Electronics > Beginners
Mysterious component found on most HDD PCBs
tchicago:
Hi, All,
I'm curious what is that rectangular glassy whitish component that most of the HDD PCBs have? Attached is a compilation of the various HDD PCBs with that component shown.
Some facts about it:
- It is positionally marked like MT1 or SK1
- It is definitely polar, sometimes the PCB has "+" next to positive terminal
- Sometimes there are several of them on one PCB
- It is usually installed at a strange angle to the PCB, if there are several of them then they can be at an angle to each other
- Sometimes each of them has a dedicated IC next to it. Especially noticeable if there are several of them on different corners of the PCB
- Sometimes this component has a guard trace around it, like protecting a high impedance component from the noise.
Is it a vibration or acceleration sensor? Or a shock sensor that voids the warranty?
LateLesley:
I did a bit of googling, and it does seem that they may be some type of piezoelectric shock sensor. Here's an example datasheet.
http://www1.futureelectronics.com/doc/MURATA/PKGS-00LD-R.pdf
Jwillis:
They're to detect sudden changes in acceleration ,rotation or impact. The signal from the sensor tells the hard drive to park the head in an instant to prevent the heads from crashing (Head Crash)onto the platter preventing permanent damage to the head and /or magnetic media on the platter surface.
tchicago:
Thanks! Really interesting. I guess my next step would be to take some unneeded HDD apart and see how this feature works and how effective it is. Maybe Dave would have made an interesting educational video out of this :)
JustMeHere:
Free fall sensors have been there for years and have been used to protect the HDD manufacturers from bogus drop claims.
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