Wiring Boolean Gates: Invert & AND Gates

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Discussion Overview

The discussion revolves around the challenge of wiring a 'NOT' gate using basic components, without relying on pre-wired chips like the 7400 series. Participants explore various methods and components that could be used to achieve this, including switches, relays, and transistors.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in wiring a 'NOT' gate and seeks advice on how to construct it without using pre-wired chips.
  • Another participant describes the 'NOT' gate as a fundamental gate, suggesting its representation as a triangle with a circle.
  • A suggestion is made to use a 7400 NAND gate as a 'NOT' gate by tying its inputs together, although this involves using a pre-wired chip.
  • Some participants propose that constructing a 'NOT' gate from scratch using only wires and switches is challenging, with one humorously suggesting relabeling a switch to achieve the desired output.
  • A link is provided to a resource that describes using normally open and normally closed switches to create a 'NOT' function, which aligns with earlier suggestions about relabeling switches.
  • One participant asserts that it is impossible to create a 'NOT' function using only AND gates, while mentioning that NAND gates can be used to create any function except possibly XOR and XNOR.
  • Another participant questions how to construct a 'NOT' gate using transistors and diodes, emphasizing the exclusion of mechanical devices like relays.
  • There is a discussion about using solid-state devices, with one participant suggesting a configuration involving a resistor and a transistor to create a 'NOT' gate.
  • Another participant elaborates on the transistor method, explaining how the input voltage affects the output voltage in a 'NOT' gate configuration.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of constructing a 'NOT' gate from basic components. While some suggest methods involving transistors, others emphasize the difficulty of achieving this without pre-wired chips or mechanical devices. The discussion remains unresolved regarding the best approach to create a 'NOT' gate from scratch.

Contextual Notes

Participants mention various assumptions about the components available, such as the exclusion of relays and the use of solid-state devices. There is also a lack of consensus on the most effective method to wire a 'NOT' gate without using pre-wired chips.

eax
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Is it possible to wire a 'invert gate'. 'AND' gate is easy to wire

Code:
VCC
|
|
----------------out
   |   |
   |   |
   |   |
   A   B
----------------GND

If a or b or both are grounded (is 0/low) then output is 0. No matter how hard I try I still can't build a circut that will function as a 'NOT' gate. Anyone know how to wire a 'NOT' gate?

Thanks in advance!
 
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the "not" gate is one of the main gates. Isn't it a single gate on it's own, looking like a sideways triangle with a little circle at the end?
 
I don't know what you are trying to do, but a 7400 NAND gate can easily be used as a NOT gate by simply tying the two inputs together and using them as a single input.

I'm not sure how you would wire an AND gate to behave as a NOT gate if that's what you are trying to do.
 
Iam trying to wire the circut of a 'NOT' gate using wires not other "pre wired" chips such as 74...
 
eax said:
Iam trying to wire the circut of a 'NOT' gate using wires not other "pre wired" chips such as 74...
I can see wiring up an AND gate or an OR gate using just wires and switches. But I don't see how you could wire up an effective NOT gate without at least using a relay.

Unless you simply take a switch and just re-label it's ON and OFF labels so that it does the opposite of what it says it's doing. :smile:

Seriously though. How else are you going to do it?
 
Here you go,... http://library.thinkquest.org/12666/switches.html"

This site just uses N.O. (normally open) and N.C. (normally closed) push-button switches.

They simply call the N.C. switch a NOT gate. When there's no signal (i.e. the button is NOT being pressed) then the output is high. If there is a signal (i.e. the button is pressed) the output goes low.

This is basically the same thing that I've suggested about having the switch do the opposite of what it is marked. (i.e. pushing it turns it OFF vs. pushing it turns it ON.)
 
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You cannot wire any combination of AND gates to produce a NOT function. However, you can come up with any function using a single or combination of NAND gates with the possible exception of XOR and XNOR. But I could be wrong on that last part.
 
hes asking how to make a NOT gate from scratch. if you think for a few minutes u can figure out how to create an AND or and OR gate simply with 2 transistors, but how do you construct a NOT gate? I've been trying to figure this out myself. this is assuming u can't use switches - aka the input is from the output of another gate. how would you invert this using transistors, diodes, etc (no mechanical devices such as a relay)?
 
YOu're trying to do this with just wires and switches? No use of relays or solid state devices (transistors, diodes, ect...)
 
  • #10
how do u do it with solid state devices but NO relays?
 
  • #11
Don't know, that's why I'm asking.
 
  • #12
you can do it with a resistor and a transistor as follows

. vcc
. -----
. |
. R
. |
. Vin-----T
. |
. -----
. gnd

hope that's clear.
 
  • #13
Yeah, I believe that NOTs are the simplest gates. They're basically a single transistor, along with any resistors appropriate to preventing it from burning, of course. Basically, all you have to do is connect the input voltage across the base and emitter, and take the output voltage across the collector and emitter. If the input voltage is high, current will flow through the transistor, and there won't be a large voltage drop across the collector and emitter: hence, the output voltage is low. Conversely, a low input voltage will not allow current to flow, and the output will be high. Thus, we have a NOT gate.
 

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