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Temperature control with 2 setpoints

Created by: Lars wollsen at: 11/5/2014 12:05 AM (11 Replies)

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11/5/2014 12:05 AM	Rate (0)
Lars wollsen Posts: 5 Rating: (0)	Hi there I am trying to figuring out to control on analog(motor valve), with 2 setpoints, Normal temperature 20 celsius high temperature 40 celsius activated by a switch I have tried with 2 pi blocks but I can not connect 2 pi to the same analog output, What can i do ??
Lars wollsen Posts: 5 Rating: (0)
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11/5/2014 7:06 AM	Rate (1)
190B Platinum Member Joined: 2/8/2012 Last visit: 12/22/2014 Posts: 2347 Rating: (385)	Which LOGO! do you have? You can, if your LOGO! the block knows, use an analog mux. An example is appended. Attachment Setpoint switching.jpg (291 Downloads)

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This contribution was helpful to 1 thankful Users Lars wollsen

11/5/2014 8:19 PM	Rate (0)
Lars wollsen Posts: 5 Rating: (0)	hi there Thanks for the sulotions, i works great I am planning on buying logo 8, without the display, external display, 1 2 channel analog input for pt sensor, 1 2 channel analog output and 1 8 digital output module I have another question, I also need an anti freeze function on the same analog output, the antifreeze sensor is an digital indput, as long the input is active the analog output has set to max, even if all pi and analog function are turned off. This heat setup is for an ventilation system , where the old heat control unit i almost broke and no spare part, so want have program working before changing any control parts.
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11/5/2014 8:45 PM	Rate (0)
190B Platinum Member Joined: 2/8/2012 Last visit: 12/22/2014 Posts: 2347 Rating: (385)	So maybe something? Attachment Anti freeze.jpg (177 Downloads)

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This contribution was helpful to 1 thankful Users Lars wollsen

11/5/2014 9:09 PM	Rate (0)
190B Platinum Member Joined: 2/8/2012 Last visit: 12/22/2014 Posts: 2347 Rating: (385)	Or so... Attachment Anti freeze_2.jpg (170 Downloads)

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11/6/2014 10:49 AM	Rate (0)
Toeternietoe Platinum Member Joined: 12/27/2006 Last visit: 11/27/2023 Posts: 1192 Rating: (112)	The same way you select 2 setpoints (See example 190B: Setpoint switching) ) with an analog Mux. u can make it. Use the reference buttton. If there is an Frost alarm, then switch to a fixed value of 1000 setting in the analog Mux. Notice: LOGO! works internely with analog signals from 0-1000. So 0 would by 0V (or 0 mA) an 1000 would be 10V (or 20mA) an the analog output. So sending 1000 to an analog output wil result in 10 V (or 20mA) on thet output

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11/8/2014 8:30 PM	Rate (0)
Lars wollsen Posts: 5 Rating: (0)	hi there Tanks for the help. I have one last question, in the same setup with 2 setpoint and antifreeze. The analog input is pt100 room temperatur, is possible to add another pt100 that is placed inside the air supply channel, so that can you control the max temperature on the air that i blowed into the room.
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11/8/2014 9:47 PM	Rate (0)
190B Platinum Member Joined: 2/8/2012 Last visit: 12/22/2014 Posts: 2347 Rating: (385)	If I understand your question correctly: You ask if it is possible to change the set value for your control: Either the room temperature or the temperature in the supply air duct? If this is your question: Yes, it is possible.

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11/8/2014 10:40 PM	Rate (0)
Lars wollsen Posts: 5 Rating: (0)	hi again not quite, pt100 sensor 1 placed in the room, set to 20 degres, then i activate setpoint 2 40 degres, then the analog ouput(motor valve) turns to max to compensate for diffrent temperature, that may results i very hi flow through the heating coil, the fresh air tempeture that is blowed inside room may be more than 40 or 50 degreds, then i to want add a second pt100 sensor inside the ventilation channel to limit the air temperature, it make take more time to heat up the room, but it reduce the consumption from the central heating system.
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11/9/2014 9:26 PM	Rate (0)
190B Platinum Member Joined: 2/8/2012 Last visit: 12/22/2014 Posts: 2347 Rating: (385)	Can you upload your program?

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