Several of the 'Environmental Test Chambers' which I have come across during the 'Stress Screening' of electronic subsystems were fitted with 'Circular Chart Recorders' which recorded process parameters such as temperature, humidity and pressure-altitude on a circular chart as a real time record of the overall test plan.
Recently my computer Hard Disk failed and I opened it up with a view to see if something could be made out of the basic parts.
The similarity of construction between this HDD and a circular chart recorder immediately struck me:
Keeping this in mind I set about trying to modify the HDD to a circular chart recorder.
In the steps ahead I will bring out:
Finally I realized that although the concept is good, several practical problems came in the way of attaining a working system. I document these findings and suggest possible ways ahead.
I would appreciate any feedback to get this project working!
I disassembled the spindle motor and examined its mechanical and electrical characteristics.
I used a small compass to mark out the N/S poles of the annular magnet within the spindle. I found 4 pole pairs.
The spindle motor is basically a brush-less motor and the winding is arranged as a 'Y' with 3.3 Ohms between terminals.
When used as a stepper I found that there are 6 X 4 = 24 steps possible. However because of the 'Y' configuration and the center-tap not being brought out micro-stepping would not be possible.
It is therefore not possible to use this motor for the chart drive as the rotation resolution would be very poor.