberg.
>>912190
That's fucking stupid.
Why don't power supplies have just a diode and a resistor in them? You know to rectify and then reduce the voltage?
That's all you need right?
Grow a fucking brain moran
You know how much it costs to create a new integrated circuit? A lot of money. But hey I guess these guys were just total retarded right pouring money into this worthless chip that nobody would buy? I mean it must be worthless, there is no possible reason on earth that it needs to be so complicated because you thought about it for 10 seconds without any clue of the design considerations involved.
Oh right except people did fucking buy it because its in your keyboard so it can't be that dumb after all.
>>912190
Yeah, everything in it is superfluous. Just replace the whole IC with a piece of wire.
>>912213
>>912237
FFS I GET THAT THERE *MUST* BE A PURPOSE BUT I CAN'T FUCKING *SEE IT*!!!! I'M ASKING FOR AN EXPLANATION BECAUSE *TO ME* IT *APPEARS* TO HAVE NO PURPOSE. *TO* *ME* IT JUST LOOKS LIKE 4 TRANSISTORS USED TO OPEN 1 TRANSISTOR IN AN UNNECESSARILY CONVOLUTED FASHION. IF THE MEANS TO THE END IS SIMPLY TO OPEN THE TRANSISTOR, THEN WHAT DOES IT FUCKING MATTER WHETHER THERE'S A CURRENT/ABSENCE THEREOF APPLIED DIRECTLY TO THE BASE - *OR* WHETHER IT GOES THROUGH, I DUNNO, FOUR HUNDRED AND SIXTEEN OF THEM BEFORE THE SAME END RESULT IS ACHIEVED. THIS IS HOW IT *SEEMS* WHEN MY *UNTRAINED* EYE LOOKS AT IT AND NONE OF YOU CAN EVEN EXPLAIN IT, YOU JUST GO "HURR DURR WELL TEXOS ONTROMUNTS MUST HAVE BEEN WASTING THEIR MUNNY ALL ALONG LOL YOU FOOL".
FUCKING AUTISMAL PRICKS!
