Sign in with
Sign up | Sign in
Your question
Solved

Can I modify a USB to provide 2A for my portable hard drive?

Last response: in Storage
Share
December 12, 2011 8:24:01 PM

Hello,
I have 2 Philips DVD players with USB input. One will power my 2.5 Toshiba portable 500gb drive and the other will not. I am planning on hard wiring a USB female pigtail out the back of the case so I won't have a cord coming out the front. What I am wondering is if I can mount a 5V 2A supply inside the case and wire the USB cable power to that when the data wires are connected to the DVD player's data pins. I could get an external HD enclosure with power input but then there are extra wires and the drive would stay on after I shut down the DVD via remote.

Thanks,
Peter
a b G Storage
December 12, 2011 9:40:45 PM

You could do that but make sure that the power supply has a current limit in case the supply rails are shorted. 2A is a bit much for the USB connector particularly if there is any surge when you insert the device.
m
0
l
December 13, 2011 4:33:55 AM

From pjmelect: "make sure that the power supply has a current limit", good idea, I will probably just fuse the output. I'm sure I won't even draw 500 mA, but the 2A supply is cheap and convenient.

I just wasn't sure if I would have any ground loop issues or any problem grounding negative output to chassis.

Thanks again,
Peter
m
0
l
Related resources
a b G Storage
December 13, 2011 5:25:49 AM

I don't understand what you are trying to do, the USB port can supply 500mA but a unpowered USB hub can only supply 100mA per port
m
0
l
December 13, 2011 12:19:27 PM

The DVD player USB port is apparently not capable of delivering 500mA and won't power the drive. I am going to add a powersupply and connect it to the power wires of a USB female cable. I will cut one end of the USB cable and connect the power wires to the power supply I am mounting inside of the DVD player and then connect the data wires to DVD player's original USB input. I will end up with a USB input to the DVD that will power any drive and I won't add any clutter.
m
0
l

Best solution

December 13, 2011 1:35:07 PM

Computer Engineer here:
Here's what I'd do:
Step 1: Acquire power supply (adjustable buck converters can be found on eBay for cheap. otherwise digikey or mouser could have what you need)
Step 2: Test power supply. Use a voltmeter to make sure it outputs the right voltage. Test it under some load to see how it works. If the voltage output remains satisfactory, test it powering the hard drive.
Step 3: Connect the power converter to the voltage source of the DVD player.
Step 4: See if the hard drive can be powered
Step 5: Keep the USB ground, D+ and D- wires connected as usual. Connect the 5V output of the regulator to the 5V that goes to the HDD, making sure that you don't connect it to the 5V of the DVD player (bad things will happen if you do so). Connect the GND output of the power supply to the GND of the USB

If you have any questions let me know
Share
December 15, 2011 2:28:43 AM

killer squirrel, that is pretty much what I had planned. I ordered an AC to DC converter, (power supply for a PSP)http://www.amazon.com/dp/B001MW3TLM/ref=pe_175190_21431..., and figured I could add a relay (triggered by the DVD player's 5V USB output) connecting it to the DVD player AC input. I am pretty confident the supply will power the drive, my biggest concern is hoping that nothing bad will happen when connecting the ground as you mention at the end of step 5.

I also realised that the supply is a charger/supply and wonder if the current sensing circuit is in the charger or the PSP.

m
0
l
December 15, 2011 1:29:03 PM

Nothing should happen. Current requires a loop in order to flow. By connecting the grounds together, you are basically just maintaining a reference voltage.

Although it wouldn't hurt to probe two lines with a voltmeter, just in case. If there's a substantial difference, use a small (10-100ohm) resistor to try to equalize them. By using V=IR across the resistor, you'll be able to see how much current is flowing between them. Theoretically this should be zero.

I'm pretty sure lithium battery chargers have some type of sense line. Since that is using a barrel plug (with only two connectors), I'm pretty sure that it's just a power supply.

Also check the voltage and current on the relay you're planning on using. I've seen some that require an amp on the control line in order to close the circuit...

m
0
l
a b G Storage
December 15, 2011 11:53:30 PM

If your power requirement is only 500mA then why don't you use a powered USB hub? This will provide 500mA per port as well as giving you some spare ports and does not require you to modify your equipment.
m
0
l
December 16, 2011 1:31:45 AM

pjmelect said:
If your power requirement is only 500mA then why don't you use a powered USB hub? This will provide 500mA per port as well as giving you some spare ports and does not require you to modify your equipment.

I considered that but it all has to fit in a cabinet with limited space. I also want it to power down the drive when the DVD player is off, the drive will remain connected most of the time. I had also planned on modifications just to have a rear USB output.

Killersquirel, thanks for all the input, I will let you know how it turns out.

-Peter
m
0
l
December 16, 2011 1:33:40 AM

Best answer selected by peterp11.
m
0
l
December 18, 2011 4:31:20 PM

I thought I had it figured out, now I am stumped.

I have 2 Toshiba 500gb drives, 1 USB 2.0 and 1 USB 3.0.
I have 2 identical Philips DVP3560 USB input DVD players.

The USB2 drive will work one one player, it started to work on the other but then started to click and will only click on that player ever since.

The USB3 drive only clicks on either player.

Assuming it was a current supply issue, I made my test with a 2A supply connected to the power wires of my USB extension cable and left the data pins intact.

The supply maintains voltage between 5 and 5.3V but neither drive will work with either player. The test cable will work with a flash drive (which also worked before). The USB2 drive which worked with one player will now spin but click randomly and is not recognized by that player. If I hook it direct to the player's USB input, it works fine as before. I also tried it with an unalterred extension cable and it only click with that one as well. The unaltered cable will work with a computer USB but the cable with external power will not work with the computer.

It seems the supply is incompatible in some way. With the USB2 drive, the amperage would reach .5 and then drop to .2 just as the drive clicked.

I wonder if a USB wall plug charger might work or if I will have to go to a USB hub after all.

m
0
l
!