Making a device to push a button via remote

Discussion in 'The Projects Forum' started by absoluteZro, Nov 12, 2011.

  1. absoluteZro

    Thread Starter New Member

    Nov 12, 2011
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    Project goal:
    Open my dorm room door automatically using the handicap system already in place.
    There is a common blue button inside my dorm room that opens the door when pushed. I cannot rewire the system, since it is a college dorm (and I would be completely lost/that would be a bad idea).
    So the idea is to make a device that will push the button for me. This way, if I am outside my door, I can open it without my key.

    Here is the part I need help with. I would like to design this by myself so I can learn all about IR, RF, circuitry, motors, dc, ac, and whatever else comes my way. Before I start buying parts though, I would like to find out if I am completely off my rocker in terms of the direction I plan on going in.

    The Plan: buy a relatively weak dc motor from ebay/amazon that will run off of no more than 2-4 batteries. Maybe buy two weak motors to work in tandem pushing on the same spot. Use some gears to convert that motor rotation into a push on a specific spot. The handicap button does not need to be pressed in the center, in fact it is easier to press it near the corners (it has four activating points, one in each corner, all of which open the door independently from what I can see). I will probably need to find a way to get this device to stay put on the button. Maybe I will have to use a clamp, or as a last result, drill it to the wall.

    So is this a really dumb way of achieving my goal, or should I start buying? From what I can tell, the force required to activate the system is actually quite larger than I initially expected. Assuming the force is the same as most public handicap buttons need, do you think a cheap $5-10 motor would be able to cut it? I'm having serious doubts. Also, would taking a bunch of motors from computer fans give me anything usable?

    As is probably obvious from this post, my knowledge of all things electrical is close to nothing, sadly. But that is why I really want to go through with this. Once I get something that works, then I will worry about the IR or RF and stopping the device after the door is open.

    this is the kinda button I mean if it is unclear:http://image.shutterstock.com/displ...13,1/stock-photo-handicap-button-14527534.jpg
     
    Last edited: Nov 12, 2011
  2. iONic

    AAC Fanatic!

    Nov 16, 2007
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    I'm thinking rubber mallet with a hole drilled at the bottom of the hammer. With a pin inserted in the hole you could use a bracket to fasten it to the wall. The remote would control the release and gravity might do the rest. You could at least buy the mallet and try it holding it with two fingers and see if it's the force you require or not, if not, return the mallet. If it works you could move on to the next phase of the project, hot to reset the mallet inc ase of a misfire (Motor and fishing line...)
     
  3. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Ok, you cannot rewire the system, but can access the button wires? It would be MUCH easier if you could for example put a relay contact in parallel with the button wires.
    If we knew the button model # maybe we could find out if this is an option?
     
  4. absoluteZro

    Thread Starter New Member

    Nov 12, 2011
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    After seeing a thread in the projects section about lifting things, I also thought gravity and momentum might be my best friends. The original idea is definitely scrapped.

    I think this new one might be harder circuit wise, but it will probably be faster to build. Less moving parts means less problems later!

    So Testing with a ~2lb weight brought to about 45º opened the door easily. Proof of concept: check.

    I will work on a design and then figure out what the circuitry will need to accomplish.

    Also, yes praondevou, I can access the wires, but there is very little hope in finding out the model # of this system. There are two security lock looking things outside my room. After opening the wire box in my room, it appears that those two systems (one is one of those things where you swipe your key and it opens, the other looks like a combination lock), have the wires exposed. The button's wires are not exposed. They go straight up to the system above the door. I would probably be more open to playing with the wires, but my roommate is adamantly against it. I don't want to start anything with him.

    I'll stick to an external system.
     
  5. praondevou

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    Jul 9, 2011
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  6. absoluteZro

    Thread Starter New Member

    Nov 12, 2011
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    it's been a while since I had calculate the force of anything other than fluids and gasses. If I have a 2lb (grrr english units!) mass at the end of a 7inch rod, released at 45º, how will I calculate the force at the bottom of the pendulum swing? If I have that number, I can compare it to the pusher I buy (I did not know they had those, saves me sooo much time building when I need to be working on the control aspect).

    That pusher says this: 1mm, 100gf | 3mm, 27gf
    Erm, is that grams force or something? Never heard of gf....or is that ferrets?

    I don't really understand how it works. A current is sent through the solenoid, but how does it push the armature/why does the armature move?
     
  7. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Yes that's grams force. 100gf would be 1N. I hadn't seen the specs. Looks too weak to me now.
    Would be interesting to know what force exactly is needed to push the button.

    Btw, it works like THIS.
     
  8. absoluteZro

    Thread Starter New Member

    Nov 12, 2011
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    so what about 8N? I really can't put newtons in perspective. Learning outrageous problems in physics didn't help much.

    So 1 N = 1 Kg * m/s2 ....great :/

    If I were to use a scale to push on the button, and recorded the mass at which the button activates, how could I calculate the force? I wouldn't know the accel.

    Grr science!

    Back to the 800gf 10mm pusher. Only Issue I see (besides blowing $16) is that it is 24v 1.84A...where am I gonna get that kinda voltage for pennies. No where I'm assuming.
     
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