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# Can you have a logic circuit with 3 outputs?

I have an assignment to do and the question is regarding building a logic circuit for an industrial oven.

There will be three input points labelled A B and C to a control circuit. It states that logic 1 must indicate the temperature is correct.

Three LEDs will be used to indicate the conditions of the circuit, with only one LED on at a time.

Red - if the temperature is correct at 1 point or at no points

Yellow - if the temperature is correct at 2 points but incorrect at any one point

Green - if the temperature is correct at all three points.

Is this all one circuit, and three outputs or have I misunderstood the requirements for this question? If it's one circuit how do I make it so only one LED is on at any one time?

If anyone could help that would be massively appreciated - I've been sat down for hours and I just can't understand what to do.

### 3 Answers

- JohnLv 61 month ago
I would use an Western Electric, telephone stepper switch. Cost prohibitive and heat sensitive. LOL. A simple logic circuit, Boolean Algebra.

- MorningfoxLv 71 month ago
Three inputs, each goes to three circuits.

Circuit #1 controls the red LED.

Circuit #2 controls the yellow LED.

Circuit #3 controls the green LED.

Now you just have to design each circuit. That's 3 different designs.

Using a 3-8 decoder is a good idea, but I bet you're supposed to use just basic gates: AND, OR, NOT, NAND, NOR.

- billrussell42Lv 71 month ago
as I understand it, there are 3 outputs each driving a LED.

you have inputs A,B,C

red if A,B,C are all 0 or if one of A,B,C = 1

Yellow if any 2 of A,B,C =1, the other =0

green if A,B,C all = 1

I'd use a 3-8 decoder which gives you outputs of 0 thru 7

A B C output

0 0 0 A

0 0 1 A

0 1 0 A

0 1 1 B

1 0 0 A

1 0 1 B

1 1 0 B

1 0 1 B

1 1 1 C

so you take outputs 0,1,2,4 to a 4 input OR gate for red

outputs 3,5,6 to a 3 input OR gate for yellow

output 7 for red.

An ALS138 for the decoder, and a bunch of gates following it for the OR gates, and some LED drivers.