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Multiple timer

Created by: MadCat at: 8/18/2014 3:57 PM (15 Replies)

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8/18/2014 3:57 PM	Rate (0)
MadCat Regular Member Joined: 9/6/2012 Last visit: 2/19/2022 Posts: 25 Rating: (0)	Hi there, I have a question about the use of local timeres vs global timers. In my project i need to control 250 gates that have a set time to reache the endpositions. If the movement takes longer than the set time, I get an fault indication and the output for the motor is set to false. To make thinks easier, I have programmed a FB that contains the function. In the FB i have one S_ODT for the fault indication and one S_OFFDT for a delay switch off for the motor output. The delay is there, to make sure the gate has reached the end position. This I have for both directions. Now I'm looking for a way to minimise the numbers of timers used in the program. Any idea on how I could do that? Attachment Sample.pdf (462 Downloads)

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8/18/2014 4:15 PM	Rate (0)
William_B Posts: 5225 Rating: (1196)	Hi there, Look into the use of IEC_TIMERS. These will consume DB memory space what it will be better to use for your case. Which PLC and which TIA version? Greetings. w
William_B Posts: 5225 Rating: (1196)
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8/18/2014 4:35 PM	Rate (0)
MadCat Regular Member Joined: 9/6/2012 Last visit: 2/19/2022 Posts: 25 Rating: (0)	Hi William, as test I'm an S7-1511-1PN, the later system will be an S7-417; my TIA version is v13 with update 3. My problem is that we are normally using controllers form Phoenix Contact and there is no problem in the us of the FB's. There the timers are directly linkted to the FB and only used in the FB. Each time you use the FB, you give it a new name and the timer inside the FB only work in the current FB. I'm maybe a bit on the slow side here, but I think that the "timer issue" could use some work from Siemens. I mean, my section for the connection to our SAP application was easy, so why should it be so difficult to work with the timers? As descriped before, I have 250 material gates (24VDC motor) that can run in to to direction. Each movement is time controlled to prevent damages to the motor. If the set time is reached, I switch off the ourput to the motor and generate an fault indication. Under normal conditions, the movement takes 18 seconds before reaching the end position. If the end position is reached, I keep the output to the motor for 2 addional seconds to make sure that the gate is firmly set in to the end position. After that I switch off the output to the motor.

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8/18/2014 4:52 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 11/15/2024 Posts: 15402 Rating: (2446)	I agree with WilliamB regarding the use of instance DBs and local IEC_Timers for the S7-1500. For the s7-400, you need to use whatever option is available there as I do not recall seeing IEC_Timers as an option. To reduce the number of timers, you can either clock gates together with the same timer (not easy to time-sync gating, right?), or use physical timers, or perhaps use soft-start/stop motor controllers that ramp up/down for you. All at an added cost of course. Time or money or both. Me, I would go with W.B.'s recommendation and instance DBs and internal/local timer in the gate control FB.
	science guy
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8/18/2014 5:04 PM	Rate (0)
Jens_app Gold Member Joined: 1/5/2011 Last visit: 6/15/2024 Posts: 815 Rating: (123)	You could also use the CPU clock memory combined with an integer that holds your time value. If the way your 250 gates are controlled is identical, you could use one function in a loop to solve your issue. So loop+index combined with cpu clock + integer. Hope this helps Kind regards, Jens
	Keep it simple and on-topic. A simple straight-to-the-point answer is often of more quality than a complicated one.
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8/18/2014 5:07 PM	Rate (0)
MadCat Regular Member Joined: 9/6/2012 Last visit: 2/19/2022 Posts: 25 Rating: (0)	Hi huggy_d1, softstarter or so are out of the question. Two reasons for that: a) the motor is a 24VDC motor and b) the number of gates are just to much to install physical timers. Also the "gate" is more like a 2 way valve: one line in, two lines out. the gate is switching between the lines out. We are using blowers to transport materials from one silo to the other. The source silo can deliver materials to different destinations and there we are using those gates. Well, I can see the issue when using the S7-400 system were we don't have the IEC timers. I think it is a bit on the sad side that Siemens hasn't come up with an solution yet. I mean, the most complex systems are possible but the simple things are always a nightmare. For the S7-1200 and S7-1500 systems we got the IEC timers, so why not for the S7-300 and S7-400 systems? I hope that some one at the forum has an idea how to solve the issue. I have seen that there is an very active discution going on about the timer story but the ideas there are just to complex. I will be able to handel them, but I need also to think of my co-workers that are not that firm in the Siemens side.

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8/18/2014 5:15 PM	Rate (0)
MadCat Regular Member Joined: 9/6/2012 Last visit: 2/19/2022 Posts: 25 Rating: (0)	Hi Jens_app, the gates are controlled in the same way but at different times. The gates are always controlled one after the other. First when gate A has reached it's position, gate B will start. That is to minimise the max current in the switchgear. Each motor is using 2.0 A and a standard routing will involve up to 50 gates. Also are there so many combinations that the gates are using to reach the destination. As I have mentioned, there is an interesting topic on the question of the timers. I will have a look there as well to see, what sulution can be found. Your solution sounds interesting, but I'm having difficulties to visulize it for the moment. maybe that is because I'm now 36 hours at work.

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8/18/2014 5:32 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 11/18/2024 Posts: 5697 Rating: (715)	Hello, The 300 and 400 do have SFB4 & 5 (ton & tof) you can use them in a FB with multiple instance call (rightclick on the block, when dragged to the FB). So SFB 4 to check the running time and SFB 5 to do the closing trick. You find these timers in the system Functionblocks Library. If tha't not enough, create your own timer fb by using the clock memorybit and a counter. Regards, Marcjan
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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8/18/2014 5:36 PM	Rate (0)
William_B Posts: 5225 Rating: (1196)	TIA makes it crazy easy to use IEC timers for the S7-300 / S7-400.. as if for S7-1200. Please see the directions per JPEG. Attachment Visual clue_Multi instance IEC timers made easy for S7-300.jpg (498 Downloads)
William_B Posts: 5225 Rating: (1196)
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8/18/2014 5:51 PM	Rate (0)
Jens_app Gold Member Joined: 1/5/2011 Last visit: 6/15/2024 Posts: 815 Rating: (123)	Hi MadCat, I've attached an example. I wrote a detailed explanation, but my explorer crashed, so I will keep it brief. I have a configurable amount of water tanks(#AmountOfVessels), each of them equipped with a high level sensor. The high level sensor is of type normally closed and triggers an alarm after a configurable delay. I loop this function for the amount of water tanks that I have. FOR #index := 0 to #AmountOfVessels DO In this function I have 4 integers: 1) ClockCount hold the clock time (clock memory bit of 1 seconds increases that clock time) 2) a delay time before the alarm is triggered (T_HighAlarmTime) 3) StoredClockValue, which is equal to the ClockCount if no alarm is present and indicates the time the alarm is triggered when no alarm is present 4) AddedTimes which is the sum of the StoredClockCount and the delay time (T_HighAlarmTime) We compare the clock time with the time the alarm should be triggered (addedtimes). So when AddedTimes equals the ClockCount the alarm triggers. You can use this example for your case. Kind regards, Jens Attachment AttemptToExplain.jpg (467 Downloads)
	Keep it simple and on-topic. A simple straight-to-the-point answer is often of more quality than a complicated one.
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