Monday, October 25, 2010

DIY hard drive clock (part 6)

Illuminated push buttons.

Here's another simple micro DIY tutorial: LED and tactile switches are combined into illuminated push button.

Buttons are mounted on a small home-made PCB.
Two buttons electrically connected in parallel and resemble momentary switch.
LED is sitting on top of buttons and transmits force to switches when pressed.
Spring shaped leads are soldered to the board.
LED motion is relatively short so it shouldn't affect integrity of electrical connection.

Buttons and LEDs are connected to digital port of microcontroller and can be controlled independently.

Monday, October 11, 2010

DIY hard drive clock (part 5)

PIC18F2320 based controller for hard drive clock.

Hard drive clock is powered by Microchip PIC18F2320 clocked at 40MHz.
PIC18F2320 is a fast and versatile microcontroller with hardware I2C serial interface and plenty of I/O ports to handle communication with all external modules.

Actually, any medium range microcontroller can be adapted for this project. I have quite a collection of various PIC microcontrollers and I've chosen chip with excess of memory and I/O ports to allow some modification in the future.      

PIC18F2320 based clock controller.

Sunday, October 10, 2010

DIY hard drive clock (part 4)

Real time clock DS1307.

Excellent compact SMT design intended for embedded applications, made by Sparkfun.
This tiny assembly contains I2C compatible RTC chip DS1307, clock crystal, back up lithium coin cell  (CR1225 41mAh) battery and 5-pin connector.

I2C interface allows easy integration into any microcontroller based design.

Fresh battery should provide enough energy to support time keeping capability for very long time without external 5V power. According to Sparkfun, up to 9 years.
Well, I cannot wait such a long term to prove it so I take it as is;-) 

Real time clock DS1307.

(part 3)<--- DIY hard drive clock ---> (part 5)

DIY hard drive clock (part 3)

Index sensor

Purpose of  index sensor is to detect beginning of disk revolution to synchronize image being generated.
There are many kinds of remote sensors with identical logic output which are suitable for this task. The only difference between them is how sensors  interact with indexing disk.
- IR photo interrupters. Require cut slot or hole in disk.
- IR photoreflective sensors. Require high contrast mark (black line on a white background) placed on a disc surface.
- Hall effect sensor or reed switch. Require magnet attached to disk.

I've searched through my parts cabinet and found among my stock few SS49E analog Hall sensors.
Output  of SS49 is proportional to the strength of the magnetic field.
Normally  output is 2.5V but it rise up to 5V or drop to 0V when sensor is facing corresponding pole of a magnet.

Friday, October 8, 2010

DIY hard drive clock (part 2)

RGB LED light installation.

Any type of LED light can be employed for this clock design but since my discovery of affordable flexible RGB LED strip I use it in most of my LED based projects.
LED strip has self-adhesive backing and consists of easily separated sections and intended for 12V operation.
Every section contains 3 RGB LEDs with common anode, SMT current limiting resistors and soldering pads on each end.

Electrically all sections in the strip are connected in parallel so whole LED strip can be powered by connecting supply cable to any section. 

Flexible RGB LED strip and more rigid plastic base.

Tuesday, October 5, 2010

DIY hard drive clock (part 1)

Hard drive dissected.

Now it's time to take hard drive apart and see what we can reuse.
My victim is SCSI Fujitsu brand with spindle speed 4400 RPM. Full disk revolution takes 13.64 mSec.

Hard drive. Open and eager to get new guts. 

Some parts definitely can be reclaimed for other projects.
Voice coil actuator; can be used as laser beam shutter or as simple galvo. 
Couple very strong neodymium magnets; those may be used in solar pendulum  toy.
Hard drive platter itself is highly reflective and can be used as front surface mirrors for laser spirograph project.