Adding timer to motor start push button.

Does anyone know the best way to add a horn to a start button that stays on for 10 sec then shuts off and the motor starts.

Which PLC brand,make, model are you using?

It will be a Allen Bradley, micro logic 1200,more likely. It is for a machine rebuild

Based on your prior posts I'm going to assume its an AB PLC.

Program your motor/start stop logic to an internal bit. Use the internal bit to start a timer and the timer DN bit to start the motor. The timer TT bit is used to turn on the horn during the ten seconds the timer is timing.

XIC STOP_BUTTON BST XIC START_BUTTON NXB XIC RUN_MOTOR BND OTE RUN_MOTOR

XIC RUN_MOTOR TON MOTOR_START_DELAY 1 10 0

XIC MOTOR_START_DELAY/DN OTE MOTOR_STARTER

XIC MOTOR_START_DELAY/TT OTE HORN

That work out good. I have one more question, I forgot to state it before. The system will have a auto and manuel switch. The horn only needs to come on in auto.

2 things:
1) consider sounding the horn for 10 seconds and then having a 2 or 4 second wait before machine start - that gives someone caught up in the machine time to yell out loud, and be heard by someone who can then run and hit an e-stop. Not that they should be in that dangerous a place w/o a tagout/lockout, Its a touch safer.

Also a touch safer: make the horn sound in 'manual' also.
If your button is making things move that cannot be seen by an operator, then it is much safer to have the horn every time it starts. (If its conveyor, I can find an OSHA spec that says this specifically =)
Thing is, the OSHA spec doesnt say *how long* the horn has to sound...

The time I programmed this for our material handling (coal) conveyors, it took 4 rungs similar to what was posted below.

-John

It is for a similar setup. Our system separates scrap metal, ferrous and non ferrous

You said you could find the OSHA specs. I wouldn't mind seeing them.

I am looking at ASME B.20.1-2009, "Safety Standard
for Conveyors
and Related
Equipment"
section 5.11.2

Let me do some more looking...

-John

"(1) When a conveyor that would cause injury once
started is automatically controlled or must be controlled
from a remote location, an audible device or devices
shall be provided that can be clearly heard at all hazardous
points along the conveyor where personnel may be
present. The audible warning shall be actuated by the
controller device starting the conveyor and continue for
a required period of time before the conveyor starts. A
flashing light or similar visual warning may be used in
conjunction with, or in place of, the audible device if a
visual warning is more effective."

It doesn't say how long you need to sound the horn/flash the lights....but this is for conveyors only...machine tools are probably a different game.
-John

jtashaffer,

Your profile says maintenance tech, but I have been reading the various posts that you have done and i have have some questions and comments for you.

1. While we don't mind helping you, is this your first program or machine that you have worked with?

Forgive me for asking this question, but these are simple things to deal with.

The reason for asking is quiet often, many new programmers jump into a project head first into the water and fail to see the shark(s) in the water.

I say this because of my first programming jobs.
While i did what was asked of me, i failed to follow through with all the logic and caused the machine to jam later on in the cycle. Several hours later, i got the machine running, but we lost a lot of money on the project.

Stay focused and follow the program logic from start to finish. It may sound dumb, but often times, you discover that your quick fix, may result in other problems later.

I learned that lesson the hard way and on more than one occasion. Just trying to pass on some wisdom from my mistakes.

regards,
james

The audible warning shall be actuated by the controller device starting the conveyor and continue for a required period of time before the conveyor starts.

Click to expand...

Notice it doesn't say that the audible device has to be on CONTINUOUSLY, but that the "audible warning" must continue for a required period of time. It may seem a small point, but I have found that it is much better to sound the horn in 1.5 to 2 second bursts, separted by 1.5 seconds of quiet time, continuing for the required period of time. Then if someone IS in the equipment, you have a better chance to hear him yell, and everyone else will not get a headache listening to the loud horn. Those short pauses between blasts do wonders for employee morale - a rest before the next on-slaught. Your people who work in the area will love you for this small little change that costs nothing with a PLC program!

Lancie's suggestion is an excellent idea and its super easy to do.

On a timer with a one second time base, bit T4:0.ACC/1 toggles at a two second rate, off for two seconds, then on for two seconds. If you program XIO T4:0.ACC/1 as a permissive to the horn output then the horn will sound as soon as the button is pressed and sound for three two seconds bursts with two two seconds pauses between for a ten second time period. T4:0.ACC/0 toggles at a one second rate. You'll have to decide which one is better for you. I showed a two second rate in the example.

Great method, Alaric. If everyone used this for start-up warning horns, the overall stress level of employees could be turned down at least one notch.

jtashaffe, Do you work for DJJ if you do you now work for Nucor steel. If so PM me and I will give you all the help you need. Alaric rules and gave you a great answer to your question.