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Hi, I'm working on a robotic hand for my science fair project. The idea is that if their are 15 joints on the human hand (3 on each finger, this is counting the one at the knuckle.) the amount that your fingers can flex naturally without force against them is 180 degrees, having less joints activated (in the code) would reduce the flexibility of the fingers themselves. For example, if the joint at the knuckle is deactivated (this would all be done software side) then only the middle and tip joints would be able to move at once. I would use a LilyPad Arduino USB as this particular Arduino would fit in your palm (at 2" in diameter this is plenty of space to be attached to the center of the hand) and several servos would power the joints. Deactivating these servos would deactivate a joint or two, depending on how much is powered.

Additional Questions.

Would there be any kind of splitter available for a servo? So that several joints could be hooked up to one servo, reducing the cost while still maintaining accuracy?

I'm thinking this over as I type and the programming part would not be needed as the servos would be connected by wire to power the joint and all I really need is an on/off function and pulling the plug would serve the purpose I need.

If this isn't clear please inform me. I find that when I type on forums my vocabulary leaves me. Perhaps it's some form of stage fright. I don't know.
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So that several joints could be hooked up to one servo,
You don't seem to understand that the servo is doing, apparently. No, you can't have one servo for multiple joints.

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I would use a LilyPad Arduino USB as this particular Arduino would fit in your palm
Why does that matter? It's the servos that take up a lot of space, along with the joints. Minimizing the size of the Arduino is not really a factor. If it were, the Micro would be a better choice.
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You seem to be focusing on disabling servos (or joints) rather than making them work. It seems to me that making them work is the problem. I can't imagine why you would want to stop it working, but if so just disconnect/switch off/disable whatever part you want to stop working.

To make it work you need to have a signal generator capable of controlling the position of as many servos as you need in your solution. Arduino could be that signal generator if you like. You would need some controller to define the movements that you wanted to achieve i.e. how the servo positions change over time. There are lots of different ways to achieve that, some that can be done on the Arduino. Have you decided what you want the robotic hand to do?
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Poole, Dorset, UK
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Assuming that you are trying to make a basic working model of a human hand then a look at the anatomy of the hand makes a good start. Try this link http://www.livestrong.com/article/207815-tendons-in-the-human-hand/.

If you think about it you only need one servo (of the standard type) per finger. But the thumb now that is something else.

Mark
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Chicago
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You seem to be focusing on disabling servos (or joints) rather than making them work. It seems to me that making them work is the problem. I can't imagine why you would want to stop it working, but if so just disconnect/switch off/disable whatever part you want to stop working.

To make it work you need to have a signal generator capable of controlling the position of as many servos as you need in your solution. Arduino could be that signal generator if you like. You would need some controller to define the movements that you wanted to achieve i.e. how the servo positions change over time. There are lots of different ways to achieve that, some that can be done on the Arduino. Have you decided what you want the robotic hand to do?
I'm focused on disabling joints, because I want to see if less joints are activated (if we had less joints in our fingers) how much movement would be restrained. Getting it to work will be a challenge. I just want the fingers to move on the hand, the wrist and other parts don't matter as that's not what I'm testing.
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Check youtube for ideas like below.


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I just want the fingers to move on the hand

How do you want them to move? In other words, what is going to define the movement? Are you going to have a huge bank of potentiometers (connected to what)? A sensor glove so that it mimics a real hand? A hard-coded sequence of movements? Something else?
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Chicago
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I just want the fingers to move on the hand

How do you want them to move? In other words, what is going to define the movement? Are you going to have a huge bank of potentiometers (connected to what)? A sensor glove so that it mimics a real hand? A hard-coded sequence of movements? Something else?
It would be a hard coded series of movements (just the finger moving up and down) and I would how the angle at which it could move was affected by the amount of joints turned on.
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Good - that eliminates a lot of potential complexity to provide input devices and controllers.
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Good - that eliminates a lot of potential complexity to provide input devices and controllers.
I think it would be cool to make a prostheses based on an Arduino but I don't have the experience, time, or money to do that.
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the amount that your fingers can flex naturally without force against them is 180 degrees

This seems like a bogus claim.  I have no trouble curling up my fingers so that the last segment has rotated 270 degrees from the flat palm initial configuration.
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