Need help with GE Nano Logic

[diat150]

Basically all I want to accomplish is having any state change on any of the units 6 inputs turn on one of the outputs for 1 minute. so if input 1 is on, output 1 is on for 1 minute. if input 2 comes on while input 1 is on and counting down, reset the timer to 1 minute. Once input 1 goes off, start the timer. Essentially I want any state change to either start or reset the timer that controls the output.

I cant seem to grasp a good way to do this with GE. Id appreciate if someone could nudge me in the right direction.

 

[Steve Bailey]

I think an OFF-delay timer enabled by NC contacts from all six inputs in series would do it. The NC contacts should be one-shots.

The Off-delay timer in GE resets when the enabling logic is false. When the logic goes true the output turns on. When the enabling logic goes false the the timer starts timing and the output remains on for the preset time. Using the logic I described, each time an input turns on, it would interrupt the enabling logic for a scan which would reset the timer.

 

[I is a noob]

Ditto....

 

[diat150]

This is the only way I could come up with to make it work the way I described, where the output comes on if the input goes on or off. Anybody have a better idea than this? this seems to work great.

 

[Lancie1]

Diat,

I cannot tell from your description and your picture. I can't see if you have 1 output or 6 outputs (1 for each input). Your description leaves this undetermined, although reading it literally, it says "the output", which means there is only 1 output. Is that correct?

How many inputs are allowed to go on or off AT THE SAME TIME and what should happen in that case?

What happens to the assumed single Output: I understand that it should go off if the timer reaches 1 minute. But does it stay on as long as 1 or more Inputs are ON (AND Timer < 60 seconds)?

Essentially I want any state change to either start or reset the timer that controls the output.

Your logic appears to only reset the timer to 0 when any input changes states. But if no inputs change state, best I can tell, your Output will still be held on for 1 minute.

 

[diat150]

yes, just one output will be used. Yes, I do want the timer to be reset if any input changes state, and if more than one input changes while the timer is active I would like to reset the timer back to 0, so it starts a new cycle.

The only problem I see is if I have a chattering input. This would cause the output to always stay on. But Im not sure how I could remedy that since I need to capture both state changes.

 

[Clay B.]

yes, just one output will be used. Yes, I do want the timer to be reset if any input changes state, and if more than one input changes while the timer is active I would like to reset the timer back to 0, so it starts a new cycle.

The only problem I see is if I have a chattering input. This would cause the output to always stay on. But Im not sure how I could remedy that since I need to capture both state changes.

Chattering is a simple item to fix. If you use your actual input as the enable for a timer then you can set the timer to be larger than your chatter pulse.

I also recommend using a Time Off delay. Basically all inputs would have to be in the off state and once the timer completed the output would turn off. This would allow for inputs coming on and off during the cycle.

 

[Lancie1]

Yes, I do want the timer to be reset if any input changes state, and if more than one input changes while the timer is active I would like to reset the timer back to 0, so it starts a new cycle.

Still, what about the case where NO INPUTS change state? Do you want the output to still go on? The best I can determine, your exsiting program turns on the output even if NO outputs switch during the first 1 minute period. Is that what you wanted? Should not the output stay OFF until something happens?

I also recommend using a Time Off delay. Basically all inputs would have to be in the off state and once the timer completed the output would turn off. This would allow for inputs coming on and off during the cycle.

Clay, I tried an Off Delay timer with the LogixPro Simulator. Basically like you said it only works for 1/2 of the state changes (going ON). It misses the other half when inputs switch from on to off.

I think what this requires is 12 rungs, two for each input, one to detect the off-to-on transistion, and the second to detect the on-to-off state transition. Each of these changes need a One-Shot so that the logic only looks at the change in inputs, not the actual state of the input. After that, it should be easy to use these 12 "state" rungs to control the output and the 1-minute timer.

The problem is to get a detailed list of specifications giving exactly how the logic is supposed to operate. For example, if no inputs change within the first 60 seconds, should the single Output be on or off?

 

[diat150]

Still, what about the case where NO INPUTS change state? Do you want the output to still go on? The best I can determine, your exsiting program turns on the output even if NO outputs switch during the first 1 minute period. Is that what you wanted? Should not the output stay OFF until something happens?

Clay, I tried an Off Delay timer with the LogixPro Simulator. Basically like you said it only works for 1/2 of the state changes (going ON). It misses the other half when inputs switch from on to off.

I think what this requires is 12 rungs, two for each input, one to detect the off-to-on transistion, and the second to detect the on-to-off state transition. Each of these changes need a One-Shot so that the logic only looks at the change in inputs, not the actual state of the input. After that, it should be easy to use these 12 "state" rungs to control the output and the 1-minute timer.

The problem is to get a detailed list of specifications giving exactly how the logic is supposed to operate. For example, if no inputs change within the first 60 seconds, should the single Output be on or off?

yes, I do want the output to come on in the first 60 seconds. essentially what I am doing here is monitoring state changes to turn on a cell modem when a device goes into or out of alarm. So its a nice feature to have it come on automatically when the unit is powered up to "check in". Althought this could be accomplished by using the first scan and a move block I would think.

We do this to reduce the size of the dc system needed, since the locations that we monitor dont have ac power available. doing this will improve battery life by 1/2 to 2/3rds.

 

[Lancie1]

Basically, the method is to turn on an output. Then if any of 6 inputs change state, alternate the output between on and off. Now, where does the 1-minute timer enter the picture?

 

[RussB]

Basically, the method is to turn on an output. Then if any of 6 inputs change state, alternate the output between on and off. Now, where does the 1-minute timer enter the picture?

If I read the OP correctly, the output needs to stay on for 1 minute from the time any of the inputs transition to "ON". Which takes us back to post #2 by Steve Bailey.

 

[diat150]

actually my original post says that the timer needs to start any time a input changes. Ive accomplished that with the logic that I posted, but the only thing I havent had a chance to work on is putting in a deadband of some type that would work when a input goes on or off.

 

[I is a noob]

So you want Q1 to turn on if any of the six inputs change state? Q1 should stay on until there is one minute of time that none of the inputs change state?

 

[I is a noob]

Maybe this????

 

[mellis]

How about this...
Map the 6 inputs into a word, call it CurrentInputs.
Compare CurrentInputs with SavedInputs, if not equal reset the timer.
Copy Current_Inputs to Saved_Inputs.
The timer is always enabled.
If the timer is running, the cell modem is on.
If the timer times out, the cell modem is off.

Benefit of this approach is, it doesn't get uglier as the number of inputs increases.