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  1. #1
    Below Par Bikernator's Avatar
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    Engineers/controls people...

    I am doing a senior design project right now and I've hit a bit of a snag. I'm a mechanical engineering student who hasn't taken controls in a while and need some refreshing. I've tried professors in the electrical engineering department but they were not interested and people in industry aren't as willing to help as I was hoping. Any help for this is not cheating or banned, this website as well as contributing members will be cited and listed under the references in my final report.

    Materials:
    2 electric linear actuators with limit switches which just stop the rod at the determined distance (i dont believe its an actual feedback signal)
    1 remote control and receiver
    Means of processing signal from remote receiver and delivering it to actuators (PLC or series of relays, i would think)

    What i need it to do is this:
    Press button on remote (prefer remote with only one button, but will use one with 2 buttons if necessary), actuator 1 extends, then retracts. Press button again and actuator 2 extends and retracts, repeat. The actuator will have a stroke of just around 2 inches, with required force of less than one pound. It doesn't seem hard but I have minimal experience with PLCs and i just can't get everything straight with the relays. And I know pretty much nothing about remote controls.

    Any help with this will appreciated. If you can refer me to particular products or part numbers I will be eternally grateful. Thanks again.

    -Brett

  2. #2
    The Site Administrator: Currently at home recovering from a couple of strokes,please contact my assistnt admins for forum issues Tom Stormcrowe's Avatar
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    You need to shoot Phantomcow2 a PM. Not kidding.....this sounds right up his alley.

    Quote Originally Posted by Bikernator View Post
    I am doing a senior design project right now and I've hit a bit of a snag. I'm a mechanical engineering student who hasn't taken controls in a while and need some refreshing. I've tried professors in the electrical engineering department but they were not interested and people in industry aren't as willing to help as I was hoping. Any help for this is not cheating or banned, this website as well as contributing members will be cited and listed under the references in my final report.

    Materials:
    2 electric linear actuators with limit switches which just stop the rod at the determined distance (i dont believe its an actual feedback signal)
    1 remote control and receiver
    Means of processing signal from remote receiver and delivering it to actuators (PLC or series of relays, i would think)

    What i need it to do is this:
    Press button on remote (prefer remote with only one button, but will use one with 2 buttons if necessary), actuator 1 extends, then retracts. Press button again and actuator 2 extends and retracts, repeat. The actuator will have a stroke of just around 2 inches, with required force of less than one pound. It doesn't seem hard but I have minimal experience with PLCs and i just can't get everything straight with the relays. And I know pretty much nothing about remote controls.

    Any help with this will appreciated. If you can refer me to particular products or part numbers I will be eternally grateful. Thanks again.

    -Brett
    on light duty due to illness; please contact my assistants for forum issues. They are Siu Blue Wind, or CbadRider or the other 3 star folk. I am currently at home recovering from a couple of strokes. I am making good progress, happily.


    . “He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”- Fredrick Nietzsche

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  3. #3
    Footballus vita est iamlucky13's Avatar
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    First of all, have you talked to your mechanical professors? I'd be very surprised if none of them knew enough about controls to point you in the right direction, and very disappointed in the school if you don't have a project advisor to give you a little more in depth help.

    A PLC is the most versatile way to accomplish this, although it can be done with relays. I think a couple of the relays will need to be the latching type, unless I'm just not being clever enough in my head. The ladder logic for a PLC won't need to be very complex. A couple hours learning from a decent ladder logic introduction should cover enough material for your needs. In the spirit of this being a student project and because I'm lazy right now, I will let you figure out the logic.

    Hobby stores are a great place to look for parts if your remote needs to be wireless. You just need a receiver that can either close contact to a PLC input directly, or be used to trigger an additional switch to close contact on the PLC input.

    Relays are simple. They're a switch that requires power. As long as there is power to the relay coil, it will hold the switch open. If you go the relay route, you will probably also need a couple latching relays. These close the switch the first time you feed them power, hold the switch closed when power is taken away, then open it again the next time you feed them power. You just need to know which terminals are for the coil, and which one's lead to switch contacts.
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  4. #4
    Mystery Meat gitarzan's Avatar
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    Quote Originally Posted by Bikernator View Post
    What i need it to do is this:
    Press button on remote (prefer remote with only one button, but will use one with 2 buttons if necessary), actuator 1 extends, then retracts. Press button again and actuator 2 extends and retracts, repeat. The actuator will have a stroke of just around 2 inches, with required force of less than one pound. It doesn't seem hard but I have minimal experience with PLCs and i just can't get everything straight with the relays..

    sounds like a door bell to me...
    Quote Originally Posted by Jseis View Post
    Is a ukulele player in a mandolin town and banned from all bars by the chief of police unless he leaves his strings and gravy at the front door.

  5. #5
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    doorbells sound more like "ding dong"
    "harder" is not a very good safeword.

  6. #6
    la vache fantôme phantomcow2's Avatar
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    What are you using to control the linear actuators? Step motors? AC motors? DC motors? Are they linear motors?

    I made a very similar thing to what you're doing for a play my college produced using a VFD. See if your drive has some external control mechanism (a response to a switch). For example, the VFD I used for the college responded to an opening and closing of the continuity between two terminals; opening the connection reversed the motor; opening another connection made it run forward; having no connections open stopped all operation. The opening and closing could easily be accomplished by use of a wireless relay, which you can find schematics for online and solder yourself.
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  7. #7
    getting bent Engyo's Avatar
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    A PLC would be easier, just because you can reprogram much more quickly than rewiring relays. That said, you just need to set up some latching circuits. Latch in the first one on the first button push, or even on first rod retract, and don't clear it until the second rod has retracted. Use this one to lock out the first rod from moving once it has retracted. Use the same thing in reverse for the second rod. With a PLC you could also use a counter setup instead of latching circuits if you prefer.
    Namaste, Engyo
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  8. #8
    la vache fantôme phantomcow2's Avatar
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    Yea, PLC is out of my area of expertise. I can see why people would say it's easier, but depending on what his control mechanism is, a discrete component setup is pretty darn simple. Wire the limit switches in series with the terminals of the controller (if applicable).

    What is your budget?
    Last edited by phantomcow2; 11-22-09 at 04:29 PM.
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  9. #9
    Below Par Bikernator's Avatar
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    Quote Originally Posted by phantomcow2 View Post
    Yea, PLC is out of my area of expertise. I can see why people would say it's easier, but depending on what his control mechanism is, a discrete component setup is pretty darn simple. Wire the limit switches in series with the terminals of the controller (if applicable).

    What is your budget?
    As it turns out, by simplifying the circuit to where one actuator extends while the other one retracts, it can be done simply using a relay. More simply, I found a transmitter that can operate two one-channel receivers with built in relays at the same time, by just staggering the receivers I get exactly what I want.... for $41

    Thanks for the offered advice, everyone..

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