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need help with HDDJ Turning an old hard disk drive into a rotary

I'm new to instructables.com and found a very interesting guide.
https://www.instructables.com/id/HDDJ_Turning_an_old_hard_disk_drive_into_a_rotary/?ALLSTEPS
but I'm not a electric technican, and don't understand all steps.
I understood how to open the HDDJ and i can sold the wires correctly. i know that the motor is used as a dynamo, so that I can measure the energie produced.
My first question is why are there 4 soldingpoints? - Are there 4 magnets which produce the energie, and every magnet has a soldingpoint.
I got a problem with "amplifying the output"
"One of the lines from the HDD is used as a reference, and is connected to the (-) inputs of all the comparators. The other three lines are connected to each of comparators (+) inputs. Not shown in the schematic, but also important, are the power supply pins of the comparators. The negative supply is connected to ground, while the positive supply is connected to Vcc (in our case +5V)."
Which wire I have to use as the reference? Maybe why?
What is Vcc? an energie source, like a batterie?
If I amplified the output which microcontroller I could use, can I use any mikrochip, or do I have to use a special?
and how do I install the firmware?

Maybe someone could help me with my questions. Maybe someone who is able to speak german so it would be a lot easier for me.

regards
Murphys Law

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Murphys Law (author) 8 years ago
thank you 11010010110 nice explanation. How can I see which coil is the - of all coils? "Not shown in the schematic, but also important, are the power supply pins of the comparators. The negative supply is connected to ground, while the positive supply is connected to Vcc (in our case +5V)." What should i do exactly? What is the Vcc here exactly? Should I use a battery, or is there something in the HDDJ? Which microchip can I use?
in some drives (hitachi) you can see wires coming rom the motor. D has 3 wires connected together if no then measure resistance. itll be lower if one of the points is D and higher otherwise you take vcc from the main 5 V supply of the project. it may be USB or 7805 etc common comparator chips are LM324 (4 in a chip) and LM358 (2 in a chip). there is LM741 (1 in a chip) but on my limited experience its not very reliable
Murphys Law (author)  110100101108 years ago
how do I connect - to ground? The 7805 is a microchip and got a ground output too? Which microcontrollers could I use?Which requirements does the microcontroller have? Could use these: PIC12F629-I/P EEPROM 93LC66B/SN (MICROCHIP)
7805 has 3 entries the center goes to earth. it is the common - of both the 5 V out and the higher voltage in the right (if you hold it with the text in front of you and the hole up) is the + of the 5 V out (the vcc) the left is the + of the in i guess you can use any controller (maybe with some modifications to the software). at most you can make part of it in software on the actual computer instead of the controller (and simplify the controller tasks) i think you might hack in a circuit from old mouse (with ball) instead of the controller. the spinning of drive simulates moving it right left / up down / scrolling the wheel (you choose)
Murphys Law (author)  110100101108 years ago
I have to sold the 3 coils with the 1kOhm resistor and than with the +input of the LM324D and the 4th coil with each - input and no resistors. Than I have to sold the 3 outputs of the LM324D with the 10kOhm resistor to the input of themselves and without a resistor to the input of the microchip.Than I have to sold a USB-wire to the USB-output of the microchip. I have to sold the - output of the microchip to the - input of the LM324D and the +output of the microchip to the +input of the LMD324D. (the out- and inputs for the energie and not the signal). Than I have to connect the microchip per USB to my PC and install the firmware. How do I install it? Was that right to this point? What do I have to do than?
you connect the components as in that drawing. all chips etc get vcc (+5 V) from the red wire in the usb and earth (-) from the back wire in the usb it surprises me that it does not matter what connection is D. i'd still try to identify it and use it for earth and ABC for the 324 inputs after connecting it you use some software to upload the firmware to the chip my knowledge ends at the micro controller. from here on you better ask some1 else like the maker of the instructable (in the inst comments)
110100101108 years ago
in most hard drives there are 3 coils in a setup known as star setup think of it as world directions coil A is with + on east and - on west coil B is with - on north north east and + on south south west coil C is with + on north north west and - on south south east the + go to 3 points A B C respectively. the - of all coils go to point D. here are the 4 entries of the motor you see. in some drives its visible which one is D now imagine a red dot on the disk surface when you apply positive voltage to coil A (connect a battery with + to A and - to D) the plate moves so that the dot is near the + (east) when you apply negative voltage to coil A (connect a battery with - to A and + to D) the plate moves so that the dot is near the + (west) most drives dont use negative voltage. the point D is constantly connected to - and the circuit gives + to points ABCABC in this order. this makes the drive spin. the motor can handle negative voltage though. ths capability is just unused when you spin it the voltage you get on each coil is positive when the dot passes over the + end of the coil in the forward direction if you spin the plate forward you get the max positive voltage on A when the dot passes the east. it fades to 0 as the dot gets close to north. then it rises and gets the max negative voltage when it passes over the west. then it fades again to 0 on south. you know how it continues if you spin it back you get + at west and - at east each coil makes the voltage depending on the position of the dot relative to it. you have 3 coils so they make voltages ABCABC or ACBACB depending on the direction you spin it. the voltage and speed of the sequence depend on the speed at which you spin
Sandisk1duo8 years ago
vcc = positive input voltage

why 4 soldering points? -> the motor inside the hdd is a stepper motor