CD Tray like circuit

[Sanghera]

Hi,
Not sure if this is the right place to post this but.
Just wondering what kind of circuit is used to op/close cd trays on desktops. You push the button it opens and stops the motor at the end and then you push the same button and it closes and stops the motor at the limit. You can also switch direction pushing the same button again in the middle. Or even more complicated one of those car flip up screens where they come out stop, flip up stop move in a bit and stop. Then you can do the same thing in reverse.
Thanks.

[smarbaga]

mostly a mechanical cct , with opto's at the limits , or the mirro times the motor, with motor current scenseing.

[Sanghera]

What is mechanical cct? By current sensing, do you mean a pot connected to the device changing the current?
Thanks.

[smarbaga]

hello:
mechanical circuit, anything mechanical be it gear racks, coggs , worms, cams, leavwes, followers, etc. as to the current , it is more likely timming, opto detectors and voltage regulation, just a guess tho.

[abasir]

Most CD player has microcontroller of some sort (to read data, error correction, spindle speed control, etc). A switch is connected to the uC IO port. Once press, the uC will enable the H-bridge to switch the DC motor for the tray until a limit occur (either opto or current sense). If switch is press while tray in motion, the uC just reverse the current flow to the DC motor.

[Sanghera]

What kind of microcontroller would this be and what kind of H-bridge?
Thanks.

[smarbaga]

there are only a handfull of cd core manufacturers
the same as with laser print engines
the make there own chips and propriotary circuits

[Sanghera]

I was just wondering about the basis of these circuits to run these types of things. What it takes to get something to move in that way.
Thanks.

[j m]

hi Sanghera,
Are you trying to make one?

one of those car flip up screens where they come out stop, flip up stop move in a bit and stop.

I don’t know if this helps but on tv [pimp my ride] program they mounted a small tv screen in the back of a car seat and used a automatic aerial from a car to move it up and down.
Or if you wand some thing to go backward and forward you could use a 555 timer as a Bistable (flip-flop) - a memory circuit with a SPDT relay and read switches. I have done this for my brother’s model railway to get a train to travel a long a strait peace of track and the change direction when it get to the end, this I quite ease to do.
jm

[Sanghera]

Could you go into a bit further depth with that? Is there anyway to use an H-bridge with a single push button?
Thanks.

[j m]

Do you mean me?
With the aerial I think it was all inbuilt in the unit and they just connected a switch were the radio would be connected, but I don’t know.
And the 555 just sends it continually back and forth.
This mite help http://www.robotroom.com/HBridge.html
jm

[gar]

050903-1854 EST USA

Sanghera:

First, you need to define the logic of the circuit. This may need to be done interactively with your choice of components.

You need to define what the push button action is be at different points, what the position sensor will be, whether mechanical stops exist at each end, what to do when you get close to an end, what happens when the motor is overloaded ( you grab and stop the motion ), and is motor overload funtion the same at the ends as in the middle.

Suppose you make these assumptions ---
Limit switches exist at each end of travel, and they actuate 0.05" from the mechanical stop.
Mechanical stops also exist at each end.
The drive system has one overload level.
When overloaded the motor stops where it is, and does not restart when the overload is removed.
When a limit switch is in an asserted condition, then the pushbutton must be held until the assertion is lost.
If the motor stops for any reason, then the next operation of the pushbutton sends the motor in the opposite direction.
After a limit switch is asserted, then the motor runs until overloaded (meaning against the mechanical stop).

Maybe more information is needed, but with these assumptions or your own you can then at least start the design of a combinatorial logic circuit, or a microprocessor program.

Then you experiment with the system looking for bugs and figure out ways to solve them.

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