Thermostatic control of a linear actuator

Discussion in 'General Electronics Chat' started by robertazachary, Jan 28, 2014.

  1. robertazachary

    Thread Starter New Member

    Jan 28, 2014
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    My friends who purport to know cannot tell me how to operate a linear actuator with two limit switches using a thermostat. I hope to open green house vents with this. The problem seems to be that the thermostat is in a constant on or off. I, of course, don't know much about electronics. If someone knows or can point me in the right direction, I would appreciate it.
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    I proport to know too. However, without knowing your background, the details of the window, the details of the linear actuator, the degree your heart is set on using said linear actuator instead of a normal motor and gearbox, you budget, the time you are willing to invest in learning electronics (if any), and your reluctance to buying a commercially available mechanism among other things, I am not willing to start describing how to design your project to help you complete your task.

    I believe the previous sentence was one of the longer, yet nearly grammatically correct, sentences I have ever written.
     
  3. Nykolas

    Member

    Aug 27, 2013
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    I think there was a comma missing! E
     
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  4. robertazachary

    Thread Starter New Member

    Jan 28, 2014
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    I am an English major/teacher and that was a great sentence. I decided to go this route because the rack&pinion type of openers are very expensive. I tried to finds some from old warehouse window operators with no luck. Those using wax cylinders seemed fine until I was told I would have to replace the wax every couple of years at $100 a pop. My vents are 26" by 12' and weigh about 40 pounds. I came across some 24V dc actuators at Surpluscenter.com for only $45. That price is what is actually driving this quest. In the short term, I am afraid that learning electronics right now probably wouldn't work as I spend my spare time caring for my elderly mother. In the longer term, maybe. I was hoping to pass the information to my "purporting to know" friends to perhaps stimulate their interest. Thanks for the reply, I am encouraged that you think there is a way!
     
  5. #12

    Expert

    Nov 30, 2010
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    Did you say 26 inches by 12 feet?:eek:
    You are going to have to do something about sagging.

    I'll go get a drawing. BRB.
     
  6. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    No, but there is a missing "r."
     
  7. robertazachary

    Thread Starter New Member

    Jan 28, 2014
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    The vents are built on 3/4" square aluminum tubing with 1/8 wall. The skin is 28 guage
    corrugated sheet metal. It is on the north side and so does not need to transmit light.
     
  8. #12

    Expert

    Nov 30, 2010
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    Lacking some information, and assuming the thermostat can carry enough power for the motor (not likely), this is the basic concept. Fill in some information to get specific changes necessary.
     
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  9. inwo

    Well-Known Member

    Nov 7, 2013
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    Do yourself a favor and get an ac actuator with built in limits.

    Then you can connect it directly to a fan thermostat. (Sometimes called a barn thermostat) No other controls needed.

    They are designed to do just what is needed for your project.

    Line voltage, NO/NC, and a wide range or adjustable differential.

    I'll look at Surplus Center and see what they have.
     
  10. inwo

    Well-Known Member

    Nov 7, 2013
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    Is it this one?
    http://www.surpluscenter.com/Brands/VistaMounts/24-VDC-18-STROKE-LINEAR-ACTUATOR-5-1785.axd

    If DC is what you have, then you will need appropriate power supply, control relays, and someone who can follow #12's diagram.

    On the plus side it can be done with a standard low voltage thermostat, with a little modification.

    Rather than a posting frenzy, :) I'll edit with new info.

    Here is a 2 stage thermostat that can reverse a dc motor @3deg differential, by nature of it having 2 SPDT contacts.
    http://www.ebay.com/itm/PENN-CONTRO...030?pt=LH_DefaultDomain_0&hash=item4d0a765546

    And the specs for an A28.
    http://cgproducts.johnsoncontrols.com/MET_PDF/996238.PDF

    To allow for others input.

    Or you can use 2 A19s. One for open and one for close.
     
    Last edited: Jan 28, 2014
  11. #12

    Expert

    Nov 30, 2010
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    Am I that difficult?:D

    If thermostat = open
    and close limit = closed
    motor gets power from the right side of the drawing through the DPDT switches in K1 until the close limit switch opens.

    If thermostat = closed
    and open limit = closed
    K1 is activated and motor gets power from the left side of the drawing through the contacts in the DPDT relay until the open limit switch opens.

    Yes, every single part does something important. One mistake reading it and you're lost. It will work with AC power. It will probably need a relay or two as current boosters. That depends on whether the thermostat is a 15 amp Klixon or a 1 amp wall thermostat, and it depends on the current needs of the motor. It's a basic chicken coop design. Modifications available.
     
  12. inwo

    Well-Known Member

    Nov 7, 2013
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    Absolutely not!:)
    Very clear to me.
    That's how I'd do it.

    Things don't always read as intended. Sorry!
    It was a factual statement as to what he needs.
    In reference to OP statement.

    " I, of course, don't know much about electronics."

    Prompting, my search for a simple solution with no relays.
     
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  13. #12

    Expert

    Nov 30, 2010
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    Everybody sees a different way to do it, based on their experience and the contents of their junk box. :) That's why dozens of us help Other People. Somebody usually hits the combination that the Original Poster can understand.
     
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  14. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    You? I am not sure. But your drawings are fine.
     
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