CD ROM Read Head Actuator - Hacked Gadgets

[zolberserk]

do you know what the 17 pin connector RFO VR PD LD C B A E F VCC VC GND FCS TRK TRK+ FCS+

[idricool]

You morons the group and website is called hacked gadgets. Fucking retards. No one claimed the Cd rom "was hacked".

[canadiandude1919]

whats the model??

[flash11588]

yo some one would me the man if he can get a dvd laser the work in the dreamcast

[nrdesign1991]

There is a tiny push-switch that the head triggers when fully moved in (to the spindle motor). The position of the head is controlled by timing the power that goes to the motor. The actions the motor can do is stop (short wires), forwards (normal polarity) and backwards (reversed polarity). If the head loses track, the motor simply drives it back into the reset positikon. You can easily confuse a CD drive by pushing the button :-)

This assembly is cheaper to make, that's why it took over.

[Davidbzm01]

dude. thats not a hack. thats just a ripped apart cd rom. WTF

[ZXRulezzz]

DC motor that moves head assembly, and some circuitry that controls that motor, actually acts together as a servo.

Control circuit are designed to control not a movement, but motor's angle depending on a data that comes from the laser head itself.

[Gonamez]

???

[physicmad]

if you listen to a portable CD player, you can hear the motor pulse as it passes each block,

[physicmad]

now this side to side lense movement is what gives the minor track allignment. Since the motor has a absolute minimum movement the motor is only used ot move the laser lens to the next "block" or so. the lens control "stitches" these blocks together. making the data read seamless.

[physicmad]

When the laser is scaning you have two levels of track allignment - major and minor, the major track alignment is performed by the motor moving the head assembly. Now to keep the laser acurately set on the pit track, the lens head iself has an 2d plane movement. if you were to look at the lens focus coils, they are indipendently wired. If both are powered with the same voltage the head goes up and down. if one coil is powered and the other has the opposite polarity it moves side to side.

[albinocreampuff]

this isnt really a hacked gadget

[insanity54]

REVERSE THE POLARITY! That solves everything! (at least it does on star trek...)

[albinocreampuff]

lol

[K12Reversal]

The spindle is another story; they usually use a brushless motor and hall effect sensors because speed is critical here and it changes with the distance from center of the disc (constant tangential speed as opossed to constant angular speed in hard disc drives)

[K12Reversal]

If you make a close observation of the head while reading (specially a music disc, not a data disc), you will see the motor moving in "big" steps, and the rest of the position control resides in magnets and coils (the top lens of the head is "floating" suspended on thin spring wires usually).

[K12Reversal]

The motor moves the head just aproximately to the desired position based on CD reading info, and there is another mechanism (magnets and coils) to get the fine tuning of position and focusing the surface of the disc; this fine tuning must compensate the disc warp and excentricity all the time.

[amfan12]

This drive looks really low end. Most of the CD-ROM drives I've seen, if they use a regular DC motor for the head positioning, they have a little magnet ring and a few hall effect sensors on it to detect location

Most other drives I've seen also use brushless encoded motors for the CD spindle

[fizxgod]

it is possible to do have a closed loop controller using back-emf as a proxy for speed, but I doubt that's used here.

[fizxgod]

how many leads are coming off the motor area? if more than 2, there's probably an encoder.

if just 2 wires, it's probably just a simple open loop control system. (i.e. on/go-off/stop)

[abbtech]

You can see the pictures here. There is just two wires on the motor. I am wondering if it is looking at the CD information for position and shorting the motor windings when it is in position to quickly stop the travel.