SATA activity LED for each HDD

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Ckuke

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Jul 16, 2012
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Hello,
Situation:
1) want LED activity indicator for each SATA HD
2) have multiple SATA HDs, different models and capacities
3) No activity LED driver on controller or MOB
4) SATA power pin 11 function not consistent across drives (also a bit risky)

Question: Other than pin 11 schemes, is there anything available to provide activity LED for each SATA HDD?
 
Solution
F
Sorry, I should not have used an ambiguous acronym. By "VCM", I meant Voice Coil Motor.

As for common mode voltages, perhaps that would be one downside of a Hall effect sensor.

Should you wish, for testing purposes, to correlate voice coil and spindle motor current against the power supply current variations recorded by your circuit, then there are usually test points on the PCB that you could use for this purpose.

The motor current could be measured by monitoring a current sensing resistor, or parallel resistor array. One end of this resistor will be grounded. Similarly, you could sense the VCM current by monitoring a sense resistor in the VCM H-bridge. This resistor will be floating.

You can see these arrangements by referring to...
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Yes, I agree. In the old days one could hear all that, but not now, especially when you're hard of hearing.

Ckuke
 
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Heh, I no longer have my youth, but I still have my hearing. 🙂

BTW, I would think that 50kHz would probably be more than enough bandwidth for the mechanical parts of the circuit.

If you are interested in exploring HDD circuitry, I would suggest that you procure an older Maxtor drive (pre Seagate acquisition). Those old PCBs had all the test points clearly labelled. I would do this myself except that I no longer have your kind of motivation. :-(
 
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You're 50% better off than I - I've lost both.

Yes, I know what you're talking about. I have a bunch of old drives and possibly an old, old Maxtor. I'll have to do that. I know the theory but never probed one. You sound as if this stuff is your thing. I cut my teeth on a DEC PBP-8I. We had woven toroid mag. storage then, real core, and a hard drive (if you could call it that) cost $25k. Oh, am I dating myself?

Just added some photos.

Ckuke
 
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Your URLs appear to be malformed. I had to use the following instead:

http://www.mediafire.com/view/?830co9g2uhodx4v
http://www.mediafire.com/view/?e4rfz8kb3o2giwl
http://www.mediafire.com/view/?u3d41hxvhlnnm64

Direct links:
http://205.196.121.191/jvsltn77f2ag/e4rfz8kb3o2giwl/PCB+Component+Side.JPG
http://205.196.122.7/jtcecrrv0rdg/u3d41hxvhlnnm64/PCB+Current+Trans.+Side.JPG
http://205.196.122.17/b4n58yv9q12g/830co9g2uhodx4v/Finished+Device.JPG

Nice job, anyway.

Edit: It appears that our posts have crossed. I see you have already preempted my corrections.
 
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Here are the results of contruction of the eight PCBs. The first of the eight you can see in the photos above. That one fell on the side of too sensitive and was indicating some noise as well as signal - it was corrected by the potentiometer (adjustable sensitivity) alternate version of R2 (see schematic). I damaged one more PCB beyond repair by accident. The remaining six performed as planned and are currently in trials here and at area computer shops.

What remains is proof of the concept that Y-Sig is indeed the true current signal from the head positioning motor. I'm working on that. This will require finding a sacrificial SATA drive, so be patient.

More to come. Suggestions? Comments?

Ckuke

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


Here is the evidence for proof that Y-Sig is indeed derived from the voice coil motor (VCM) current (also referred to as the head

positioning motor current). Included (see links below) are two Virtins oscillographs of the Y-Sig LED Voltage derived from the VCM

current (top trace in red) and the Voltage across the VCM (bottom trace in blue). Various time constants due to the devices

themselves and the measurement instruments complicate the interpretation of the VCM Voltage. Only the rapid peak-to-peak rise and

fall lines of the VCM Voltage (blue trace) are of our concern since they reflect the actual head movements in opposite directions.


A fact needed for interpretation of the oscillographs is that current lags (begins later in time) than Voltage in an inductor - the

VCM inductance. Therefore, the red trace (LED) rising edge will occur after the rapid rise or fall on the blue trace (Voice Coil

Voltage) due to the characteristics of the inductance of VCM. A rising or falling edge of the blue waveform is followed by (at least)

one rising edge of the red (LED On) waveform. Multipe LED On pulses can occur due to overdrive (sensitivity too high) of the Y-Sig

sensor's characteristics - two (2) instances in the first oscillograph and enhanced in the second. This latter may be a benefit for

LED display purposes.


First oscillograph: http://www.mediafire.com/view/?iyw912ocxixtcxf

Second oscillograph: http://www.mediafire.com/view/?fnyr043bjp55cyf


My orginal question is now answered, by me. A SATA LED for each HDD now exists. It took awhile, but I think it was worth it. I hope you feel the same. Thankyou for your interest and patience. If there is enough interest, maybe someone will market the device.

Ckuke
 
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Unfortunately your gallery is "temporarily unavailable", so my additional observations are made without reference to your improved circuits.

Other than by winding a second turn over the inductor, I'm wondering whether you could improve the sensitivity of your circuit by adding a pulse stretcher. Of course this wouldn't actually make the circuit any more sensitive, but it would make small pulses more visible.

FWIW, I found this circuit:
http://www.eetimes.com/design/analog-design/4170028/Fast-simple-one-shot-pulse-stretcher-detects-nanosecond-events

As for adjusting the sensitivity, how are you doing this? I would think that you would need to adjust the trimmer to produce acceptable LED output during a sequential read so that track-to-track seeks would be detectable. Also, you may need to consider those users who set their AAM for minimum seek noise. This would reduce Y-sig even further.
 
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Hi again fzabkar. The problem with the first PCB was too much sensitivity. I compensated with the R2 trimmer alternate for greater offset and hysteresis. Oh, incidentally, the Mediafire.com URLs seem to work fine from my end. Also, the schematic URL is back several more pages from the photos.

For your convenience here's the schematic URL again: http://www.mediafire.com/view/?i2h64yyl9lhq9yf

I tried adding a one shot pulse stretcher to the original breadboard, but found that increasing the R1, C1 time constant (to what is shown in the schematic) accomplished the same thing - it's pretty well optimized. Initial reports from the devices in field indicate that they are working well on all SATA drives tested. At this point in my life (old) I'm comfortable with not knowing if I can see a single track-to-track seek. Maybe I can.

Ckuke
 
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I like everything about your design. It's simple, non-invasive, easy to install.

As for single track-to-track seeks, I'm thinking more of a full format requiring one or more hours which would consist of numerous small seeks. Would such a pulse train be visible? If not, would this be an acceptable limitation?

BTW, I can download your schematic, but neither Opera nor Firefox give me access to your gallery. I guess that's a limitation at my end, though.
 
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Try these:

http://i1048.photobucket.com/albums/s377/ckuke/th_c1b1cc10.jpg

http://i1048.photobucket.com/albums/s377/ckuke/th_76826caf.jpg

http://i1048.photobucket.com/albums/s377/ckuke/th_bfd87204.jpg

Let me know if these work.

Ckuke
 
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fzabkar there is no picture of the eight. Can show you the two that remain here. I'll be glad pull them out of the PC and include the picts here. All but the first look just like the "Finished Device" photo with the exception that the two here and some others have the old Molex connectors on one end. The others are out for trials in PC shops. I'm not sure what you want to see. Oh, maybe you want to see picts of the PCBs themselves. I can do that - I have some extras I can photo. Okay?

Ckuke


PCBs:

http://www.mediafire.com/view/?pd7rddhyjfsnypv

http://www.mediafire.com/view/?be3o8uqm0ur1px9
 
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Here is the evidence for proof that Y-Sig is indeed derived from the voice coil motor (VCM) current (also referred to as the head positioning motor current). Included (see links below) are two Virtins oscillographs of the Y-Sig LED Voltage derived from the VCM current (top trace in red) and the Voltage across the VCM (bottom trace in blue). Various time constants due to the devices themselves and the measurement instruments complicate the interpretation of the VCM Voltage. Only the rapid peak-to-peak rise and fall lines of the VCM Voltage (blue trace) are of our concern since they reflect the actual head movements in opposite directions.

A fact needed for interpretation of the oscillographs is that current lags (begins later in time) than Voltage in an inductor - the VCM inductance. Therefore, the red trace (LED) rising edge will occur after the rapid rise or fall on the blue trace (Voice Coil Voltage) due to the characteristics of the inductance of VCM. A rising or falling edge of the blue waveform is followed by (at least) one rising edge of the red (LED On) waveform. Multipe LED On pulses can occur due to overdrive (sensitivity too high) of the Y-Sig sensor's characteristics - two (2) instances in the first oscillograph and enhanced in the second. This latter may be a benefit for LED display purposes.


First oscillograph: http://www.mediafire.com/view/?iyw912ocxixtcxf

Second oscillograph: http://www.mediafire.com/view/?fnyr043bjp55cyf


My orginal question is now answered, by me. A SATA LED for each HDD now exists. It took awhile, but I think it was worth it. I hope you feel the same. Thankyou for your interest and patience. If there is enough interest, maybe someone will market the device.

Ckuke
 
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Hi,

Could not find it, so did the next best thing without schematic. Tried opening a trace and inserting a bridging wire loop to measure current but got over zealous and fried the PCB. Was more conservative with the second HDD. Many thanks for your help during this project.

Ckuke
 
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