# Help with sum logic gates n..........

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#### umer007

##### New Member
Can sumone plz gimme an electrical analogy for NAND gate, NOR gate and a XOR (EOR) gate plz. By electrical analogy i mean a ciruit diagram that describes how the gate works.

I am tryint to attach an example of a AND gate i made on Paint but it said bmp not allowed or sumthin. Plz tell me how to post so i can show u a example or if u know wt im talkin abt plz answer post.

TYVM

#### Russlk

##### New Member
jpg format is acceptable, you need a scanner or bmp converter.

This is my anolagy for the gates:

#### Attachments

• LOGIC_144.jpg
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#### umer007

##### New Member
plz. tell me wt A. B and C stand for

#### Styx

##### Active Member
A and B are the input to the descrete logic

C is the output

Also altough you asked fo r NAND,NOR,XOR the simplest gate AND and OR can be made from two diodes and a resistor - although can only have a fanout of 1

#### umer007

##### New Member
I wz wonderin if u cud gimme a analogy in the form of a circuit that is attached.

#### Attachments

• thing.JPG
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#### ljcox

##### Well-Known Member
umer007 said:
I wz wonderin if u cud gimme a analogy in the form of a circuit that is attached.

The circuit you attached is an AND gate using switches. If you label the switches A and B, then the lamp glows when A AND B are closed.

If you put the switches in parallel, you have an OR gate. The lamp glows when A OR B (or both) is closed.

To create an analogue of a NAND gate using switch contacts, connect 2 normally closed switches in parallal. Thus the lamp does NOT glow when both switches are operated.

To draw circuits for this forum, I draw them in PowerPoint and then save them as a .gif file. This file can be attached to a post.

Len

#### umer007

##### New Member
Yes i know but i need NAND, NOR, EXOR in that kind of drawing. Plz post if u know.

#### ljcox

##### Well-Known Member
umer007 said:
Yes i know but i need NAND, NOR, EXOR in that kind of drawing. Plz post if u know.

I think you posted this while I was editing my previous post to describe a NAND analogue.

A NOR analogue would be 2 NC contacts in series. So the lamp does NOT glow if A OR B is operated.

I'll draw a XOR and post is shortly.

Len

#### umer007

##### New Member
wud u mind drawin NAND, NOR and EXOR for me plz. It wud help me understand them alot.

TY

#### ljcox

##### Well-Known Member
Here are a NAND, NOR and XOR gate. I'll leave you to draw the lamp and battery.

NAND - lamp does NOT glow if A AND B are operated

NOR - lamp does NOT glow if A OR B are operated

In the XOR case, the lamp glows when A is operated or when B is operated but NOT if both are operated.

This is how lights in houses can be controlled by 2 switches.

Len

#### Attachments

• Gates_172.gif
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