| ??? 01/24/09 16:22 Read: times |
#161718 - Maybe it will work ... or maybe not. Responding to: ???'s previous message |
Chico Magalhães said:
Hello, I want to drive a voice coil from a HDD, I thought in installing a type of potentiometer in its shaft to receive the feedback, but I don't know now if its better to connect this potentiometer to an ADC and make the control via software by a H-bridge, or some type of circuit that receives digital or analog signal from the microcontroller then makes the comparison with the potentiometer by itself. The voice-coil driven hard disks with which I'm familiar drive the voice-coil "open-loop". By that, I mean they set the excursion of the head stack by driving a DAC. The loop, ultimately, is closed by the signal from the heads. The voice-coil driven (Persci) floppy disk drives I used back in the '70's were strictly open loop, since their track resolution was pretty coarse. Also, I thought about a led that moves with the coil, and a photo diode fixed to make the feedback, can this work? What information do you propose to gather from the LED+photo sensor combination, and how do you intend to interpret it? Is what I'm saying right?
What is better? In case of the circuit, what its name? I think you need to spend some time reading about feedback and servo circuitry. Thanks. Good luck! RE |
| Topic | Author | Date |
| Closed loop for HDD head coil help | 01/01/70 00:00 | |
| Maybe it will work ... or maybe not. | 01/01/70 00:00 | |
| Gradient transparency + led + photo-diode? | 01/01/70 00:00 | |
| it will not be easy | 01/01/70 00:00 | |
| more info | 01/01/70 00:00 | |
| It's not as easy as one might think | 01/01/70 00:00 | |
| harder than I thought | 01/01/70 00:00 | |
| There are ways ... | 01/01/70 00:00 | |
| speed is essential when drawing | 01/01/70 00:00 | |
| Yes, faster is better in this case | 01/01/70 00:00 | |
| Relativity | 01/01/70 00:00 | |
| That would likely work | 01/01/70 00:00 | |
Flexible Thinking - Flexible Arm | 01/01/70 00:00 |