Need help !!!!!!!!!1

As in "Help. Someone do my homework for me?"

If you don't at least make an effort you won't get much sympathy here. Make an effort and you'll get lots of help.

OG

chbryan34 said:

Design a PLC ladder logic program to control the operation of an alarm system consisting​

of three (3) Horns (HORN_1, HORN_2, and HORN_3) and four (4) normally open input
sensors for malfunction (INPUT_1, INPUT_2, INPUT_3, and INPUT_4) using the
following sequence:
- HORN_1 must be energized if any two of the inputs are activated.
- HORN_2 and only HORN_2 must be energized if any three of the inputs are
activated.
- HORN_3 and only HORN_3 must be energized if all four inputs are activated.
- Notice that no two Horns can be activated at the same time.
- Do not use latch and unlatch instructions.​

- Assign sequential addresses to the input and output devices starting from bit 1.

Click to expand...

Hello bryan;
Not doing your homework for you, for sure. But here are some (I hope!) useful tips:
Start by attributing addresses to your inputs and your output contacts for the horns; retain internal coils for each activation condition: "2 inputs active", "3 inputs active", "4 inputs active"...
Begin your program by writing one network to test the "4 inputs active" condition, and activate the specified coil.This should cause no problem, simply AND the 4 input signals...

Next do the same for the "3 inputs active" coil. Except that you must make sure that only three inpust are active at the same time (or else the "4 input active" condition will activate the "3 inputs active" coil at the same time, and they must be mutually exclusive).
So you must write logic that could look like this:
(Input1 AND Input2 AND Input3 ANDNOT Input4)
OR
(Input1 AND Input2 ANDNOT Input3 AND Input4)
OR
(Input1 ANDNOT Input2 AND Input3 AND Input4)
OR
(NOTInput1 AND Input2 AND Input3 AND Input4)
Then "3 inputs active" coil is active

Write similar logic for the "2 inputs active" coil, ant note there are more combinations to be checked...

Now that you have 3 mutually exclusive coils (they will not be active at the same time), create 3 rungs activating the required horn on each specific condition, as required.

Hope this helps,
Daniel Chartier

Note; You can skip the intermediate coils if you want to, but in real programs it is more elegant and easier to debug if you do use them...

Wouldn't it be faster to just do a quick count of the number of inputs that are on and then do numeric compares?

bernie_carlton said:

Wouldn't it be faster to just do a quick count of the number of inputs that are on and then do numeric compares?

Click to expand...

You are right, Bernie;
And there are 2 or 3 other (and simpler) ways to do the same logic I can think about.
But I presumed the OP was limited to the given instructions, so I was trying to stay within the homework specs. Well maybe the temp coils were out of bounds too, but as I said they can be used or not, as one cares.
Regards,
Daniel Chartier

The only bounds I saw were DON'T use latch or unlatch.