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Poor Man's Digital Joystick

Which would actually cost more to home-brew than a cheap analog stick.
  [vote for,

Picture linked. I will try to post one of the guide frame later. I'd suggest you start there, as the description is a little muddled. I gave up on comp sci after a semester, as my math is less than exceptional.

A very simple x,y input needing only one single sided PCB, a stamped metal sheet for the contacts, and a plastic guide frame.

Basically, it is a bunch of switches that output a coordinate as a binary number, sending all the bits in parallel.

The PCB divided into blocks. Each block is broken into stripes. A contact (brush, metal dimple, ball bearing, etc.) moving along the stripes will have no effect on the state of the block. Moving across the stripes, the block switches on and off. Each block corresponds to a particular power of 2 for the x or y coordinate.

The frame is just a plastic bit which allows the PCB to slide along one axis, and the contact plate along the other. Although, in actuality the plastic frame would probably be sliding, and one of the other parts remain stationary.

It could happen in any way, depending on the installation. Since this would be clumsy for more than, say 4 bits/axis (maybe 8 of you made a sandwich of PCB-contacts-PCB) I imagine it being most useful for portable devices, printed on the same PCB as everything else. Most of these devices don't need a high resolution input, and don't have room for the usual arrangement of rotary encoders.

tiromancer, Dec 21 2004

(?) Picture http://tiromancer.e...n.com/joypad01.html
It's a picture [tiromancer, Dec 21 2004]


       Thanks. I'm interested in X Y coordinates being rotate. Computer science, how much longer do we need that?
mensmaximus, Dec 21 2004

       So what you're proposing is basically to use two four-bit linear encoders in place of two potentiometers, with the four-bit linear encoders' operation predicated upon keeping the orientation of an upper PC/contact board absolutely consistent with that of the bottom one as it's moved around?   

       Somewhat clever implementation, though I would expect that the mechanics required to keep the sliding board oriented correctly would probably be more expensive than those required to operate two pots.   

       Also, I would tend to think that it might be easier to use three stacked boards, arranged such that the middle one slides north and south on the bottom one, while the top one slides east and west on the middle one. Since the top and bottom 'boards' in this case could simply have one wide contact each, they wouldn't really have to be PCB's.   

       BTW, you should read about gray codes and why they're important for this sort of application.
supercat, Dec 21 2004

       Added sketch of the frame. I think it would be fairly simple, though I don't know that it would be cheaper than using pots.   

       The reason I started thinking about this was to eliminate the ADC. I don't know if that would really save any money, overall, but I decided it doesn't matter. This set up, at its simplest, requires only one PCB, which presumably is already available in most applications. And regardless of how you set it up, it will be thinner than a pot.   

       I considered a three layer set up similar to what you describe, with 8 bits per axis and joystick coming up through the center of the PCB. I felt that a thinner, simpler, and lower resolution device might be more useful though, and more importantly easier to draw.   

       Anyway, that's all assuming it would actually work, which I don't know. I wish I'd heard of Gray Codes before I started, it's pretty fantastic material. I really feel a lot less guilty about having signed up for the Halfbakery now.   

       So, in short, thanks!
tiromancer, Dec 22 2004

       I can certainly see that conventional rotary pots can be bulky and the digital method isn't bad. I suspect that since you'll probably have to have a nested slider arrangement to keep things straight you may as well put contacts on the nested sliders (so you have two one-dimensional encoders). Using a gray code may or may not be better than using analog inputs. I do know that I once implemented a 3x4 keypad using some resistors and ADC's (so the keypad could connect with four wires).
supercat, Dec 22 2004

       [tiro] - nice! I didn't really understand the plans, but the basic idea is plain enough and makes a lot of sense. Bunnage.
wagster, Dec 22 2004


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