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Old March 11th, 2004, 03:46 PM   #1
Anibal Hernandez
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What is the best way to send 4 signals to a counter?

What is the best way to send 4 signals to a counter?

On a Micrologix 1000 I need to show 4 counts on every cycle of the press. That is every time the press comes down and up the counter must be counting by fours.

Assuming Machine is turned ON for the first time and the counter is reset to zero, first machine cycle the counter is 4, the next machine cycle the counter is 8, then another cycle completes and the counter is 12…. So on and so forth.

What is the best way to send 4 signals to this counter? This is a regular counter that increments every time a pulse is received.

Andy
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Old March 11th, 2004, 03:55 PM   #2
Allen Nelson
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For ideas...

See THIS THREAD
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Old March 11th, 2004, 05:26 PM   #3
chavak
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Another counter method -
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Old March 11th, 2004, 07:20 PM   #4
Anibal Hernandez
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Allen Nelson:

Thanks for the link, it really helped a lot.


chavak:

The application call for a real hardwired counter. Your suggestion will work great for an internal one.

Thanks guys

Andy
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Old March 11th, 2004, 11:16 PM   #5
Lancie1
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Andy,

I think you are talking about a physical counter, instead of a PLC "software" counter like most of use here on a PLC site would assume.

To change one count into 4, you would have to have a circuit board that takes 1 pulse and converts it to 4 pulses (a pulse generator, pulse extender, or pulse stretcher). There are such solid state devices, and I am sure someone here knows how to build one from scratch. I used to know that, but have forgotten much of electronics design.

You can of course take a low-end PLC and put 1 pulse in and get a rapid 4-pulse output, using some software timers and relays. Thay may after all be your easiest solution IF you have to keep the existing counter on the existing machine. If you can change out the counter, you can probably find a BCD (Binary Coded Decimal) counter that can be wired to count by 4 instead of 1.

Last edited by Lancie1; March 11th, 2004 at 11:19 PM.
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Old March 12th, 2004, 04:33 AM   #6
Anibal Hernandez
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Thanks everyone for the answers.

I resolved the issue with 3 TON and a One Shot instruction. This Forum has to be the best there is, very knowledgeable members who are eager to help.

Andy
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Old March 14th, 2004, 05:27 PM   #7
chavak
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Andy,

You got your logic to work, that is important.
But, you mentioned 3 timers and a one shot. So thought of posting another method. Just for your reference.
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Old March 14th, 2004, 05:43 PM   #8
Anibal Hernandez
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chavak:


I love your solution, like it so much that I will use it in my logic.
Sometime I'm just amazed at the many ways you can achieve basically the same result with so few rungs.


Thanks
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Old March 14th, 2004, 06:06 PM   #9
Anibal Hernandez
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chavak:


I noticed you are using a Constant value in the LIM instruction. Wouldn’t' you get an error.

Don't you have to compare to a Word instead of a Constant?

Andy
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Old March 14th, 2004, 08:10 PM   #10
Doug-P
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Quote:
Originally posted by Anibal Hernandez
chavak:


I noticed you are using a Constant value in the LIM instruction. Wouldn’t' you get an error.

Don't you have to compare to a Word instead of a Constant?

Andy
No. Constants or memory locations are acceptable arguments for LIM instructions. You can also use indirection and I'm pretty sure indexed addressing is also legal.
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Old March 15th, 2004, 12:01 PM   #11
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All of this might work for press application but depending
on specific needs it might not be best solution.
Why count by 4? Because press makes four parts with each stroke?

A while ago I was doing something similar where machine
had two stations. Both were running same process but
running completelly independant from each other.

Customer wanted ONE external counter to count all parts
produced. The problem was that we wanted perfect result
while stations were not synchronized in any way.
In other words "Part_Complete" signals could happen at
any time (even at the same time or with very little delay).

Solution was to use one shot from each "Part_Complete" to
increment internal counter but only if the other one shot
was off. If both were on, increment by two.

Then there was a rung that was generating pulses for the
external counter. This would run while the internal counter
was not equal to zero. Every outgoing pulse would also
reduce accumulated value by one.

Just a tought...
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Old March 15th, 2004, 12:09 PM   #12
Anibal Hernandez
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panic mode:


I appreciate your thoughts. This is only one station small press machine with 4 knives lowering along with the Ram and cutting flashes-spruces out a plastic molding part. The way chavak suggested it would work just fine.

Thanks

Andy
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