Half a croissant, on a plate, with a sign in front of it saying '50c'
h a l f b a k e r y
Almost as great as sliced bread.

idea: add, search, annotate, link, view, overview, recent, by name, random

meta: news, help, about, links, report a problem

account: browse anonymously, or get an account and write.



CD adapter

Use your analog device on your CD player
  [vote for,

We have all seen the cassette adapter - the thing that lets you listen to your MP3 player/portable CD player/etc in your car. This is kind of the opposite of that. This two part device has a special CD that is read like a normal CD in your cd player with a transmitter that plugs into what you want to listen to.

Part one - Special CD. CDs work be either reflecting the laser back to a sensor or blocking the laser. There are read as ones or zeros to the player. This special CD would have a single endless track with a very fast LCD between it and the laser. The LCD would flash dark to block the laser or open clear to allow reflection. Since it has to be CD shaped, it cannot have cables. Etched on the cd (like a chip) would be miniature power generators, a receiving circuit and the LCD driver. New plastic technology makes the LCD possible and MEMS makes the generator possible.

Part 2 - transmitter The transmitter converts the analog signal from your device into a clean digital signal that the CD hears. It requires external power of some kind (battery, car adapter, etc). The transmitter plugs into your device to be cd enabled like headphones - just like the current cassette adapters. The transmitter would most likely use spread spectrum technology on some ISM band (900mhz, 2.4GHz, 5GHz, etc) for the wireless link to the CD.

gohlhausen, Apr 14 2002


       Might be cheaper to just buy a Walkman.
phoenix, Apr 15 2002

       This could be baked by providing a system which makes the CD drive believe that (1) a disk is in the drive and (2) there is data coming off it.   

       An IR led or laser driven with an appropriate signal could provide the second.
neelandan, Apr 15 2002

       You could move to the next track to switch to a different station...
(Disclaimer: None of this makes any sense to me at all.)
jutta, Apr 15 2002

       What's the output of a CD-ROM laser?
(Quick Google search reveals: "Laser power can range between 3.6 and 8.8 milliwatts. Laser wavelength can vary between 775 and 795 nanometers." - courtesy of the folks at Roxio) Mind you 8.8mW is about maximum power for a *CD-R* drive, not a *CD-ROM* drive. Nevertheless, I was able to turn up low-power FM trans!ceivers! that will run off about 1mW. Not knowing how efficient the conversion from laser light to electricity would be (but being an optimist) we might have some juice left over to run other circuitry.

       The wonderful irony is that this (were it feasible) would allow us to listen to our CDs on a radio and our radio on a CD player. Man, I love this place.
phoenix, Apr 16 2002

       I'm not sure I see how the CD would need to generate a laser, rather it has to provide a varying amount of reflection to simulate the patterns on a standard CD. The way I understood the concept, you'd start with a CD which is completely covered with a mirrored surface. Then, you put an LCD layer across the whole CD. This LCD layer is not pixels like an LCD display (you'd never have enough pixels to do anything useful relative to CD capacity), but instead just a single LCD element that can be changed from clear to cloudy. Since the entire surface is then switched from mirror to not-mirror, you don't have to worry about where the laser read lens is at any point, and you just have to have clever controls of the LCD on/off that simulate a standard CD bit timing.   

       Regardless, it sounds like an overly complex way to get an audio input to the speaker amplifiers...
spartanica, Apr 16 2002

       LCD technology is not going to provide the magic you were hoping for, [gohlhausen]. It is a fairly slow (relative to CD bit rates) mechanical process which changes a pixel from clear to cloudy and back. Also, you can't have just one huge super-pixel because it has to be able to twist 90 degrees around an axis parallel to the incoming light.   

       If you are going to muck with a radio transceiver in the anyway, just buy a low-power FM transmitter and wire the line-in to the headphones-out of the portable cassette player. Then pick up the transmission on your car's radio tuner. Done. The transmitter is available off-the-shelf, and (at least in the USA) requires no special licensing because the broadcast range is less than 50 feet.   

       // Regardless, it sounds like an overly complex way to get an audio input to the speaker amplifiers... //
I agree. Never buy a car audio system that doesn't have line-in connections available.
BigBrother, Apr 16 2002

       your idea is just useless. why you want to do something like that?
jedy, Apr 17 2002

       for something like that..i'd just buy a car cassette player for au$25, hook it up and use a adaptor for that....   

       not that i listen to anything but CD's anyway.....
Apathy, May 20 2002

       Something to consider.. You would not need to deal with the entire surface. Just as a cassette adapter only deals with the head directly, the laser only reads a small portion at one time. If the central ring was attached to the rest of the disc on bearings so just that part spun, then only the portion of the disc being read would need to be dealt with. It is still not standard to put line in connections on stock radios and I don;t want to buy a new radio just for that.
chaumai2, Feb 28 2003

       //your idea is just useless. why you want to do something like that//   

       (Triumphant Music) DA-DI-DI-DAHHHHH! Sounds like a job for the Halfbakery!
Cedar Park, Mar 01 2003

       Or you could buy a stereo with analog input jacks. You may even have them already on the back of your stereo. Just run a cable to the console.
tooluser, Mar 16 2003

       this is the way I see a cd adaptor-   

       a key shaped item that would set on the cd-drive motor and then latch onto the laser assembly. (you would need to sense the speed or the rotor, as well as provide the modulated laser light).   

       the laser of the input device would simply be modulated to whatever the cd player needs to see (be it the best two of three, or whatever)   

       and since the "key" assembly would not be spinning, you dont need any transmitters to give the device the datastream.   

       the inherent problem with this is, however, that most cd players probably read cd's differently. maybee sony uses a "best 12 out of 30 passes" and aiwa uses the standard "best 2 out of 3 passes."   

       The soloution to this problem would be, of course, to have each manufacturer produce their own "cd modulator" for input to a cd player.   

       Yet another problem, however, is that with car-sterios you would not be able to use the device at all (except for the drawer-loading sony in-dash video screen). The reason being, how would you get the head of the "key" onto the motor, AND get the shaft onto the laser assembly, without getting all tangled up in the cord?
robacarp, Jun 07 2003

       Marx was right. wait, no he wasnt.
kissing bandit, Sep 18 2003

       Oh good, somebody's already posted this idea, so I don't have to. It would be a lot easier to miniaturize the electronics now. Bluetooth with a PCB antenna, PCB generator, EDLCs for power buffering, etc.   

       I was thinking earlier, because LCDs are obviously too slow, that you could do this with a grating light valve. I calculated from the numbers given by Wikipedia that you need to be able to modulate the reflection at up to ~1.7 MHz (or higher because that's the square wave frequency, and the drive might not like a sine wave at that frequency), and a GLV should be able to do that easily. The only trouble is that current GLV devices seem to be thicker than 1 mm (the thickness of a CD) and maybe not long enough (though maybe you could convince the drive that the disc's track is circular rather than spiraling, and not need length?), but, if you got them custom-manufactured, that could be solved. Perhaps an electro-optic modulator could be used instead, but I've never seen one miniaturized anywhere near as small as even current GLVs. You could of course use your own modulable light source rather than a modulable reflector—I haven't calculated the power requirements for that (or for the reflection modulation approach, for that matter).   

       I was also thinking that it could have some sort of brake around the edge, to hold most of the disc stationary (with the modulable reflector or light source aligned with the drive's head track—it would have to allow itself to spin until it found the head) while the center is turned by the drive's motor and used to generate power, but it would be hard to design a brake that would work with all types of drive.
notexactly, Oct 03 2019


back: main index

business  computer  culture  fashion  food  halfbakery  home  other  product  public  science  sport  vehicle