Relay Timing Circuit

Help!
I have been looking for a solution to my timing problem all day, and finally came across this great site. Although it's not a PLC issue, hopefully some of you talented controls people can point me in the right direction.

What I have is a number of 8-pin 2PDT 120VAC control relays and adjustable on-delay timers that I'd like to use in a sequence. The order of events I'm trying to create is a sort of repeat cycle that uses three time periods: 5sec, 30sec, & 1min.

1.) Power is applied, starting a 5 sec. delay.
2.) Load A is then energized by a contact for 1 min.
3.) Another 5 sec. delay, during which Load A drops out.
4.) Then, Load B comes on for 30 sec.
4.) Another 5 sec. delay, during which Load B drops out.
5.) Back to line 2.
The cycle repeats until power is removed from the circuit.

After arranging relay and delay contacts on paper all day, my head is spinning. So, I think it's time to ask for some help.
I'm really hoping there is a way to do this using the components I already have. Maybe someone here can at least point me to where to find more info.

Regards,
Ralph Marotta

Do you have 5 timers and 2 relays?

This would be a cascading timer circuit. Authough there are just 3 time values you still need 5 timers.

Posts like this are why.

http://www.plctalk.net/qanda/showthread.php?t=28786

elevmike said:

Do you have 5 timers and 2 relays?

This would be a cascading timer circuit. Authough there are just 3 time values you still need 5 timers.

Click to expand...

Wow!
Thanks for the fast response.
Well, actually I have the components you listed.
But now I wonder if the circuit you have in mind would over-complicate what I'm actually trying to do.
I want to run a gearmotor using a vfd, for adjustable time periods in both directions.
I thought the 5 sec. delay would be useful to allow the motor to coast to a stop before reversing it......
Any ideas?
Regards,
Ralph

rsdoran,
I'm not an engineer, nor do I claim to be one.
A fruitless day of head-scratching is what prompted me to post here in the hopes that I wouldn't have to re-invent the wheel.
.......But I know I can!
After reading the first page of the thread you quoted, I think you are being a little heavy-handed here with someone new to this site, that you know nothing about.
Thanks for taking time out of your life to post nothing.

Ron may wrong, Ron may be right.

Either way, I respect his opinion, which he has a right to.

I completely understand his point of view.

And I can't say I have been nice to everyone over the years.

Traffic Lights anyone???

My thoughts are that a Micro PLC or a Smart Relay would be an excellant choice, at $100-$200. Programming should be less then an hour. Wiring should be less then an hour.

From a cost effective standpoint, you would not use parts that would require several hours to wire and spend all day trying to figure it out.

So, Ron would be right, 'specially since this is a PLC site!

Mike is very knowledgeable (READ "SMART"), too. He came up with the solution a lot quicker that I would have. But then, after a couple of minutes, I would have said PLC, if not sooner.

As many of us get wiser (READ "OLDER"), we get a little more impatient with the demands that are placed upon us. And also with the "New Breed" who are getting younger in age and experience.

Oh well, time to find something else to rant on!

What VFD are you using? - Usually you can get a zero speed signal from the VFD - may remove one timer for motor stopped

Some VFD's can be programmed to do what you asked without the external relays.

rmarotta said:

rsdoran,
I'm not an engineer, nor do I claim to be one.
A fruitless day of head-scratching is what prompted me to post here in the hopes that I wouldn't have to re-invent the wheel.
.......But I know I can!
After reading the first page of the thread you quoted, I think you are being a little heavy-handed here with someone new to this site, that you know nothing about.
Thanks for taking time out of your life to post nothing.

Click to expand...

Post nothing, was the link not informative?

What does 5 timer relays cost? A guesstimate (which will not be close to actual price) is $30 or more, the application calls for at least 5; which means at least $150 or more.

There are numerous plcs or smart relays, with free software or manual programming, that cost far less. I stopped using timers in many situations because they cost almost as much plcs.

It does not matter whether an engineer or not, that was the point of the other thread, you have a position similar too therefore this type problem should be simple and should look at the best solution.

A micro PLC like the AutomationDirect.com DL-05 or an A-B Micrologix would be a more cost effective solution than hardwired relays and timers. It would also allow future modifications and probably functions you haven't even thought of yet.

If you want to stay hardwired look at a programmable timer from Red Lion or Omron or such.

rmarotta said:

Wow!
Thanks for the fast response.
Well, actually I have the components you listed.
But now I wonder if the circuit you have in mind would over-complicate what I'm actually trying to do.
I want to run a gearmotor using a vfd, for adjustable time periods in both directions.
I thought the 5 sec. delay would be useful to allow the motor to coast to a stop before reversing it......
Any ideas?
Regards,
Ralph

Click to expand...

As Tom noted the DL05 would be less expensive & allow for future modifications etc.. The resulting program would be about 20 instructions so you could use the demo DS5 software for $free. If you want the operator to be able to adjust the timer values you could add a small HMI panel.

Also your drive should have the functability to give you feedback when the motor is at 0 speed. Feedback is ALWAYS better/more reliable then timing.

Or add a brake

rmarotta said:

I want to run a gearmotor using a vfd, for adjustable time periods in both directions.
I thought the 5 sec. delay would be useful to allow the motor to coast to a stop before reversing it

Click to expand...

Hi Ralph,

Before things get too ugly here... Any VFD is capable of handling direct reversing: It will automatically perform a ramp down before reversing. So, if the FWD signal is replaced by the REV signal, the VFD will ramp down first and then start running in the opposite direction. BTW most likely, if both inputs are active simultaneously the VFD will stop the motor.

So basically, you just need 2 timers for this project. You just have to add the ramp up/ramp down cycle time to the timers.

edit: ramp up = acceleration / ramp down = deceleration

Gentlemen,

Many thanks for your efforts, but I knew I was probably in the wrong place when posting my original question.
However, I do admire and respect all the capable talent available here.

All the responses so far seem to be leaning toward a more modern design approach that I am purposely trying to avoid. There are many reasons for this, but primarily I want this thing reliable, yet "dumbed down" to a level that most layman could troubleshoot.
No offense meant, but it seems I'm hearing some of the very reasons that cause others to complain about "over-engineering" a simple project.

Cost effective? As I said earlier, I'm trying to make use of simple components that are already on hand. The extra wiring time is not a problem.

For anybody that might still be following this:
In looking back over my original post I see some errors, so I'd like to revise the order of events needed.

1.) Power is applied.
2.) Relay A energized for 1 min. then drops.
3.) 5 sec. delay.
4.) Relay B energized for 30 sec. then drops.
5.) 5 sec. delay.
6.) Back to line 2.
The cycle repeats until power is removed from the circuit.
All three time periods are independantly adjustable.
Perhaps this might reduce the number of components required?

Thanks again for all your valuable comments.

rmarotta said:

Perhaps this might reduce the number of components required?

Click to expand...

I doubt it... You're still gonna get twelve responses that say to use:

one (1) PLC

(This is a great site, though.)

Sparkz,
Thanks for the suggestions. I didn't see your post until after I made my last one.
Again, for requirements not previously listed, I need this discrete timer circuit.
I'm using the drive's only built-in relay contacts to signal when the motor is at the commanded speed.
Another one of my reasons for the 5 sec. delay period is to prevent drive shut down when FWD/REV commands might appear at the same time.
Best regards