One Input, Alternating two outputs, RSLogix 5000

[Robb B]

Hi Everyone, trying to get an alternating output to work. Read through the forums on flip flop, toggle, etc. Found this site http://accautomation.ca/creating-a-flip-flop-circuit-in-the-plc/ which seems to do what I want, but not sure about implementing it on control logix. I tried with ONS and a similar logic, but not quite getting the results.

Basically, one input (joystick button) needs to activate output 1 with the first press, and output 2 with the second press while cancelling the previously activated output.

 

[Tharon]

The example of the logic on that site should work. But for the ONS you'll need to create a bit.

 IN      BIT               ONS PULSE

-||-----[ONS]----------------(OTE)

Then use that OTE address and an XIC where they have the X0 Oneshot instruction. I don't think that instruction exists in ControLogix (or, if it does, I never used it, coming from 500/Micro platform).

 

[gclshortt]

+1 Tharon

http://www.plctalk.net/qanda/showthread.php?t=35790

The above thread explains the ONS instruction.

Regards,

 

[Lare]

ten different types

http://www.plcs.net/downloads/index...TERNATOR METHODS.pdf&directory=Allen_Bradley&

http://www.plcs.net/downloads/index...00&direction=0&order=&directory=Allen_Bradley

 

[daba]

Whichever "method" you choose, you must consider what happens to the toggled bit on processor restart, whether that is a power outage, or a processor mode-change.

Many of the examples will "reset" the toggled bit to a default state, and that may not be desirable.

My personal preference is to use a method that always remembers the state of toggled bits, and to program a specific reset of them if I don't want their state remembered through a processor restart. In other words, the programmer is making the decision, not the hardware.

I use a counter, driven by the "toggling" input. The counter's accumulator bit 0 will toggle on and off with each successive toggle input, and there's no need for a one-shot either. The counter accumulator will eventually "rollover" after 2,147,483,647 counts, but that is not an issue, it will count forever, and bit 0 will always alternate 0-1-0-1 etc. Just ignore the actual "value" in the accumulator. The counter is a "retentive" instruction, so the accumulator will always be remembered through a power-cycle or mode-change.

 

[Sydney]

My personal preference is to use a method that always remembers the state of toggled bits, and to program a specific reset of them if I don't want their state remembered through a processor restart. In other words, the programmer is making the decision, not the hardware.

I use a counter, driven by the "toggling" input. The counter's accumulator bit 0 will toggle on and off with each successive toggle input, and there's no need for a one-shot either. The counter accumulator will eventually "rollover" after 2,147,483,647 counts, but that is not an issue, it will count forever, and bit 0 will always alternate 0-1-0-1 etc. Just ignore the actual "value" in the accumulator. The counter is a "retentive" instruction, so the accumulator will always be remembered through a power-cycle or mode-change.

Great example, this is why I follow PLC.net, simple straight forward logic tips.

Regards,
Sydney