Need Help with truth tables

Hey Guys, sure could use some help with truth table project, this is new to me, any help is appreciated.

the project is this.

I have 5 limit switches all wired normally open, when any 2 of the switches are made the machine will run and operate normally. if at any time more than 2 switches are made an alarm will sound.


I used output 1 for my machine run output, and output 2 is my alarm output.

below is what i have come up with, is this correct?

You haven't got all the possibilities for the alarm condition, for example, SW1, SW2, SW4 all ON, SW3 and SW5 OFF.

The spec also doesn't cover all the possibilities. What about when fewer than 2 switches are ON?

Looks like you attempted to let your outputs "drive" the setup of the truth table. What I usually do is first create table with ALL posssible input combo's and then start filling in outputs, looking for missing states as I go. eg
SW1..SW2..SW3..SW4..SW5..OP1..OP2
0....0....0....0....0....?....?
1....0....0....0....0....?....?
0....1....0....0....0....?....?
1....1....0....0....0....?....?
0....0....1....0....0....?....?
1....0....1....0....0....?....?
0....1....1....0....0....?....?
1....1....1....0....0....?....?
0....0....0....1....0....?....?
1....0....0....1....0....?....?
0....1....0....1....0....?....?
1....1....0....1....0....?....?
0....0....1....1....0....?....?
1....0....1....1....0....?....?
0....1....1....1....0....?....?
1....1....1....1....0....?....?
0....0....0....0....1....?....?
1....0....0....0....1....?....?
0....1....0....0....1....?....?
1....1....0....0....1....?....?
0....0....1....0....1....?....?
1....0....1....0....1....?....?
0....1....1....0....1....?....?
1....1....1....0....1....?....?
0....0....0....1....1....?....?
1....0....0....1....1....?....?
0....1....0....1....1....?....?
1....1....0....1....1....?....?
0....0....1....1....1....?....?
1....0....1....1....1....?....?
0....1....1....1....1....?....?
1....1....1....1....1....?....?

On my example I try to show all combinations Sw1 goes thru both states before I change sw2 and so on and son that way I can be reasonably sure I have covered all combinations and I can look at the pattern and be easily find a particular combination. On yours you may have covered all bases (I don't know) but I have to check every line as opposed to "pre-empting" my pattern and go starting to the section I wanted. BTW I left the ouputs as ? coz I figured you can always fill them in and that way I won't get blasted if I make a dum mistake.

How about one-shots and an integer.

All inputs off, integer = 0.

Every input coming on, increments the integer.

Every input going off, decrements the integer.

Count = 2 = Run.

Count > 2 = Alarm.

Wow, this sure sounds like a problem from an introduction to digital systems class. My guess is next you will need to createa a Karnough map to group the inputs and write a logic equation.

As another post suggested, write out all possible inputs and there possible states. I remember doing this by writing in binary from 0 to (2**x - 1) where x is the number of inputs. this would give you:

Inputs Outputs
00000 y,z
00001
00010
.
.
11110
11111