PLC-5 question

[johnanna]

Hello,
I have homework problem about Anti-plugging logic for motor control with PLC-5 and I draw or wrote ladder program in below, is it work?

Anti-plugging logic:
When the stop pushbutton is pressed, power is removed from the motor starter coils and an Anti-plugging light turns on for 20 seconds. As long as the anti-plugging light remains on, it shall be possible to restart the motor in the same direction, but not in the reverse direction.

Rung 00
...Stop.....FWD_PB1.....REV_Coil.......FWD_Coil
----| |------| |----------|/|------------( )-------
............|FWD_AUX|...................... |...LT1...|
........... |---| |---|...................... |---( )---|

Rung 01
...Stop.....REV_PB2.......FWD_Coil......REV_Coil
----| |------| |----------|/|------------( )-------
............|REV_AUX|...................... |...LT2...|
........... |---| |---|...................... |---( )---|

Rung 02
....Stop.....REV_AUX................Anti-Plugging Light
----| |------| |---------------------[ TON ]-------
............................................... |..T4:0....|--(EN)
............................................... |.PRE 20..|--(DN)
............................................... |---------|

Rung 03
...T4:0/DN...FWD_AUX..................FWD_Coil
----| |------|/|-----------------------( )----------


is it same motor control circuits like that in picture or ladder circuit... http://www.allaboutcircuits.com/vol_4/chpt_6/4.html?

thanks

[leitmotif]

Johanna

I assume you are a student. So am I. Here is what I see.
1. YOu have multiple coils for the reverse and foward. Should only be one coil (output) for one function.
2. Looks like the light controlled by the time delay is OK.
3. EVEN WITH the light I see no anti plugging protection. After pressing stop I can reverse the motor any time I want.

It is after work, I am tiered, so I may have missed something.

Dan Bentler

[johnanna]

Johanna

I assume you are a student. So am I. Here is what I see.
1. YOu have multiple coils for the reverse and foward. Should only be one coil (output) for one function.
2. Looks like the light controlled by the time delay is OK.
3. EVEN WITH the light I see no anti plugging protection. After pressing stop I can reverse the motor any time I want.

It is after work, I am tiered, so I may have missed something.

Dan Bentler

how? show me ladder diagram...

thanks

[harryting]

Johnanna, the best way to see if your logic work is to try it out on a PLC or emulator. If your school or teacher do not have the equipment or allow that, then it's time to take your hard earned education $ elsewhere.

Here are some hints:

Like Dan said, you have two OTE for the same address, that's a no no.
What's LT1 and LT2? They got a purpose?
Where is the Anti-Plugging light turned on? I don't see it
Hint: The T4:0.TT bit is on WHILE the timer is timing. You might use that for... a light, maybe?
Hint: To turn on a timer when something is NOT running, use XIO.
Understand the circuit diagram first.. heck, it's already in ladder form.
Read the book. (RTFM)
PM Ter... Nevermind..

[rsdoran]

PM Ter... Nevermind..
LOL that was just too funny.

[Eric Nelson]

Understand the circuit diagram first.. heck, it's already in ladder form.

That's right... If you enter the last diagram verbatim (except you have to move the OL contact), you're DONE!

Another hint: The timers in that diagram are OFF-delay.

:beerchug:

-Eric

P.S. And yes, the "PM Ter... Nevermind..." was quite funny, Harry... :D

[leitmotif]

Johnanna

As one student to another NO I am not doing your homework for you. I have my own.

On the PLUS side you are close.
You are able to do the ladder logic
- you have shown that
- and showing these guys your effort to date IS IMPORTANT
- they will help you figure it out.
Harryting gave some hints - think about them.

Write you logic in plain language ie
IF motor stopped I can start in fowerd or reverse.
IF motor runs I can start in opposite direction (foward or reverse)
AFTER 20 sec time delay swtich opens (or closes).
Moter will reverse direction.
THEN start drawing switch setups to satisfy the language statements.

Dan Bentler

[johnanna]

Ok, I guess I think it works..thanks