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Old September 16th, 2020, 03:46 PM   #1
salman101
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Digital counter display wiring to the output terminal

Hi, I am using rather an old PLC (FPO-CT32) by Panasonic with FPWINPRO 7. It doesn't give out the option of activating a high-speed counter for the output channels. On the input side (X) I have attached a rotary optical encoder and using the high-speed counter channel as input from the encoder (which is a pulse train). After each complete revolution of the encoder shaft (500 pulses), I want the digital counter to display the count i.e. 1,2,3..and so on. I have developed the logic in the program but how do I use/interface the output channel (Y) with the digital display counter? I am using the basic digital display GDD797949AT (24-28v) with a six-pin connection on the back (2 pins for reset, 2 pins for supply, 1 pin for the up count, and 1 pin for the down count). Thanks
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Old September 17th, 2020, 03:00 AM   #2
parky
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The only way I can think of on such an old PLC is to pulse train output, however, as I doubt that this model has high speed update of Peripheral outputs then you could only pulse the output at the rate of twice the scan time. So assume a scan time of 100ms then you could only pulse every 200ms, so 5 pulses per second, so 500 would take 100 seconds. even if the scan time was as low as 50ms it would still take 50 seconds. The only other way would be to use 7 segment displays and either use 16 outputs for a 4 digit display or if matrix type 8 outputs for BCD data & strobe. As the Panasonic is based loosely on the Mitsubishi FX it may have functions to convert integer to BCD and even BCD to 7 segment, however, the outputs required would depend on the digits required.
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Old September 17th, 2020, 10:06 AM   #3
salman101
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Thanks, Parky. It does have function blocks to convert INT to BCD to 7-Segment. Input to the PLC (at X0) is the pulse train, which I am counting with the HSC counter at the input side. After counting 500 pulses at the input, my counter in the software goes up by 1 integer. I want this count up to show at digital counter through one of the output channels (Y0,Y2...). (I think digital counter is different than 7-segmetn as, for example, it has one pin, which ups the counter by 1 when triggered, and the other pin vice versa) . I don't know how to send a trigger signal/display signal to the output channel when a certain number of pulses (500 pulses) have elapsed on the input side (as I had been using output channels just to turn on/off motors/processes, or send pulse trains, etc, and not to display anything)

Last edited by salman101; September 17th, 2020 at 10:24 AM.
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Old September 17th, 2020, 11:51 AM   #4
parky
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I assume you want to increment the display every time the high speed counter reaches 500 (I assume it is then reset) providing the count to the display is less than the scan time of the plc x 2 i.e. every 200ms then it is quite simple.
The logic in the pic is a simple example in Mitsubishi (should translate into Panasonic).
The first rung is just my simulation of the High speed count using a normal counter and 100ms pulse M8012, You will have already set up the HSC counter (C235 I assume). The next rung is the compare for greater than or equal 500 this sets the output that drives the display. and resets the HSC back to 0.
The next rung uses the output to start a timer for the pulse time.
When this timer finishes, it resets the output i.e. you get a pulse of 200ms (k2) you may be able to reduce this depending on the scan time and pulse length needed.
Just for testing and as verification of the display the final rung increments a register so that you can see what the display should be reading.
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