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Powering Modem With USB.

Question asked by Abhishek Rawal in #Coffee Room on Jul 28, 2013
Abhishek Rawal
Abhishek Rawal · Jul 28, 2013
Rank A2 - PRO
I am trying to power my ADSL2+ modem with USB rather than adapter.
Behind the modem, in the specification it's mentioned i/p : 5V DC & this is same amount of power USB draws, right ?
Then also, I am unable to power on the modem. What could be the reason ?
I am using the USB cable the same we use to power Arduino. As shown in image.

2013-07-28 16.32.43 Posted in: #Coffee Room
lal
lal · Jul 28, 2013
Rank A3 - PRO
The voltage could be same. But, then it depends on the current modem draws too. Check the current output indicated on the modem's adapter. The maximum current output of USB port is some where around 700mA or even less. Without enough current output, the modem will not get sufficient power to power up.
Jeffrey Arulraj
Jeffrey Arulraj · Jul 28, 2013
Rank A2 - PRO
Modem needs minimum power to kick start even if your voltage his higher and your current rating is lesser the power required is not met

Pls post the current rating given in the adapter that will easily tell us what can be done to overcome this issue
Abhishek Rawal
Abhishek Rawal · Jul 29, 2013
Rank A2 - PRO
Conqueror
Pls post the current rating given in the adapter that will easily tell us what can be done to overcome this issue
I/P : 100-240V ~ 50/60Hz 0.3A
O/P : +5V --- 1A
lal
lal · Jul 29, 2013
Rank A3 - PRO
ah! There you go. The modem doesn't switch on because your USB port can't deliver 1A output.
Abhishek Rawal
Abhishek Rawal · Jul 29, 2013
Rank A2 - PRO
lal
ah! There you go. The modem doesn't switch on because your USB port can't deliver 1A output.
Anyother way that I can help me to switch On the modem with USB ?
lal
lal · Jul 29, 2013
Rank A3 - PRO
Not quite sure about that.

I read about a software by Asus which helps increase the USB current output a while ago. It was used to charge iPhones which needed higher current output to charge from a USB communication port.

I was thinking about a weird idea of paralleling two USB communication ports from different hubs 😁 Of course not the data lines! Hmm, not sure if it will work at all.
Jeffrey Arulraj
Jeffrey Arulraj · Jul 29, 2013
Rank A2 - PRO
Why not implementing a current boost circuit to increase the current That will solve this issue for sure Mate

Have a good time trying it out
Harshad Italiya
Harshad Italiya · Jul 29, 2013
Rank A1 - PRO
lal
Not quite sure about that.

I read about a software by Asus which helps increase the USB current output a while ago. It was used to charge iPhones which needed higher current output to charge from a USB communication port.

I was thinking about a weird idea of paralleling two USB communication ports from different hubs 😁 Of course not the data lines! Hmm, not sure if it will work at all.
Somewhere I heard about External powered USB HUB you can use it as it will give you more current but again you must have to use one adaptor for HUB so why not use it for your MODEM? 😀
lal
lal · Jul 29, 2013
Rank A3 - PRO
Yeah, right. An external powered USB HUB would be same as using the adapter to power the modem.

Well I read this, the connected device need to negotiate with the usb port to obtain more current. Else a normal usb communication port would supply only 100mA. By negotiating with the port, the device can draw current as high as 500mA (I don't know if it is possible to obtain more than 500mA by this way). I'm thinking may be the modem isn't made to negotiate with the USB port since it is expected to be powered from an external adapter.
Ashraf HZ
Ashraf HZ · Jul 30, 2013
Rank A2 - PRO
Use the +5V rail of your PSU, if there is 😁 Be sure to add resistors to limit current of course.

Or, use the existing +12V rails with a 5V voltage regulator.

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