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Author Topic: Shortcut to control 110v Linear Actuator with UNO? Need advice on next steps  (Read 1113 times)
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Ottawa, Canada
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Hi everyone, I'm pretty new to Arduino and anxiously discovering all it has to offer.

I have a basic idea on how to lay out my projects but hit a wall when it comes to choosing the right components (and doing so safely when it comes to things that plug into the wall).

What I'm trying to do is control a simple 12v linear actuator (no built in potentiometer) with my Arduino UNO.

See the attached image for visuals! -> http://i.imgur.com/iEM3coK.jpg

The 12v linear actuator is rated for 200lbs and it came with it's own control box and basic remote that plugs into the wall.

Instead of worrying about an H bridge or dc motor shield, I figure I can make use of the control box as the power supply, and hack apart the basic remote control and interface it with the UNO.

Where I hit a wall is how to rig up the circuit where the UNO can send the HIGH/LOW (UP/DOWN) commands to the actuator control box through the remote control input wires. The remote is very simple and the up/down actuation comes from just reversing the actuator motor's polarity.

The remote has 3 wires: UP/DOWN/COMMON.  I believe the common wire is the ground? Touching the UP wire to the COMMON completes the switch circuit and sends a command to the control box to move the actuator UP. DOWN wire to COMMON wire moves the actuator down. I believe there might be end-stop switches inside the actuator itself because it automatically stops the motor when fully extended or retracted.

When plugged in, the voltage across the remote's switch terminals is 17.3v.

Do I need a 2 channel 5v relay? Two single channel 5v relays? Two Transistors, and if so which specs? Diodes/Resistors? Any guidance on parts I need or circuit wiring suggestions is very much appreciated.

Budget isn't really a problem for the minor components.

The ultimate goal is to define the actuator's range in Arduino code (It extends 6" inches total) and make "presets" for different lengths of extension.

For example:
  • UP Button (hold it down)
  • DOWN Button (hold it down)
  • PRESET 1: Fully Extended
  • PRESET 2: Fully Retracted
  • PRESET 3: 25% Extended
  • PRESET 4: 50% Extended
  • Etc...

Since there's no potentiometer, should I add one into the mix (and how would one do that)? If so what is the best way to wire and code that in? Or could I 'guess' the position of the actuator by timing it (ie, 5 seconds of activation = 50% Extended)? I could see the latter being a problem if UP/DOWN buttons were used for manual positioning.

Right now I just want to control it using code...eventually I would like to have both physical switches AND 'digital' switches (for example from a web browser) that would control the presets.

Again I appreciate any help or criticisms...thank you!





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Have you testrun your INO file today?
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I'd go for two single pole relays. Each realy contact takes the palce of one of the buttons. When driving the relay coils from your arduino, use a transistor (example: http://www.kpsec.freeuk.com/trancirc.htm) and take the power from the 5V out pin. Its a bit "clunky" but very safe.

You have to have some "feedback" of the actuators position, as timing alone might be inaccurate if your load changes. It may be enough to have a contact at each end (max in or out) and time it from there. Otherwise I would place contacts at the desired stop points. Each contact takes an Ardunio pin and connects to ground. Use the INPUT_PULLUP setting on the pins. That too is a simple design but releiable/easily configure/check.
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Ottawa, Canada
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Thanks Msquare, I don't mind clunky! As long as it works reliably.

What do you think of this product for the relays?
http://www.ebay.ca/itm/390511068332?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Great idea about the contacts, I will do some more research. Thank you again for the tips.
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Who cut the wires on the remote? You probably could use a servo to push the two buttons on the remote.
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Who cut the wires on the remote? You probably could use a servo to push the two buttons on the remote.

Hi zoomkat, I cut them...not a bad idea! That would certainly make the coding a bit easier (for me anyway).

The the remote is a really simple circuit and could reassemble it if needed...I could maybe even replace the switches with something that's easier for servos to toggle. Thanks for your advice.
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A craft stick hot glued to a servo horn in a T fashon may be all that is needed. Servo centered the ends of the stick do not touch the buttons, rotate left and the left end of the stick pushes the left button, rotate right and the right end of the stick pushes the right button. People have done similar to operate the zoom rocker switch on the older camcorders. Dual nc/no switches are common in inexpensive toys (I've got a winch that uses the dual button setup for in/out control).
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Yeah really good ideas zoomkat. I also found a nice 100mm slide pot that I can attach mechanically for position presets.

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=261078424826

Thanks!
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Here's a really nice 3 position rotary switch that can be hooked up directly to the servo - cool!

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=121043185572
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Well, you're good at ebay smiley That last switch look like one of those that requires considerable force to switch - mostly to be safe. I am just guessing. but it would probably be too hard for a little servo. If you like the servo idea then get two simply micro switches and do some mechanical arrangement. It is a bit Goldberg like, so the relay is still simpler. I think those relay modules are OK.
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Could you post a picture of the label on the motor or copy the information on it over here ?

These actuators sometimes have an "encoder" wheel, that sends a pulse per rotation of the motor or its wormwheel driving the shaft.
If this one does not have that, you might be able to build it in yourself.
This would probably be better than to use a potmeter.
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Have a look at "blink without delay".
Did you connect the grounds ?
Je kunt hier ook in het Nederlands terecht: http://arduino.cc/forum/index.php/board,77.0.html

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Well, you're good at ebay smiley That last switch look like one of those that requires considerable force to switch - mostly to be safe. I am just guessing. but it would probably be too hard for a little servo. If you like the servo idea then get two simply micro switches and do some mechanical arrangement. It is a bit Goldberg like, so the relay is still simpler. I think those relay modules are OK.

Yes, love eBay  smiley Even if just to get an idea of what's out there.  I have some high-speed metal gear servos that might work...I guess we'll find out. What I'll probably do is try to mock up the relay method first...it would be nice to keep everything as electronically based as possible.
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Could you post a picture of the label on the motor or copy the information on it over here ?

These actuators sometimes have an "encoder" wheel, that sends a pulse per rotation of the motor or its wormwheel driving the shaft.
If this one does not have that, you might be able to build it in yourself.
This would probably be better than to use a potmeter.

Hi MAS3, to my knowledge there's nothing giving position feedback from this actuator...but I may be wrong. There are only two +/- wires coming from the unit.

I'd be open to seeing what's inside it - any idea what the encoder wheel part looks like?

It was a custom built actuator that I got in a clearance sale. Here is a close up of the label on it:


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Here's a really nice 3 position rotary switch that can be hooked up directly to the servo - cool!

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=121043185572

There is info below on how to use a radio shack rotary switch for reversing a motor via a servo.

http://web.comporium.net/~shb/switch.htm
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