IC Not Working? Or Incorrectly Wired?

[snester]

Hi there,

I am working on a project with an AND IC logic gate. I have 74LS08 IC (https://www.electro-tech-online.com/custompdfs/2011/11/8.pdf) which doesn't seem to be working. Here is a picture of the circuit:

**broken link removed**

Here you can just see one 'switch' wire to simulate a TRUE into 1. and FALSE into 2., however, the output is still on. I have connected two actual switches up but still the output is on.

Question 1: The output seems to be High all the time regardless of input. Should the IC be giving High output when no switch wires are even attached?

Question 2: Could it be that the IC is simply not working or that I've wired the circuit incorrectly?

Many thanks for any assistance!

Steve

 

[House0Fwax]

You should ground all unused inputs.
Also, stranded wire on breadboards are a bad idea, you'll get terrible connection issues.

 

[Grossel]

Question 1: The output seems to be High all the time regardless of input. Should the IC be giving High output when no switch wires are even attached?

This is normally. Any unconnected input is treated as High. But any inputs not used should be grounded anyway.

 

[crutschow]

I don't see the FALSE connection. An unconnected input, with TTL ICs, goes to TRUE, not FALSE, as noted by Grossel.

 

[Nigel Goodwin]

There's an obvious lacl of any capacitors on that breadboard!.

 

[Grossel]

. . . An unconnected input, with TTL ICs, goes to TRUE, not FALSE, as noted by Grossel.

I said "High", not "false".

 

[crutschow]

I said "High", not "false".

You misunderstood my comment, which I see was ambiguous. I was agreeing with you. I meant that, as you stated, an unconnected goes to HIGH or TRUE. It does not go to LOW or FALSE as the OP apparently assumed, since he tied one input to HIGH and left the other input open.