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The Secret Behind the iPod Scroll Wheel
Grump sent in a story saying "Ask any iPod user what they like the most about their device, and most will probably mention the scrollwheel. Here is the story behind the company that makes it (hint: it's not Apple). Great not just for the history, but insight as to both how Apple's design process works, and how the scroll wheel itself works."
This "article" just shows some pictures of what I can only assume is the touch sensitive plates under the wheels. It doesn't explain anything about them and how they work, nor does it really talk about the "design process."
but insight as to both how Apple's design process works, and how the scroll wheel itself works.
The article doesn't say how the scroll wheel works. It also doesn't mention anything about Apple's design process...
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The scroll wheel is just a round touchpad and is based on the same technology Synapsis has patents on. It even feels the same as the touchpad on my PowerBook.
I have a 4th gen iPod with the click wheel and after I finally figured out you just moved your finger to scroll (it wasn't immediately obvious and I've not had the opportunity to use previous versions) I've found it to be far more responsive than the touchpads I've encountered on notebooks. I have a Sony Vaio at work and I hate the touchpad on it, it's very difficult to control and way too sensitive registering double clicks even when my finger doesn't leave the surface. (Apparently pausing with your finger on the touchpad counts, I can't find a way to adjust the settings to fix it.)So I'd have to say that with the current generation clickwheels the touchpad on the iPod is far better. It's just sensitive enough without being too sensitive and it requires no adjustment to work that way. That alone is an achievement since there are so many different finger sizes out there and different people are going to push with different pressures.
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Touchpads are the best thing that ever happened to this company. They're getting licensing fees and royalties on almost every notebook sold, or they make money directly as the component vendor for the touch pads.
And deservedly so, they obviously can make some top notch ones (iPod clickwheel) so they're really earned those fees and royalties. At least they're not an IP company making money via lawsuit.The Pong system is a little different from the scroll wheel in that it senses the ABSOLUTE angle of a variable resistor whereas the scroll wheel detects RELATIVE angle of a rotary encoder. I know because I actually built a PONG system using GI's famous AY chip.
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Electronics Design Chain
Standard pulse timing is 10 pps, with a window from about 7.5-12 IIRC. It's been a while since I had to adjust the little mechanical governor that controlled the rotary dial return rate. Duty cycle is 50%. Pulse too slow and it will be mistaken for a hookflash. Too fast and you'll exceed the slew rate of the switch and drop pulses. Mechanical switches are, of course, more succeptible to too-fast pulse rates. Electronic switches can probably accept faster than 12 pps, but 10 is still the standard.
The "turning of the dial" creates no current. It interrupts the circuit. So does the hookswitch, which led to being able to "dial" a phone with the hookswitch. You still had to have good manual dexterity, especially when there were higher numbers in the number you were trying to reach. This was popular in the days when a coin telephone disabled only the dial circuit and not the voice path. Nowadays, of course, you can't do this because the dial tone you hear when you pick up is generated by the phone itself, which accepts your call information and then decides how to route the call.
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