Program a Flip Flop Using One Shots. ONS, OSR, OSF in Allen Bradley's RsLogix 500

This is a popular request we get from viewers and is a great example to explain how one shots such as ONS instructions work.
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[@kevin00861]

Dear Tim, First of all i really cannot thank you enough for your amazing educational videos! Please keep posting more! The answer is that XIO and XIC input instructions that hold the same address would always reset each other, as in our Timers Lesson when you used DN bit XIO and the same DN XIC to make flashing timers or to recycle an output or to make a reciprocating / oscillator output. Again Dear Tim, thanks a million times !

[@joew4202]

I never get tired of watching your videos Tim!

[@TimWilborne]

Glad to hear that Joe!

[@clintathusaz]

Always happy when I find you've made a video answering my exact question in a very understandable manner. Thanks for your efforts!

[@TimWilborne]

Glad to help!

[@davidpalmer963]

Hey Tim , David Palmer here. Hope you and yours are well. Great detail on the logic ..switch on (logic high) switch off ( logic low).

[@TimWilborne]

Thank you David!

[@iliapopovich]

This is just a latch. Like an electromagnetic relay and I always tried to figure it out how to do it, now is more clear. Actually he is using the ONS and all the other elements to create logic gates. Well done.

[@TimWilborne]

Thank you!

[@3498137]

Hi Tim. Excelent explanation and it is very to apply in the real world. This is very uselful for controling a motor using the Stop an Start as a unique Pusbutton. I wonder how to use it like a Flip-Flop with independet Set and Reset. for example to control the sensing signals, low and high water level of a tank. Thanks for your excelent contribution>

[@shirwilbo2797]

Good teaching video.

[@TimWilborne]

Thanks!

[@tnapierism]

Can you please make a video about how to create the RSLogix 500 FFL and FFU instruction using CCW? Thanks!

[@TimWilborne]

I should look into doing a video on that, I'll put it on the list.

[@ankitbothra8205]

Excellent video..!! AB general instructions guide mentions "Unexpected operation may occur if : output tag operands are overwritten".. What does this mean??

[@TimWilborne]

It would be similar to duplicate destructive bits, see if this helps kzbin.info/www/bejne/g3iThmhpiLl3mLc

[@ankitbothra8205]

@@TimWilborne well seems it may be saying that indeed.. But I'd really call that expected output.. wouldn't you??!! Thanks..

[@anthonypessagno7048]

Great video. On my RS logic simulator I don't see a difference between XI and BIT. Can you help me with that or explain the difference. Thank you.

[@TimWilborne]

I'm not sure what you mean by XI and BIT

[@anthonypessagno7048]

@TimWilborne Thank you for the quick response. This probably isn't the best way to ask this question. I should have been more descriptive. Basically when I use the "user" tab or "bit" tab I get the same result. I don't see B/0 come up, I guess, for bit. If it's to much information involved....no worries. I am subscribed thank you for the videos.

[@TimWilborne]

What software are you in? I may have incorrectly assumed RsLogix 500

[@anthonypessagno7048]

@@TimWilborne It says Logix Pro 500 Simulator. I am new to this. I just figured with hitting the Bit tab it would automatically be a binary bit. Maybe there's more to it I have to learn.

[@TimWilborne]

Ah, it is a good tool but I don't have much experience with it.

[@jojoon1937]

I cannot find the link for rising and falling pulse video in the description

[@TimWilborne]

You can find all of our lessons at twcontrols.com/plc-lessons

[@dronai]

How can I use this concept to make an alternating relay ? Pump 1 and Pump 2 Alternating

[@TimWilborne]

In this situation you will usually have a stop, lead, and lag float. Each time the stop float goes down, you would do the flip flop. then if your toggle bit is off and the lead float is up then you would run pump one where is if the toggle but was on and the lead float was up you would run pump two. The lag float would turn both pumps on.

[@dronai]

@@TimWilborne I install these all the time, but I would like to build my own controller. The problem for me is the alternating relay. Looking at your program, I just made the flip flop work. Can't wait to try it out, Thanks, Dorian

[@TimWilborne]

@@dronai Great, let us know how it works!

[@rileycordell6749]

when i was in college we used internal flags on a software that was different to this and have been unable to locate on rslogix 500. do you know anything of this and if it is used in this software?

[@TimWilborne]

They would be bits or boolean such as B3:0/0

[@rileycordell6749]

@@TimWilborne thanks a lot. I’ll try tomorrow and comment how it goes !

[@MM-vi9kh]

Great

[@TimWilborne]

Thanks!

[@tongtanomwong2940]

Tim, I apply first program in the step by step with Micrologix 1400 . when I go to run mode it was FAULTED, shown Error description "Expansion I/O module 1 generated an error"

[@TimWilborne]

That means something is wrong with the module you have plugged in to the right of the PLC base. What do you have connected there?

[@tongtanomwong2940]

@@TimWilborne I have connected the Analog Module 1762-IF2OF2 A D 1,2.

[@TITANONICEvibes]

Can’t get it to work using rs5000

[@chadrickstephenson6064]

I get how the light turns on, but I don’t get how the light turns off when pressing the button again.

[@chadrickstephenson6064]

Oh get it. It happens so fast. Because of one scan the XIO’s are inactive to switch off the light.

[@TimWilborne]

Great, I'm getting ready to make a revised version with Studio 5000 and Connected Components Workbench.

[@ks1works]

How do you convert an OSR to an ONS when the follows a stack of different inputs? I am trying to convert a SLC 500 1747-L30A to a Micrologix 1400. I changed all of the OSR bits to ONS. There is a push button input that also acts like a reset button if you press it two times quickly. The ONS sets the bit and will not allow the reset function to clear the counter. Any Ideas?

[@TimWilborne]

The Micrologix 1400 supports the OSR. Why not stick with it? The issue is the ONS lacks the external output bit which your OSR is probably using elsewhere in the program.

[@ks1works]

When I converted the program to the 1400 and verified the program the errors indicated that the one shot rising was incompatible with the 1400.

[@ks1works]

should I do the conversion in RS Logix 5000 instead of 500?

[@TimWilborne]

@@ks1works I think you are right, let me look closer tomorrow

[@TimWilborne]

@@ks1works You are right. The Micrologix ONS is the equivalent of the SLC 500's OSR. It should work if you changed the instruction. My guess on why it wouldn't would be something different in the timing. How quickly did the push buttons have to be pressed sequentially? Did you verify the time bases and presets are the same in all of the timers?

[@kylesproductreview5583]

I would like to see bsl bsr

[@TimWilborne]

Hi Kyle, I'll put it on the list!

[@sprek2]

@@TimWilborne if you haven't made this video yet could you show some best practices for using an encoder with the instructions

[@TimWilborne]

@@sprek2 Good suggestion! We have this one talking about how to configure the high speed counter for an encoder. www.theautomationstore.com/rslogix-500-training-allen-bradley-micrologix-high-speed-counter-rslogix-500-function-file-configuration-for-an-encoder/ This one talking about calculating rate, speed, or RPM www.theautomationstore.com/rslogix-500-training-how-to-calculate-the-rate-speed-or-rpm-on-a-high-speed-counter-in-rslogix-500-for-a-micrologix-plc/ And this one talking about what happens if you don't have your input filters set right. www.theautomationstore.com/rslogix-500-training-what-do-input-filters-on-an-allen-bradley-micrologix-plc-do-and-what-happens-when-they-are-too-high/ What else should we cover?

[@stanleypolanco4887]

TIM GREETINGS How can I use OSF on an SLC 5/03 CPU. THANKS

[@TimWilborne]

Hi Stanley. It isn't available in the SLC 5/03. You'll have to get a little creative with the OSR instruction to take it's place. For example if you were using and OSF behind an XIC of I:0/0 then you would use an OSR behind an XIO of I:0/0 in place of it.

[@stanleypolanco4887]

@@TimWilborne It's what I thought but it would be a problem with the first scan thank you very much Tim

[@wshh8486]

Siemens already have an SR flip flop

[@TimWilborne]

Hi Charles. You are right, lots of PLCs have flip flops, but this exercise helps you better understand program flow. Thanks for watching!

[@CM-oy2kd]

Good job Mr. Wilborne. Where are you located

[@TimWilborne]

@@CM-oy2kd Thanks, the US

[@jasonvanhalle]

I think rung two is switching back and forth with every scan, so if it winds up off or on when you let off the button is just due to timing of the release?

[@TimWilborne]

Yes. One more thing to think about. Why isn't it blinking fast on the computer screen?

[@punder30]

Very good instruction and detailed information using a ONS instruction. I am sure some people call "/" a back slash but a majority if not everyone calls "\" a back slash and "/" a forward slash or just slash. en.wikipedia.org/wiki/Backslash

[@johnrece6622]

This one gives be the brain pain lol

[@TimWilborne]

Yes, I'm getting ready to make it for Studio 5000 and Connected Components Workbench. I've got some ideas on how to make this clearer.

[@jnrfalcon]

This video is the most confusing so far. I have no idea what ONS should mean and why it does what it does. And it is exactly what you choose to skip...

[@TimWilborne]

See if around 4 minutes helps you.

[@jnrfalcon]

@@TimWilborne it is the confusing part. As far as I understand now, ONS functions the same as OSR here, detects the action from proceeding element. If it changes from 0 to 1, send true downstream. It will send false if the proceeding element didn't change or change from 1 to 0. You did a good job on explaining what happened but didn't mention why. Like why does ONS output false when it receive a 1 while its storage has 1 already...

[@TimWilborne]

@@jnrfalcon We have a video in the works on the difference between an ONS, OSR, and OSF that would be helpful. Basically an ONS is the same as an OSR except the ONS passes true or false conditions onto the right of the rung for evaluation by an output instruction whereas the OSR is an output instruction that writes a one or zero to its output bit.

[@iliapopovich]

@@jnrfalcon The one shot (ONS) limits the basic scanning of the device (PLC), which is about 50 times per second in just one scan. That's because the electricity is moving almost with the speed of light and when you press a button ,even in the quickest way, the electrons did already 20-30 cycles and the desired output should be random and not the intended one. With One Shot you know that when you press it even for long the output should be only one scan or signal.