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Bill Estey

PLC outputs syncronize

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Hi I am working on a control system that will have outputs that operate on time how can I make these outputs operate so they will not be syncronize.I want to be sure that when these turn on the load the contacts won't close at the same point in the power cycle. Thanks for any input on this question

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Do you want to just make sure that no two (or more) outputs go on during the same program scan? If so use a DIFU set to comes on with each output. Use a not "the DIFU" bit to blank the other outputs for one scan. Set the outputs to make sure then don't go off as others go on. If that's not what you want, what do you want?

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Many ways to skin a cat, you could just create a drum type sequencer, number of steps = no of outputs, only 1 output can be enabled at a time, based on the time between steps.

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Sorry for the late reply I have been away.What I am looking for is I am turning on these outputs every 3 seconds and I want to be sure they don't always turn on at the same point of the AC sine wave so every 3 seconds but with a bit of radomization.

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when you turn on a output then set a bit on to inhibit turing on more outputs. Reset bit after a short time.

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Use DC Scan time will not be that consistent will it? What is the problem you are trying to overcome? Would zero switching solid state relays help?

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The potential problem I am trying to overcome is having my outputs turn on a contactor at only one point of the power sine wave I would lime to have this happen at random points of the ac sine wave

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From another angle: What would happen if the outputs switched at the same point in the sine wave?

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A contactor implies a relatively large electro-mechanical device to me. If so, I am sure the energising response time could easily be as long and potentially even longer than the cycle time of the sine-wave (assuming a 50/60Hz wave which gives a cycle time of 15-20ms). The coil could be energised by an output and it would give largely random timings for which part of the sine-wave it operated I am sure. Hope I have understood your problem correctly, as I made a couple of assumptions. Andy.

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