How can I reset a bit?

That's right... I want to know how to reset a bit.

I feel kinda embarrased to ask this one, but I can't find the way to do it simple.

This is the situation:

I want to turn ON an output (pump) from a Touch-Screen HMI. I did all the programming into the HMI software and also on the RSLogix for the PLC, using a toggle button B1.

Everything is working fine, I push the button (B1) and the pump turns on, then I push it (B1) again and it goes off.

If I press the EMERGENCY STOP button the pump goes off, BUT when I release the E-STOP and RESET the machine, the pump goes back on without pressing B1 button.
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Now the thing is that the HMI turns a bit ON when you push B1. And it goes OFF when you press it again. But if the E-STOP comes on, while the bit is ON, it doesn't turn the bit OFF.

So I need to know a way to reset that bit whenever the E-STOP or RESET button are press.


I know this must be the easiest thing in the world but I'm burnout right now! LOL

Have a great weekend people!

Not sure what type of PLC or HMI you are using, but in an Allen-Bradley (and I expect others) you would just unlatch the B1 bit when the estop is hit. Assuming you have an estop trip input

E-Stop ......B1
-] [--------(U)-

I expect the only reason your pump stops is the estop drops out the control circuit.

Wally

Use the HMI bit to drive a one-shot.

Put an XIC of this one-shot in parallel with a PUMP XIC.

Between the parallel combination and the pump OTE insert an E-STOP XIO.

Now if the E-stop is activated the pump drops out and will not reenergize 'til E-stop AND HMI one-shot are true. Standard seal-in circuit.

Does the HMI have a momentary pushbutton capability? If so, that would work too.

Regarding latches: A-B (and others) caution against using latches on output image table bits.

In the image attached, I used the (U) instruction ( means bit unlatch).
In my example, the bit to unlatch will be the bit tag call B1. In your case, you must identify the correct address or tag name used in HMI to toogle the bit by means of B1 push button.

PS: I supposed that in normal condition (No emergency), the emergency input is ON, so I used the NC contact.