Beginner Question About Latching

ProgRambo

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Join Date
Jan 2017
Location
Hawaii
Posts
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Hi all. I have a beginner question about latching when using a single pole, single throw switch. In the attached image, I've hooked up a SPST switch to a latched bit. In the next rung, the bit is connected to a light. When the switch is thrown, the bit turns on and the light turns on.

My question is, how do you unlatch, or turn off the bulb by opening the SPST switch? Is it even possible? In other words, once I:1/0 is turned on and B3:0/0 is latched, is it possible to turn bit 3:0/0 off by opening I:1/0? I don't see how it's possible without involving another switch that's meant to break the latch.

Would appreciate any input. I hope the image is shared correctly. Thanks!

4FOVv


http://imgur.com/a/4FOVv
 
Last edited:
Ok, looks like I figured it out. Why even bother using the latch, just a straight switch will do the job.

I tried deleting the thread but couldn't find the option. Sorry for the wasted read!
 
Glad you solved it. Well done.
Next problem you will find you need to
Search this site for Flip Flop.
The answers are here
 
Most PLC designs use push buttons or HMI inputs.
These need to be latched or toggled on/off
By using a switch. How do you turn it off
If it's a motor start. How do you stop it.
 
logixpro

I have the same simulator as I just finished my degree, we constantly used it. Glad you figured it out, good luck in the future.
 
steelstud said:
I have the same simulator as I just finished my degree, we constantly used it. Glad you figured it out, good luck in the future.
Click to expand...

Am I reading this correctly.
You have used an SPST switch on a trainer to obtain your degree rather than programming some latching code.
Tell me I'm wrong please.
 
Lol, no it was a mix of that simulator, and then SLC 500's and 5000 with real world devices. But I understand your concern lol. I'm also a technician and deal with GE fanuc and DirectLogic so that helped as well. I just feel for the kid because I know how it feels starting out and recognized the simulator in the pic.
 
To answer how to unlatch the OTL for B3:0/0, you would use the unlatch instruction OTU addressed to B3:0/0.

Bubba.
 
Thank steelstud. I've programmed almost all of them.
Willxfmr. I try to guide not answer.
But I don't know what task he was given.
My thought was the flip flop cct. Usually given to students.
 
iant said:
Thank steelstud. I've programmed almost all of them.
Willxfmr. I try to guide not answer.
But I don't know what task he was given.
My thought was the flip flop cct. Usually given to students.
Click to expand...

I agree, but he did ask a specific question and showed his effort, so I didn't mind tossing him a bone.

Bubba.
 
Your fine. I didn't see the link from my phone.
Still not sure what he did finally.
 
Wow, every time I come here I'm so amazed by how active this forum is. This literally must be the best place for PLC discussions.

Great tip on using a stop button with an unlatching bit. This will come into play on the next part of the exercise I'm working on.

Thanks again. I feel like I need to close this thread like I close a Work Order when it's completed.
 
ProgRambo said:
I feel like I need to close this thread like I close a Work Order when it's completed.
Click to expand...

LOL.... they are open until they die of old age, then about two years from now someone will reply to your picture and say the link is no longer working and it will start all over because no one looks at the dates :ROFLMAO:

ProgRambo said:
This literally must be the best place for PLC discussions
Click to expand...

:site:
 

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