There is a very important difference between these two methods that we have a separate lesson on later when we talk about what a PLC does when you cycle power. Nearly identical to the functionality of A with a twist.Īgain I've only listed four methods but for me it comes down to method A or D. It is perfectly acceptable and functional. In beginners, this usually results in "spaghetti" code because they can "control" the output from multiple locations and won't fully be able to follow their code. We usually discourage beginners from using this method, but not because there is anything wrong with it. Usually this is done by pressing a screwdriver into the front of the contactor, a clear safety violation and very dangerous. This could cause more of a safety issue than it solves depending on the application but it will also lead to maintenance personnel bypassing all safety features to get the job done if they are not able to bump the motor with normal control. Right or wrong, maintenance personnel will intentionally hold the Stop Button so that the Start Button acts as a way to momentarily start the motor, with it stopping the moment they take their finger off of the Start Button.īy moving the Stop Button out of the branch and disabling this feature, it requires pressing the Start Button then the Stop Button to "bump" the motor. The ability to "bump" a motor for testing, lining up tooling, or maintenance. Yet it lacks a key maintenance feature that many motors need. This may be safer than Motor A's in theory and functions very similarly. I just said that the circuit and code should be designed with the highest level of safety in mind. Motor A's circuit with the Stop Button moved out of the branch.
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