Monday, August 31, 2009

Powering a 12 Volt Router from USB

USB Adaptor 5 Volt to 9 VoltConnecting the HUAWEI E169 3G USB modem to the Kogan Agora Netbook is proving harder than expected. While there are descriptions on the web of simply plugging the modem in and restarting the computer, the Kogan does not seem to recognise the device. Some manual modifications of setting have not helped. So I decided to take a different approach: when plugged into the Huawei D100 3G Router the modem works fine with the Kogan. The settings for the modem are stored in the router. This has the added advantage of the firewall in the modem and that the device can be shared by several computers.

But the router runs on 12 Volts from and mains power supply. How would I use it when away from a power socket when the Netbook is running on batteries? My first thought was to run the router on the power from a USB plug of the computer. I found that the Kogan's USB sockets supply plenty of power, being able to run an external DVD drive or hard disk. With my previous laptop I had to use two USB sockets to get enough power for an external drive.

The catch is that no one seems to make a USB to 12 Volt adaptor (there are plenty of 12 Volt to USB adaptors). In fact there are numerous web postings saying this is not possible. It is possible, but needs extra electronics to turn the 5 Volts supply by the USB socket into 12 Volts.

Digital MultimeterNot being able to find a 12 Volt adaptor, I thought I would make the problem easier by trying a lower voltage. Most digital electronics actually run on 5 Volts or less. The 12 Volts supplied to equipment is converted down. So first I tried the router at 5 Volts, using the USB adaptor cable which came with the external DVD drive. This was after I checked the voltage and polarity of the power with a multimeter). This did not work, clearly more than 5 Volts was needed.

Previously I had run a router designed for 12 Volts on a 9 Volt supply, with no problems. So I tried this with the Huawei D100 3G Router and found it works fine on 9 Volts (it has been running for 12 hours this way).

So then I looked for a USB to 9 Volt adaptor. There were numerous queries about such devices on the web and replies saying it was not possible. But I found one about a "USB Power Supply for Video Sunglasses" which used a DC-DC converter (voltage converter) from a phone charger accessory kit described as a "9V Nokia Booster for Wireless Phone Charger".

The booster is a small black box with a USB plug on one end and a USB socket on the other. The device converts 5 Volts to 9 Volts at 300 mA and is designed for charging old Nokia mobile phones. The instructions warn this should only be used with a 9 Volt device: plugging a standard 5 Volt powered USB device into the unit could damage the device.

As I already had a USB adaptor from the DVD which plugs into the router, it should be a simple matter to plug the voltage booster into the Netbook, plug the USB adaptor cable into that and that into the router. But where in the world do I buy such an adaptor and how long will it take to get to Australia?

As the device was for a Nokia phone, I looked at the Nokia catalogue, which had a "Nokia Charger via USB port CA-100". However, this appeared to be for newer phones which use a lower voltage. I looked at Ryda, who sell a "Nokia CA-70 USB Data Cable with Intergrated Charger". This looked more than I needed and I was still not sure it would supply the needed voltage.

After more searching I found the "Charger Sony K750 W830c w958 Z558 M608 W300 J220 K310" offered on Ebay by Swamp Industries. This appeared to be the same adaptor kit as used for the video sunglasses. I checked to see the company details on the web to see how long this would take to import into Australia and found the company is based in Canberra (where I am). Also I found the kit includes an Australian mains to USB power adaptor, which would be handy. On the company's own web site the kit is described as "Universal USB Mobile Car Wall PC Charger Nokia, Blackberry" and was half the price on the company web site as on eBay. So I ordered one.

It will be interesting to see when it turns up. It is also curious that having searched the world online, I found the product I wanted offered by someone a few kilometres away. I was tempted to phone the company and ask to collect the unit in person, but this is probably a part time mail order company with no shop. I do have the satisfaction of having a name to put to the company, as when I paid via PayPal, the system gave me the person email address of who was getting the payment.


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Steve said...

The recall is a small black box with a USB connector on one end and a USB connector on the other. The device converts the 5 volts to 9 volts at 300 mA and is designed to charge mobile phones older Nokia. The instructions warn that should be used with a 9 volt unit

toobsaus said...

So Tom, did the USB to 9V power the router OK ?

Tom Worthington said...

toobs said October 26, 2010 8:19 PM:

>... did the USB to 9V power the router OK

No. The voltage is high enough, but the router uses up to 500 mA for a few seconds when it first starts up. When I turn the router on it starts to boot, then the green light on the USB adaptor turns red (presumably to indicate it is overloaded) and the modem goes off.

I tried adding a 80 uF capacitor, but this still did not work.

My next option would be to use two 9Volt power supplies connected in parallel, from two USB ports.

Tom Worthington said...

After five years, I finally found a "USB To 12 Volt Power Supply" to run my router from the laptop.