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Old April 16th, 2021, 12:45 AM   #1
asteroide
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Arrow Eagle Signal MTA330A6 05 What kind of "PLC" or control is this?

Hello Friends

I need to replace this control with a PLC, I have not found info about this device. The only that I know that is a stepswitch.

This device is connected to some valves, sensors, and electronic timers.

Do you know How it works?

Any information would be appreciated.

Thanks in advance.
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Old April 16th, 2021, 01:51 AM   #2
parky
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By the looks of it, it's a cam timer the way it works is as it rotates the little tabs close contacts so for example on step 1 it may close contacts 1 & 3, on step 2 contacts 2 & 6 and so on, all it does on each step the tabs can be added to operate that output. Washing machines used similar things but the cams were fixed as per program. You will need to know the operation of the equipment but it is essentially a step sequencer. Not sure how it interacts with the motor perhaps it is capable of stopping rotation when a condition is met, external timers may then delay the motor to keep it on that step. Not completely sure but you can see where some cams have multiple tabs so that particular signal is on for a number of steps.
I would assume that the sequence is probably quite simple but reverse engineering it might take some time.
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Old April 16th, 2021, 06:38 AM   #3
drforsythe
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I got lazy and copied my response from the other forum:

I tried to find some info but could not locate manuals. If you have a model number, it would be helpful. I believe these devices are timers with multiple outputs. In the case of this one, it looks like it has 30 possible outputs and your system has 25 of those outputs wired. As the drum turns, the outputs turn on as the "flags" placed on the drum reach the actuation point (one spot along the drum where the individual switches are placed). This looks like an industrial version of a vacation timer for lights in a home to make it look like people are in the house. To convert this to a PLC, you will need to have or develop a wiring schematic that identifies which switches on the device control what devices on your equipment. Once you have that, you should be able to draw another diagram that identifies the relationship of each switch flag to each other, which will be time-based. If the unit still works and my assumptions are correct, it would be helpful to know how long it takes the drum to rotate one complete revolution. If you know that, you could determine the duration of each of the switches "on" time based on the number of degrees the "flags" cover. From there you could code your PLC based on the relationships you find with your diagrams. I would be really interested in seeing a schematic for your system if you have one. Good luck. That is definitely an interesting piece of early automation. A "keeper" for a collector, for sure! Good luck in your conversion. Please update this post with your findings.

Sorry, totally missed the fact that the model info was their the whole time!

Last edited by drforsythe; April 16th, 2021 at 06:41 AM. Reason: missed model info upon initial read
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Old April 16th, 2021, 06:55 AM   #4
drforsythe
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Here is a manual for a similar product. The part number callout may help you determine what you have even though it is a different series.

https://www.specialtyproducttechnolo...rsn=6b75f187_0
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Old April 16th, 2021, 12:07 PM   #5
OkiePC
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In the late 90's I replaced the "Tenor Steppers" with SLC 5/05s in each of two wings of 31 machines. I had 4 hours to yank the old and wire in the new and have it up and running. I got pretty good at panel wiring doing all that. Of course the first one took more like 7 hours to get fully debugged.

No more pegs, no more hung in a half step!

The one in your photo is much prettier and high tech looking than the antiques I had to replace.
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Old April 16th, 2021, 08:39 PM   #6
danw
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Heck, what's wrong with the original that new motor and some WD-40 won't fix? (I'm joking)
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Old April 16th, 2021, 11:10 PM   #7
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Of all the things we have to deal with on a daily basis I’m not sure wether to love this or hate it.
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Old April 16th, 2021, 11:28 PM   #8
drbitboy
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anyway, the replacement for it in a PLC is the SQO instruction, IIRC.
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Old April 17th, 2021, 10:21 PM   #9
asteroide
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Hello Friends

Thanks for your responses.

I think that, this is not a timer, it is a sequencer, because there are some electronic timers connected in this machine and I suppose are connected to this control.

I have not had the opportunity to review it on the floor but I have modified the photo that I have added with some annotations that I think they are.

At the upper left, main power, 120 VAC.
At the middle left, actual step number
It has 30 wheels, in the bottom 25 cables are connected, maybe inputs
At the right, 24 terminals, 20 cables connected, maybe outputs.

So, I think it is a sequencer, the wheels rotates and if the "input" is active then activates the "output". But it is strange, why 30 "inputs" with 24 "outputs"? If 1 "input" corresponds to 1 "outpus", what happens with the other 6 "inputs"?

The wheels have some numbers, I do not know what they mean.

I am looking for the diagrams, if these do not exist, I will have to create them.

I hope in this wheek to have some progress.

Thanks again.
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Last edited by asteroide; April 17th, 2021 at 11:16 PM.
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Old April 18th, 2021, 06:45 AM   #10
parky
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In a way it could be a timer but constant, if it runs then there will be a time between each transition, the numbers are just to show the step number you should notice that they all correspond i.e. at step 8 the ones that have the flag are all numbered 8 the external timers/relays etc. could be interlocks or time values, it is also possible that some of the timers disable the motor to hold it's position until a pre-set time there are many possibilities. I saw something like this many years ago, I was not involved in the replacement but the only way (without spending a long time trying to decipher it) was a logic diagram was provided & watching the system run with explanations from the operator, I believe the guy who did it had it up & running pretty quickly with just a few minor tweaks.
I suggest if you are the one replacing it then try to get the logic diagram, speak to the operator & glean as much information as you can.
I once converted a relay system into a PLC, however, we had no idea how it worked, we had a ladder diagram but many contacts/ relays were in the cold side of the ladder (not allowed in most PLC's) so in truth where the existing system used somewhere in the region of 50-70 relays the ladder in the PLC used something like 200-250 that included outputs and internal relays. but by creating the original ladder drawing but extra contacts i.e. no contacts in the cold side (ov line of the ladder) it worked & we found out exaclty how it worked.

Last edited by parky; April 18th, 2021 at 06:52 AM.
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Old April 18th, 2021, 08:34 PM   #11
Matthew Modar
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I replaced one of these last year. Here is a scan of the manual:

https://docdro.id/3puXVJ8

I just used this to help identify the IO wires and then rewrote the sequence from scratch. This was (obviously) an old machine, and the current owner did not use most of the old program. So it made more sense to start over than try to decipher the old sequencer operations.
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Old April 19th, 2021, 10:28 AM   #12
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Quote:
Originally Posted by Matthew Modar View Post
I replaced one of these last year. Here is a scan of the manual:

https://docdro.id/3puXVJ8

I just used this to help identify the IO wires and then rewrote the sequence from scratch. This was (obviously) an old machine, and the current owner did not use most of the old program. So it made more sense to start over than try to decipher the old sequencer operations.
I concur with this strategy. You can probably design a better control program by understanding the machinery operation rather than to decode what the wiring says it is supposed to do.
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