Notes on life, art, photography and technology, by a Danish dropout bohemian.
When you drink the water, remember the river.
Monday, June 29, 2009
Wood iPod
This is cool. If somebody did this for money and with present models, I would be game. (An iPod Mini. Man, that's a while ago, innit? I'd almost forgotten those. It's one of the few I never had.)
Hey Alex and Eolake, hopefully i can explain how the new click wheel works for ya!
when i first took apart the mini,i didn't realise that the original ipod's white click wheel (the one with the play, menu and fwd markings) is actually simply a plastic cover around 1mm thick that sits above the click wheel sensor.
That made me realise that the sensor MIGHT not even realise if i swapped that plastic cover with a wooden one. (i reckon wood is just about as non-conductive as plastic is?) so! there was hope for me that i could try and make a really thin wood replacement.
The wooden clickwheel isn't veneer, rather I shaved it down from a block of wood to end up with a 2mm thick piece and I was happily surprised when I placed the wood wheel on the sensor and it picked up my finger just fine. The whole capacaitive process works great with the new click wheel cover. I guess it's the same principle as how you can often operate your ipod through a layer of denim while the ipod is in your jeans pocket?
hope that explains it for you guys, thanks for the post of my ipod too Eolake!
I really like case mods, and this one is pretty elegant.
Can you believe I've seen iPods at a distance, but I don't remember playing with one. I was thinking the wheel was more like a touchpad on a laptop, not a wheel above a sensor.
I really should play around more with this sort of thing. I need practice in the workshop.
"How does the ipod static wheel sense your finger?"
I've never taken an iPod apart, so I'll have to feed you a generic answer, consider yourself warned! (and do pass the warning along if you post this) ;-)
"Is it the electric field from your body?"
No, not really. Your body does not have an intrinsic electric field to start with. But it is a conductor, and has quite a large surface. Being constantly bombarded by radio waves of all kinds and origins (basically everything you can tune in using radio gear (or TV, obviously), plus interference (noise) generated by most electrical equipment, etc.), your body can act as a pretty decent antenna.
A basic capacitive detector, like the on/off switch in a touch lamp, is very simply an amplifier trying to detect radio frequency (RF) energy, but without an antenna connected to its input. When you touch the amplifier's input circuit, your body acts as the missing antenna and supplies plenty of signal to be amplified. The sudden surge at the output of the amplifier is detected and that's what causes the lamp's state to toggle.
Why does this work across an insulator, like the plastic wheel on the iPod? There are many ways to explain this, but a simple analogy might be best if we want to avoid techno babble and keep things simple. You can compare radio waves to sound waves for this purpose: they both propagate in the distance, can travel through more-or-less dense obstacles or even find their way around "solid" obstacles (via echoes, etc.). In the case of the iPod's plastic wheel, it's like a paper screen for sound, i.e. it's pretty much non-existent for practical purposes.
Finally, the way to detect the position (and thus the motion) of your finger on the wheel of the iPod is simply to use multiple detector inputs. I'm guessing here (see above warning), but I would say that two progressively overlapping inputs would be enough. To picture this, draw a rectangle 10mm high by 100mm wide and split it in two along a diagonal. Connect one of the resulting triangles to detector A, and the other to detector B. Depending on where you place your finger along the rectangle, each detector will receive a signal intensity proportional to the respective area under your finger; it is thus possible to determine the position of your finger by observing the ratio of input signals. Wrap this in the shape of a donut, and you have an iPod wheel detector. The actual implementation will probably differ, but the idea remains.
we're not just photographers out here (or voyeurs), we can cope with some electronics :-)
One of our products uses RF capacitive switches for user input, we've got board trace antennae, an air gap, then etched Plexiglas panel. The RF one is not the mystery. I was thinking of the later iPods which seemed to only respond like my touch pad PC. I thought these relied on physical contact. Seems the original click wheel was just that, a wheel.
Anyway, thanks for the fresh interpretation, embedded.com sometimes gets a bit wordy.
I knew you wouldn't have a problem, and actually expected you to chime in earlier since you were part of the discussion from the start. The reason why I didn't put my 2 cents in, before being asked that is, is because I don't use iPods, and have never dismantled one. I am therefore relegated to guessing here.
The earliest implementation of a stationary scroll wheel that I can recall used rudimentary strain gauges to detect motion. I unfortunately forgot what it was used on... it's been over twenty years since then!
The reason why I suspect a true capacitive sensor using RF noise as the trigger is for both compactness and low-power operation, two critical parameters for a portable device like the iPod. And the latest versions certainly have no room for switches!
But hey, if anyone knows more about the actual construction of those devices, feel free to correct me.
Trouble is, that was a design before I joined the company, and I've sinced reviewed schematics for projects where I would have been talking touchless buttons, but they were shelved.
I'm on the edge where I only have to understand the concept, as we found a chip that would give a true/false level after doing the math on the RF.
As for EO buying things, are you interested in light sculptures and interesting ambient lighting?
Funny thing, BTW, the iPod Nano's scroll wheel is far more sensitive than the iPod Classics. The latter can actually be a little irritating, because you never know when it'll start reacting.
And that fancy keyboard of yours, I believe, turns up in the new TV show "Warehouse 13". Check with whatsisbucket who made it, he may be famous now ;-)
13 comments:
Hmm, does the wood veneer on the touch wheel impact the performance of the dial . I've heard it's RF capacitive...
I was wondering about that.
I don't understand how that touch wheel works.
Hey Alex and Eolake,
hopefully i can explain how the new click wheel works for ya!
when i first took apart the mini,i didn't realise that the original ipod's white click wheel (the one with the play, menu and fwd markings) is actually simply a plastic cover around 1mm thick that sits above the click wheel sensor.
That made me realise that the sensor MIGHT not even realise if i swapped that plastic cover with a wooden one. (i reckon wood is just about as non-conductive as plastic is?) so! there was hope for me that i could try and make a really thin wood replacement.
The wooden clickwheel isn't veneer, rather I shaved it down from a block of wood to end up with a 2mm thick piece and I was happily surprised when I placed the wood wheel on the sensor and it picked up my finger just fine. The whole capacaitive process works great with the new click wheel cover. I guess it's the same principle as how you can often operate your ipod through a layer of denim while the ipod is in your jeans pocket?
hope that explains it for you guys,
thanks for the post of my ipod too Eolake!
Josh d
Josh,
I really like case mods, and this one is pretty elegant.
Can you believe I've seen iPods at a distance, but I don't remember playing with one. I was thinking the wheel was more like a touchpad on a laptop, not a wheel above a sensor.
I really should play around more with this sort of thing. I need practice in the workshop.
Cheers
Alex
Alex, the first gen iPod had an actual wheel. The later ones has a static plate, it does not turn.
Josh, could you mod an iPod classic for me? I'll pay well.
See another mod I've bought, here.
I asked Bert, he said:
"How does the ipod static wheel sense your finger?"
I've never taken an iPod apart, so I'll have to feed you a generic answer, consider yourself warned! (and do pass the warning along if you post this) ;-)
"Is it the electric field from your body?"
No, not really. Your body does not have an intrinsic electric field to start with. But it is a conductor, and has quite a large surface. Being constantly bombarded by radio waves of all kinds and origins (basically everything you can tune in using radio gear (or TV, obviously), plus interference (noise) generated by most electrical equipment, etc.), your body can act as a pretty decent antenna.
A basic capacitive detector, like the on/off switch in a touch lamp, is very simply an amplifier trying to detect radio frequency (RF) energy, but without an antenna connected to its input. When you touch the amplifier's input circuit, your body acts as the missing antenna and supplies plenty of signal to be amplified. The sudden surge at the output of the amplifier is detected and that's what causes the lamp's state to toggle.
Why does this work across an insulator, like the plastic wheel on the iPod? There are many ways to explain this, but a simple analogy might be best if we want to avoid techno babble and keep things simple. You can compare radio waves to sound waves for this purpose: they both propagate in the distance, can travel through more-or-less dense obstacles or even find their way around "solid" obstacles (via echoes, etc.). In the case of the iPod's plastic wheel, it's like a paper screen for sound, i.e. it's pretty much non-existent for practical purposes.
Finally, the way to detect the position (and thus the motion) of your finger on the wheel of the iPod is simply to use multiple detector inputs. I'm guessing here (see above warning), but I would say that two progressively overlapping inputs would be enough. To picture this, draw a rectangle 10mm high by 100mm wide and split it in two along a diagonal. Connect one of the resulting triangles to detector A, and the other to detector B. Depending on where you place your finger along the rectangle, each detector will receive a signal intensity proportional to the respective area under your finger; it is thus possible to determine the position of your finger by observing the ratio of input signals. Wrap this in the shape of a donut, and you have an iPod wheel detector. The actual implementation will probably differ, but the idea remains.
Bert,
we're not just photographers out here (or voyeurs), we can cope with some electronics :-)
One of our products uses RF capacitive switches for user input, we've got board trace antennae, an air gap, then etched Plexiglas panel. The RF one is not the mystery. I was thinking of the later iPods which seemed to only respond like my touch pad PC. I thought these relied on physical contact. Seems the original click wheel was just that, a wheel.
Anyway, thanks for the fresh interpretation, embedded.com sometimes gets a bit wordy.
Alex
Alex,
I knew you wouldn't have a problem, and actually expected you to chime in earlier since you were part of the discussion from the start. The reason why I didn't put my 2 cents in, before being asked that is, is because I don't use iPods, and have never dismantled one. I am therefore relegated to guessing here.
The earliest implementation of a stationary scroll wheel that I can recall used rudimentary strain gauges to detect motion. I unfortunately forgot what it was used on... it's been over twenty years since then!
The reason why I suspect a true capacitive sensor using RF noise as the trigger is for both compactness and low-power operation, two critical parameters for a portable device like the iPod. And the latest versions certainly have no room for switches!
But hey, if anyone knows more about the actual construction of those devices, feel free to correct me.
Trouble is, that was a design before I joined the company, and I've sinced reviewed schematics for projects where I would have been talking touchless buttons, but they were shelved.
I'm on the edge where I only have to understand the concept, as we found a chip that would give a true/false level after doing the math on the RF.
As for EO buying things, are you interested in light sculptures and interesting ambient lighting?
Not for where I live now! No space.
Funny thing, BTW, the iPod Nano's scroll wheel is far more sensitive than the iPod Classics. The latter can actually be a little irritating, because you never know when it'll start reacting.
And that fancy keyboard of yours, I believe, turns up in the new TV show "Warehouse 13". Check with whatsisbucket who made it, he may be famous now ;-)
Datamancer's Aviator keyboard? Kool.
(See it here.)
http://www.datamancer.net/blog/?p=27
Wow, he did more than just the keyboard. What a cool gig.
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