# How to use BSNL  broadband  landline modem when there is power off..?



## mdp (Apr 23, 2010)

Hi friends..

I am planning to purchase laptop due to 7-8 hours of load shedding in my city.

I  will use laptop in office and will require inter net continuously..

I have BSNL landline modem presently.It requires 12V DC power supply.

 In case of power failure how can i use net..? 

is there any kind of adopter available in market which will take power from USB of laptop and will convert to 12 V DC and can be used to power up modem..?

Any other way..?


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## ajayashish (Apr 23, 2010)

BEST WAY.. i can think of is BUY A UPS/


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## Aspire (Apr 23, 2010)

Get A Solar Panel?


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## sriharsha_madineni (Apr 23, 2010)

Back-up UPS is a good option as said above


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## PraKs (Apr 23, 2010)

@OP

I too had same idea of powering modem from USB.

There was huge thread on it. Have got solution of powering Airtel Modem from USB


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## infra_red_dude (Apr 24, 2010)

Theoretically that would not work, because USB is a 5v source. 5v-to-12v step up adapters may work but I don't think the current requirement is satisfied (500mA is the max. and the modem would definitely require more). In short, I would refrain from doing this.

I would anyday, got in for cheap UPS to power the modem. Since the modem/router consumes quite low power, you can get like 4-5 hours (or even more) backup for your modem.


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## mdp (Apr 24, 2010)

I have 600VA Wipro (WEP) UPS.How long it will last?

can any body answer who practically uses modem on UPS..?

why does BSNL dont introduce modems running on 5V USB power supply..?

to whom should I give feedback in BSNL..?


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## infra_red_dude (Apr 24, 2010)

mdp said:


> I have 600VA Wipro (WEP) UPS.How long it will last?
> 
> can any body answer who practically uses modem on UPS..?
> 
> ...


It doesn't matter. Just a search for 5V modems gives a current requirement as 2.0A which is too high. This kind of current can never flow through USB. That's 4 times the max. current (500mA). The max. wattage supplied by your USB is 5V * 500mA {or 0.5A} = 2.5W (roughly). Most modems have a power rating of a minimum of 7W. So your USB port cannot supply enough clean power.


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## PraKs (Apr 24, 2010)

@infra_red_dude'

There are people who claimed that Airtel modem works by powering from USB port.

I guess its 220BX version which takes 5v power.


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## infra_red_dude (Apr 26, 2010)

PraKs said:


> @infra_red_dude'
> 
> There are people who claimed that Airtel modem works by powering from USB port.
> 
> I guess its 220BX version which takes 5v power.



You may check out the current rating of the modem before you plug into the USB port. End of the day you want to use the modem during power cuts, but if the modem itself sucks too much power from your laptop then the whole purpose is defeated!

I believe you can use a Y-USB cable for more power (they are in parallel; remember Kirchhoff's Laws? currents in parallel get added)


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## ajayashish (Apr 26, 2010)

i think for one the modem powered by USB comes out... people will ask for modem which dont need any power as well... Crazy people always needs new things to make their life easier... 

Even if u power ur modem with USB you will drain ur laptop battery... which in turns shorten the battery life... i think... UPS is cheaper than a Laptop battery


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## PraKs (Apr 26, 2010)

@ajayashish
Techie wishes are never over 

Idea is to keep modem on for 10-30 mints by taking power from USB/Laptop battery.
I guess it will not be much problem when other USB devices like ext HDD/mouse are not connected.

@infra_red_dude 
Can you post pic of Y-USB cable ? Any idea what rating Airtel 220BX requires ?


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## gopi_vbboy (Apr 26, 2010)

why dont u get a inverter for home

i have a 130AH battery -800VA inverter...connected to all lines exept fridge,a/c,heater,etc heavy loads....

so go for inverter with dedicated wiring at home


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## ankushkool (Apr 26, 2010)

I use my moden on ups, althoigh i m using tikona... but 7-8 hrs... is it at once or in intervals?


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## PraKs (Apr 26, 2010)

Well Inverter costs 10000 Rs

UPS costs around 2000 Rs

USB Cable costs 100 Rs...

Make your choice


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## 6x6 (Apr 26, 2010)

if you have to run only modem from UPS, better option is to take out 12V DC from battery terminals, and keep the UPS off. it will run Modem for ~10 Hours. as modem needs 12V@0.7A and UPS battery is 7AH. no need to step up from 12V DC to 220V AC and then step down 220V AC to 12V DC again, power is wasted in both operations. 

another option is using small 12V battery with small charger, setup may cost <Rs500/- and backup time will be 2-4Hours depending on AH capacity (naturally battery cost will also depend on AH capacity)


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## infra_red_dude (Apr 27, 2010)

PraKs said:


> @infra_red_dude
> Can you post pic of Y-USB cable ? Any idea what rating Airtel 220BX requires ?


*www.toshibadirect.com/images/ui3/accessories/toshiba-usb-y-cable-ba82010-300.gif

Absolutely no clue about the power requirement of any modem/router!



6x6 said:


> if you have to run only modem from UPS, better option is to take out 12V DC from battery terminals, and keep the UPS off. it will run Modem for ~10 Hours. as modem needs 12V@0.7A and UPS battery is 7AH. no need to step up from 12V DC to 220V AC and then step down 220V AC to 12V DC again, power is wasted in both operations.
> 
> another option is using small 12V battery with small charger, setup may cost <Rs500/- and backup time will be 2-4Hours depending on AH capacity (naturally battery cost will also depend on AH capacity)


I would never do that. Without a regulator circuit I would never connect anything to the bare battery terminals.


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## PraKs (Apr 27, 2010)

@6x6
Uh, looks too scientific, it may blast modem too, Why would someone risk taking battery out of UPS & connect openly.. It will look like garage in home 

Anyone interested in powering up Airtel modem using USB port of laptop ?


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## icebags (Apr 29, 2010)

infra_red_dude said:


> *www.toshibadirect.com/images/ui3/accessories/toshiba-usb-y-cable-ba82010-300.gif
> 
> Absolutely no clue about the power requirement of any modem/router!
> 
> ...



wrong..... the 12 volt battery can supply ~12v max with constant DC supply. there should not be any problem running a 12v modem from the 12V storage cell, since there is no current fluctuation from battery, just constant voltage decay from 12v to downwards .. which should last ~8 hrs before the battery fails to supply required voltage for modem ..

then only the situation may go wrong.... modem components may heat up a lil / do malfunction stuff cause of low voltage.

its good choice to run 5v modem from a 12v storage cell, driven by a simple 5v voltage regulator from class 12 physics book tho.


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## infra_red_dude (Apr 30, 2010)

icebags said:


> wrong..... the 12 volt battery can supply ~12v max with constant DC supply. there should not be any problem running a 12v modem from the 12V storage cell, since there is no current fluctuation from battery, just constant voltage decay from 12v to downwards .. which should last ~8 hrs before the battery fails to supply required voltage for modem ..
> 
> then only the situation may go wrong.... modem components may heat up a lil / do malfunction stuff cause of low voltage.
> 
> its good choice to run 5v modem from a 12v storage cell, driven by a simple 5v voltage regulator from class 12 physics book tho.



It's not like it will blow up the appliances. I would still never use anything directly without a regulator. Connecting appliances directly to local batteries is the last thing I'd want to do!


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## rsk11584 (Apr 30, 2010)

6x6 said:


> if you have to run only modem from UPS, better option is to take out 12V DC from battery terminals, and keep the UPS off. it will run Modem for ~10 Hours. as modem needs 12V@0.7A and UPS battery is 7AH. no need to step up from 12V DC to 220V AC and then step down 220V AC to 12V DC again, power is wasted in both operations.
> 
> another option is using small 12V battery with small charger, setup may cost <Rs500/- and backup time will be 2-4Hours depending on AH capacity (naturally battery cost will also depend on AH capacity)



Even thought the battery when directly connected will provide a backup of 2-4 hours to the modem, what about the backup for laptop??????????

Depending on the company and batterys health the back up can be anything. SO better use a UPS, to directly connect to laptop and modem both, so that when laptop battery  begins to run out of juice the UPS can juice it up. Also do check before buying UPS, because some companies make their UPS as such that if there is no good amount of power drawing from it it will shutdown, I had one in my friends home, whenever he ran only Modem in his UPS it used to shut down automatically but when he connected PC n modem both to UPS it worked fine for the 20 mins or so. He told since the Modem draws very less power the UPS thinks there is no device drawing power from it and autoshuts down, thinking UPS eh


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## deepak2010 (May 3, 2010)

Buy a 12V Battery (SUNCA) and Compatible Charger for it. Battery will cost you around Rs.200.  Configure it and It will give u enough backup for your modem.


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## gagan007 (May 4, 2010)

I agree with deepak...being a techie you should not be afraid of doing experiments...moreover it does not affect any instrument/gadget, it is the best and cheap option. I have made many small scientific projects during my school days using such setup...hardly broken anything...


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