Override seal-in circuit

drbitboy · Jan 24, 2021

@parky it was not you who started it (but we all kept it going

): the OP called it a load, but labeled the output with an ---(M)---, so I don't think it was at all unreasonable where we went.

ASF · Jan 24, 2021

This is pretty standard start/stop/jog logic:

Code:

|
|   Start                    Stop             Output
|----| |----------------+----|/|----------------( )-|
|                       |  
| HMI_Jog_PB            |
|----| |----------------+
|                       |
|   Output     Jog_Cmd  |
|----| |---------|/|----+
|
|
|  HMI_Jog_PB                                 Jog_Cmd
|----| |----------------------------------------( )-|

As other posts have alluded to, pressing and releasing the HMI jog button while the motor is running will stop the motor on release. My practice has always been to require jog mode to be selected before showing the buttons on the HMI, and to prevent the jog command from doing anything at the ladder logic level if the motor is not in jog mode. Obviously, selecting jog mode will stop the motor as well.

(and yes, for the sake of simplicity, I'm going to assume it's a motor for now as well).

drbitboy · Jan 25, 2021

Instead of using the new internal bit to keep track of when a jog is active, there is also the alternative of using that bit to keep track of when the Start/Stop circuit is active cf. {Auto} below.

Code:

|
|   Start          Stop               Auto
|----| |------+----|/|----------------( )----
|             |
|    Auto     |
|----| |------+
|
|
|    Auto                             Output
|----| |------+-----------------------( )----
|             |  
| HMI_Jog_PB  |
|----| |------+
|

This offers a few improvements, IMNSHO:

The jog button does not stop a load previously running via the Start button.
Reads a bit cleaner.
Only 6/7 instructions, so it saves an instruction as well (but not everyone cares about code golf ).

[Update: whoops, I already did this in an earlier post]

Override seal-in circuit

drbitboy

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ASF

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drbitboy

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