Author Topic: faster plc's?  (Read 10863 times)

hyperdyne

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faster plc's?
« on: August 09, 2002, 07:56:59 AM »
i am currently doing a project using dvt vision and a plc for sorting. the problem is that the AB micrologix that i am for the sorting routine is not keeping up with the machine. i am using a fifo buffer and have about 12 lines of programming for the machine. the software says it is running at 5-10ms scan time...but the scan time only shows up in 5ms increments.

i need a faster plc, anyone got any suggestions?
« Last Edit: December 31, 1969, 04:00:00 PM by 1076562000 »

support

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Re: faster plc's?
« Reply #1 on: August 09, 2002, 09:47:01 AM »
How fast do you need to sense the parts. is a FIFO buffer a bit shifter? That can be done quite quickly with the SHIFT command in the M-series PLC.  You can also use the interrupt capability of the PLC to sense the parts and execute the sort routine independent of the ladder logic scan time.
« Last Edit: December 31, 1969, 04:00:00 PM by 1076562000 »
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hyperdyne

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Re: faster plc's?
« Reply #2 on: August 09, 2002, 10:37:54 AM »
we have 3 possibilities, so i am using an integer type fifo register. using a bit register might be possible with multiple registers.

speed wise, we are sorting 1000 pieces a minute.
« Last Edit: December 31, 1969, 04:00:00 PM by 1076562000 »

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Re: faster plc's?
« Reply #3 on: August 09, 2002, 11:49:01 AM »
Bit shifting is very fast and you can shift as many adjacent registers as you like. E.g. you can contruct a 64 bit left shift of relay registers:

   LSHIFT RELAY[1], 4

you can also implement an integer fifo buffer using the DM[n] where n is an index.

  DM[N] = ....
  N = N + 1
  IF N > 10  
        N = 1       'implements a 10 position buffer.
  ENDIF  

For 1000 pieces a minutes it means about 16 pieces a second. It shouldn't to pose a problem for our PLC.

« Last Edit: December 31, 1969, 04:00:00 PM by 1076562000 »
Email: support@triplc.com
Tel: 1-877-TRI-PLCS