3 ms·
Neat. And it's a curious feeling to stumble upon memories I haven't touched in years -- I used to love idly disassembling computer mice, cleaning out fuzz and
by jtheory 12y ago
Neat.
And it's a curious feeling to stumble upon memories I haven't touched in years -- I used to love idly disassembling computer mice, cleaning out fuzz and gunk from the little rollers and the ball, and putting them back together. It was one of things I had to consciously stop myself from doing if I was sitting at someone else's desk.
Optical mice have been around so long now, I had completely forgotten how they used to work, and that odd little pleasure of maintaining a simple mechanical device.
Edit: this confuses me, though: The basic approach — pairing a freely-rolling ball with a optoelectronic system — was used by generations of mice that followed, changing only incrementally until optical mice did away with trackballs altogether.
Is that right? The mice I was always taking apart normally detected the motion of the trackball with two little white rollers, for Y and X motion. That's neither of these systems.
- rjsw 12y agoIn all the mice that I have seen the position of the rollers is detected by an optoelectronic sensor on each of them.
- dammitcoetzee 12y agoYes, that's right. The little rollers were on an axle that extended a bit further terminating into a spoked disk which sat in the middle of an optical detector and emitter pair. It used some tricks to figure out when the mouse was going forward and when it was going backward (quadrature), but mostly it just counts the pulses of light it sees and turns that into displacement coordinates. EDIT: Wikipedia has a pretty good picture of this and a better explanation: http://en.wikipedia.org/wiki/Mouse_(computing)#Mechanical_mice http://en.wikipedia.org/wiki/Mouse_(computing)#Mechanical_mi...
- JoeAltmaier 12y agoI thought the holes in the disk were in Grey code? Maybe that reduces to quadrature in small cases
- joezydeco 12y agoThe encoder disc is really a 1-dimensional input. Adding a second opto-detector that is one half-bit out of phase gives you two simultaneous inputs and yes, it comes out to a 2-bit Grey code. 00 -> 01 -> 11 -> 10 -> 00
- dammitcoetzee 12y agoQuadrature is a gray code with two offset spoke sets so that you can tell direction and rotation by which pulse precedes the other. http://www.ni.com/white-paper/4763/en/ http://www.ni.com/white-paper/4763/en/