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Thread: Suggestions on a servo or actuator?

  1. #1
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    Suggestions on a servo or actuator?

    I started a thread about my Lenovo A1107 tablet in the Android section a couple weeks back and have received plenty of useful feedback. I've come to the realization that its a turd of a tablet and I could do better with another product but.......it was cheap (got what I paid for) so I'm gonna try to salvage it.

    The problem (one of several) is I've tried several automation apps including tasker and others to put the tablet to "sleep" when parked. I put the tablet into airplane mode and shut the screen off. When "waking" the tablet up, bluetooth does not stay active. It comes on and shuts right off. This seems to be a known issue with this tablet when coming out of airplane mode. So my thought is to power the tablet down and restart it when I need it. I still have a separate stereo in my vehicle for audio.

    I need suggestions on using a servo or actuator to tap the power button on and off. I have experience with RC car servos but I don't want to over think this if I don't need too. With standard RC servos, they would need some type of controller to move the servo. I would have to program a controller to mimic the pressing movement for a specific time and then program it to return to center. It there an easier way to just get tap or plunger press from something similar?

    As usual, all suggestions are most appreciated!

  2. #2
    Super Moderator. If my typing sucks it's probably because I'm driving.... turbocad6's Avatar
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    you could rig up a door lock actuator to push the button, also I did one once with a spring loaded bar that sat above the switch behind the dash, just reached in above the screen and pulled the bar to push the switch. there are a lot of ways to do something like this but a solenoid type actuator like a door lock actuator should be cheap and relatively easy

  3. #3
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    Look at a time delay relay.

  4. #4
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    If you don't mind taking the tablet apart you could just wire an external switch on it or put a relay across the contacts.

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    Thanks for the feedback....

    turbocad6: I thought about the door lock actuator and looked at the one parts express sells. My hesitation was in trying to find a way to rig the action. The power button is on the left side of the tablet and I figured by the time a fashioned a bar for the switch, a linkage and a bracket for the actuator I might run out of room. And if memory serves me correctly, door lock actuators are pretty loud. I'll investigate that further as that might be the way to go.

    redheadedrod: I thought about an external switch but the way the switch is soldered to the board, I don't think that's gonna work. I looked at it briefly last week. I'll take it apart again to confirm; that was my first choice for a solution. I've always liked Lenovo products for how easy they are to repair and how readily available parts and maintenance manuals are.

  6. #6
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    you could use a micro linear actuator (sometimes called a linear servo) to press the button for you, wire it to a momentary switch that you mount wherever you want. you probably won't find a 12v one, but there are 5v ones that could use the same power supply that the tablet is using.

    edit - actually the simplest thing is probably a 12v electromagnetic plunger or linear solenoid. not sure if this one has enough force, but you get the idea: http://www.ebay.com/itm/7mm-Stroke-D...21057916600%26
    Last edited by theksmith; 03-27-2013 at 05:19 PM.

  7. #7
    Super Moderator. If my typing sucks it's probably because I'm driving.... turbocad6's Avatar
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    a door lock actuator is an electromagnetic plunger, it can be wired to either push or pull and it will have at least an inch of travel if not more and can be had for like $5-$10 to your door. if it's too strong and too loud you could run it with less voltage. also you could remote mount the actuator and run the switch activation with a cable, like a bicycle brake cable/shift cable, etc... you could also wrap the actuator with foam and/or damping material to make the click quiet. you could also counteract the forces and dampen the actuation with a pre-loaded spring against the activation action. there is no install that this will not be able to fit since the actuator can be mounted remotely and in most cases this will be easy to rig up. this is assuming you don't want to open and modify the tablet itself, and you want to keep it easily removable and swappable.

  8. #8
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    Since you know R/C servos, reshape the linkage wheel into a cam to bump the switch.

  9. #9
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    The only problem I can see with using a door lock actuator is that it would need to actuated twice each time..... once to push and once to retract/release, otherwise it will just push and hold the button. A hobby servo with a cam would run into the same basic problem as the dl actuator in that the cam would have to go from low to high and back to low, but would also need to be reversed for the next press unless you used a continuous rotation servo. I would try some sort of spring loaded solenoid that would allow the spring to retract the plunger once power is removed. Do an ebay search for "linear actuator push" and see what is available. You would probably want to put some padding or spring dampening on the end of the plunger so it would not literally "hammer" the button.

  10. #10
    Super Moderator. If my typing sucks it's probably because I'm driving.... turbocad6's Avatar
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    no, a door lock actuator is a free floating plunger when not activated, otherwise it would prevent you from manually locking and unlocking a latch, it's not like a linear actuator or servo. all you need is a single electrical pulse and maybe a light spring return. there are smaller actuators that do the same but not as convenient to locate and cheap. for example most modern cars have the actuator built right into the door latch assy, so the electro plunger is very compact in comparison. if you got your hands on a door latch from say a Honda or chevy or most modern cars then you'd be able to remove the electro plunger from it and use that. older carbureted cars used a small electro plunger to manually kick the idle higher on a cold start, that could also do well and I've used those to start up older Toughbook installs that had a slide switch for on/off .


    then there's the trunk release solenoid, also an aftermarket alarm add on and cheap but you'd have to def use a linkage design to convert the pull to a push... it too will either be spring return or free floating plunger when not energized


    you may also be able to find other smaller 12v electro plunger style actuators too I'm sure, but the common cheapo door like actuator that you can get on ebay is quick easy and cheap and comes with a ready mounting solution and remote mounted cable actuated means the size may not be a problem. with some searching I'm sure you could find something smaller too and have it directly actuate instead of having to remote mount it with linkage or cable
    Last edited by turbocad6; 03-28-2013 at 10:16 PM.

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