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Hard Drive Minumum Voltage Requirements

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May 19, 2009 5:38:21 PM

Hello,

I was wondering if anyone could tell me what the minimum voltage is required to operate a hard drive? The reason for this is that I need to set up a 12V DVR with a surveillance camera in a remote location and will need a battery system to provide power to the unit for a couple of days at a time (catching a thief). If anyone can help me I would really appreciate it.

Mark
a b G Storage
May 19, 2009 5:57:16 PM

a normal 3.5" drive requires 12 and 5 volts and consumes aprox. 5-11watts of power

+- 5% is ok anything over 13volts/ under 11.5 is somewhat out of bounds.




I would suggest a laptop drive as they require much less power.

what kind of dvr would you be using .. a usb powered laptop drive drive in an external enclosure comes to mind.

they use between 1 and 3 watts of power.
May 19, 2009 6:06:02 PM

Thanks rand.

I hadn't thought about a laptop hard drive. Maybe I will pick one up and see how it works out.

I was planning to use an Avermedia 1304NET SATA DVR, but I am open to suggestions.
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a c 353 G Storage
May 19, 2009 6:07:50 PM

for 3.5" desktop HDD's I believe the E requirements are:
+12V = +12V +/- 0.5 V (@ approx 2 Amps max)
+5 V = 5 V +/- 0.25 V

For 2.5" laptop:
+5 +/- 0.25V (Not sure on I, but should be a max of what a USB port can provide, or sligthly higher). For battery source a 4 Cell NiCd battery pack will be fine. Just parallel battery packs for Amp hours need,

For 12 V, you could use a motorcycle battery (12.6 VDC)

Look at wattage for the HDD. ie if 10 watts, divide by voltage for Amp/hr needed

10/5 = 2 Amp hrs so a battery with 20 Amp hour rating should last 10 Hrs
Bare in mind the 10/20 watts for the HDD is max and at idle is only a couple of watts which means battery will last much longer.
May 19, 2009 6:21:47 PM

Actually, I am going to use deep cycle marine batteries simply because of capacity even though they are rather expansive. The big thing is that while voltage is 12.6 or so fresh from the charger, they drop off and this is where I will run into trouble. It requires a much larger number of batteries to keep voltage above 11.5 volts than what is required if you can run the system on 10.5 volts.

The laptop hard drive is an excellent idea and I would like to keep the drive inside the DVR, connected to the SATA cable. I haven't even touched a laptop hard drive before, but I have built a number of desktop machines so I am ignorant as to the modifications needed to operate a 2.5" 5V drive inside a device that is designed for a 3.5" 12/5V machine. Not much, I would assume.
a c 127 G Storage
May 19, 2009 7:17:51 PM

A normal disk requires 30W+ to spin up, which is a pretty high requirement, its about the same as two laptops would use when idling, with their monitor still on. Ofcourse this 30W will only be needed for a few seconds, it does pose several problems. Laptop HDDs are much better in this, and SSDs don't have this problem. Also SSDs don't fail in the normal way, and are resistant to vibrations and temperature variations. This makes them excellent devices to integrate into embedded or portable systems, as their lifespan would be many times that of a HDD. a HDD need to be maintained; an SSD could function for many decades without any maintenance. Might be something to keep in mind.
May 19, 2009 7:27:56 PM

I thought about utilizing a SSD, however, because a DVR writes over and over to the same space before it actually records an event where movement occurs (when the system is set up for motion record of course), I am not so sure a SSD would be a viable option. The SSD would probably be a decent idea for cold weather recording though. The hard drive will more than likely not spin up very often unless you are performing a search.
a c 127 G Storage
May 19, 2009 7:36:51 PM

The "writing to the same sector over and over" doesn't apply to advanced SSD with controllers that employ a technique known as "wear-leveling". In essence it remaps the sectors that has been written alot to, with fresh sectors without the operating system or other hardware ever knowing. This way, you could write about 150GB every day for the next 10+ years or so, which is more than HDDs are specified to handle. The Intel X25-M has been verified to perform this task very well, although it doesn't come very cheap. Other SSDs might also employ a wear-leveling technique that is sufficient for your needs; just avoid the cheap SSDs (often under 32GB size) which have extremely simple controllers. These typically also have very low sequential speeds, like 16MB/s read and 8MB/s write, so they should be easy to spot.
May 20, 2009 2:59:12 AM

Get a 2.5" to 3.5" to drive adapter; it's basically nothing more than a tray and a connector and typically costs $4-8.

If the drive sits inside the DVR, the DVR is providing power to it.* You need to worry about supplying power to the DVR (not to the drive). If the DVR takes AC, you'll need an inverter to run from batteries. You probably want a unit that takes DC (e.g., uses an external power brick).

You'll need a DC-DC converter/regulator that will take your battery power and provide the right (stable) voltage to the DVR. (Trying to do that directly from the batteries is a losing proposition.) They are generally designed to take an input voltage range and provide a stable output. E.g., take a 6-18V input and produce a stable 12V output.

First step is to determine the DVR's DC voltage and power requirement. If you can't determine it ahead of time, the label on the power brick will show it. Next step is to find a DC-DC converter/regulator that will take an acceptable input voltage range--that is, what you'll see from your batteries--and produce the required stable voltage and power for the DVR.

Next step is get a power connector compatible with the DVR, then wire everything up.


* Edit: If the drive isn't in the DVR and you need to supply external power, the above still applies, only on a smaller scale. So first question should be: where's the disk and how is it hooked up to the DVR?
May 20, 2009 3:48:12 AM

Thank you.

The DVR is indeed a 12V DC unit, so it will readily operate on a 12 volt battery system. What you are saying about the regulator makes complete sense and I have already been considering it. I will be receiving the equipment in about a week and cannot wait to see how it all works out. I placed an inquiry to Avermedia today about their minimum voltage requirements to operate the DVR and the technical support people had no idea what would happen below 12 volts as their lab has never tested it under those conditions.


I suppose there is only one way to find out......... :D 
May 20, 2009 3:50:06 AM

And thanks to sub mesa for the input on SSD's. I would love to try one out, however, the minimum practical requirements for the hard drive is at least 250GB, making the whole exercise a little on the pricey side.
a b G Storage
May 20, 2009 5:36:49 AM

All the DVR's I've installed had the drives in the dvr, powered by the dvr. So all you would have to do is power the dvr and the camera. Camera's by the way take 12v and are extremely picky about having the right voltage. How far are you going to be from a power source ?
May 20, 2009 6:06:56 AM

The site is fairly remote with no practical way of running power to the system aside from batteries. The hard drive does indeed go inside the DVR. As for cameras, I did manage to try a 1/3" Sony CCD/DSP camera .01 LUX (no IR emitters), and it ran fine on the 10.5 volts/.3A that I measured in both daytime and night time situations.
May 20, 2009 7:45:58 AM

Cool. That the DVR takes 12V is great and keeps it simpler. I would hope and expect it has its own internal DC converter/regulator that can cope with reasonable fluctuations in input voltage (just like many of the pico/mini-ITX DC PSUs that use a power brick). In any case, if you need to add a regulator it should be reasonably cheap (assuming the batteries are decent and the DVR/cameras aren't too temperamental or power hogs :) .
May 20, 2009 5:27:27 PM

The DVR has a 3A draw according to the manufacturers specs, including hard drive and I will be using 3 225A deep cycle marine batteries, which should be overkill for a 72 hour period, so I imagine it will be fine. Guess I will know in a week or so :) 

And yes, I will be picking up a regulator as you suggested. Thanks for mentioning it.
a c 353 G Storage
May 20, 2009 7:52:25 PM

Only If your eletronics inclinded
A very simple way to regulate the the 12.6 V to say 12.0 V would be to take a NPN power transitor ( say rated at 10 Watts). connect a zenor diode from the base to Gnd and a 100 ohm 1/4 Watt resistor from Base to collector. E out = 11.7 to 11.5 V. (diff is Si vs Ge)

This would regulate as long as Batt = 12.6 V. As batt voltage drops below 12 V then E out will be Batt Voltage - approx 0.5 V.

If everything will work at say 11 VDC, then use a 11 Volt zener Diode.

Much less power loss than using a power inverter.
a b G Storage
May 20, 2009 10:33:30 PM

RetiredChief said:
Only If your eletronics inclinded
A very simple way to regulate the the 12.6 V to say 12.0 V would be to take a NPN power transitor ( say rated at 10 Watts). connect a zenor diode from the base to Gnd and a 100 ohm 1/4 Watt resistor from Base to collector. E out = 11.7 to 11.5 V. (diff is Si vs Ge)

This would regulate as long as Batt = 12.6 V. As batt voltage drops below 12 V then E out will be Batt Voltage - approx 0.5 V.

If everything will work at say 11 VDC, then use a 11 Volt zener Diode.

Much less power loss than using a power inverter.

The problem with that solution is that it doesn't actually address the main problem, which is that as the battery loses power, it will drop down to under 11.6 volts. Therefore, the regulator would need to step up the voltage if the power sagged, as well as step down the voltage if it was too high. That is a significantly more complex circuit.
a c 353 G Storage
May 20, 2009 11:24:56 PM

cjl
Very good comments and I agree in general with your comments. My SIMPLE (I would make it a little more complex) ckt would not booast low voltage, High voltage not a real problem as max DC from lead acid 12.6 (reason old vacuum tumes used a 6.3/12.6 Volt filiment). 3 Marine batteries in parallel should last quit a while with only 3 - 4 amps current my QUESS is maybe in excess of 100 hrs - Only used 100 AmpHr battery and 3 Amp current drain

A DC-AC-DC converter will run the batteries down much quicker and both suffer from a low input unless a low input protection circuit is used.

A simple cut off relay using a 10 Volt zener could be used to remove Batt power when voltage drops below 11 V
May 21, 2009 4:02:42 PM

Good points cjl and RetiredChief. I decided to go forward with the regulator and ordered one from my battery supplier. They feel it will work well for the system I am putting together. If it fails miserably, it's back to the drawing board.

I will report on how things turn out (hopefully without a youtube link to a fire).
June 9, 2009 9:33:27 PM

Great success!

I installed a 2.5" WD Scorpio Hard Drive with adapter plate and a 10-30V DC to 12V DC "step up/step down" regulator, attached it to a 12V car battery (12.1V when I hooked it up) and with current battery voltage at 11.5V, the regulator is still putting out a steady 12.08V. Looks as though the system will be a winner for my application.

Thank you to everyone for your input. :) 
a b G Storage
June 9, 2009 11:18:04 PM

The ATX spec. states maximum tolerance for 12V is 10% (lowest being 10.8V) while for 3.3V and 5V it's 5%. That said, the spin up voltage (and hence wattage if current stays the same) might be a little different between HDDs.
October 31, 2009 12:47:35 AM

Mark_Alberta said:
Great success!

I installed a 2.5" WD Scorpio Hard Drive with adapter plate and a 10-30V DC to 12V DC "step up/step down" regulator, attached it to a 12V car battery (12.1V when I hooked it up) and with current battery voltage at 11.5V, the regulator is still putting out a steady 12.08V. Looks as though the system will be a winner for my application.

Thank you to everyone for your input. :) 

!