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Ram function in PLC

Created by: Steven_Hoang at: 11/9/2011 1:50 AM (2 Replies)

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11/9/2011 1:50 AM	Rate (0)
Steven_Hoang Posts: 19 Rating: (0)	Hi my family, Now I have a problem need your helps, that is: PIW: signal input is supplied to AI PQW: AO's output, signal on AI will be converted to 4..20mA on AO's output. This analog signal (4..20mA) supplied to current to frequency converter (Speed) to control an engine. When producing 12mA on AO's output (corresponding to 1000Hz or RPM on converter's output). then engine speed increasing and reaching a value 1000RPM very quickly and in very a short time. Now, I want somebody's helps me to show a function in PLC which can control the speed slowly as soon as the current outut presents on converter's input (for ex: 20mA supplied to converter's input, then converter's output value is 1000rpm, it will increase (raming/ Ram function) from 0 to 1000 with a step = 100. (0 ...100rpm in 2second and then 100...200rpm in 2s, 300rpm,........, 1000rpm). Because I want to consider it like a real engine, when will start an engine, it will increase (Raming) slowly from IDLE speed to Rated speed (1000). Thank you in advance, Steven Attachment Speed_Control.jpg (34 Downloads)
Steven_Hoang Posts: 19 Rating: (0)
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11/9/2011 4:09 AM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 6/6/2023 Posts: 12036 Rating: (2595)	Hello Steven; I am sorry to say that the title of your post threw me off a bit, until I understood what you were looking for a "ramp" function to output an increasing value to your analog output channel. You could easily build a step function, just as you were starting to describe, by using timers (or a cyclic OB)and an increasingPQWxxx (using an ADD_I instruction, for example). However, every time you would want to change the parameters of your function (such as the ramp-up time, or creating a ramp-down) you would have to modify the function itself, or introduce variable parameters. This would make the overall program more complex. Now Siemens provides a sample function that you can use in your own program, once youstudy the provided description. You can download it from this link: http://support.automation.siemens.com/WW/view/en/1853767 Notice there is also a WinCC project attached that you can also use, if you happen to have the software. Hope this helps, Daniel Chartier

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11/9/2011 11:31 AM	Rate (0)
Steven_Hoang Posts: 19 Rating: (0)	Hi Dchartier, I'am sorry for the title made you confuse. It's my wrong misspellings Thank you, Steven
Steven_Hoang Posts: 19 Rating: (0)
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