USB Cable and Battery power

Buzzbomb · Post by **Buzzbomb** » Mon May 04, 2009 9:11 pm

Ok guys.. I have another hare brained scheme.

I have one of those dinky little 3.5 inch LED Photo frames.
What I want to know is have any of you used the USB connectors connected to a battery ?

USB is only 5 V, so that is ok and my research tells me that Pin 1 is the 5V+ and Pin 4 is ground.. no problem so far.. well I dont think so.

So if I cut the cable (PC End) and connected up an appropriate circuit to give 5V etc.. is there any reason why this would not work?

Don't forget.. I am one of those guys who can supernova a LED

Cheers Brian

JadedMonk · Post by **JadedMonk** » Mon May 04, 2009 9:21 pm

In theory it sounds great!

A couple of thoughts though,

Make sure the frame can run on USB. A dinky unit I bought for Mother's Day one year can only charge and the display sleeps when connected. Major Fail.

Make sure you can supply enough amperage. This is getting awfully close to the limits of my knowledge, but the required current might drain your battery awful quickly.

Cheers!

JM

Pat Amaral · Post by **Pat Amaral** » Tue May 05, 2009 1:51 am

Brian,

I don't know which brand/model frame you have but typically, those frames
don't get their power from the USB cable. It would be self defeating and
redundant for the frame to rely on power from the computer to operate.

The cable is just used to transfer pictures from your computer to the
memory card in the frame. It's been my experience that the frames run
off internal batteries or a wall wart.

I guess my answer to your question is I don't think connecting the 5v and
gnd wires from the USB cable to a battery would do anything at all. Of
course, I could be wrong.

Chacal · Post by **Chacal** » Tue May 05, 2009 6:52 am

USB: 5V ± .25V / 100mA (low power mode: keyboards, connection to printers, thumbdrives etc.) or 500mA (high power: USB-powered fans, lights, charging iPods etc.)

Technically, if the Frame is powered by USB, it needs a high power supply (500mA).

I wouldn't just snip the cable away: I would build a battery holder and put a USB plug on it. The problem is that with standard 1.5V batteries, you can have either 4.5 or 6V, which fall outside USB's tolerances. With 1.2V rechargeable batteries, you can go to 4.8V, which is nicely within the tolerance, though the voltage will very quickly drop below that. You may build it up to 6V and drop the voltage with a resistor. All batteries you'll find will give you more than the 500mA required for high power USB devices, so you're good on that regard.

But why do you need battery power? Is it just so you don't have to have the computer on and the frame connected to it, or do you intend to use the thing on a model? If it's just to keep it separate from the computer, there are USB power providing wall warts (some quite petite) which can do the trick with no hassle, without gobbling up batteries.

Buzzbomb · Post by **Buzzbomb** » Tue May 05, 2009 7:10 am

Thanks Guys.
This is a small 3.5 inch by Digitech
Pat, this one does have USB power capability (as well as a wall wart, which used the same small USB type connection).. surprised me too, it chugs away nicely using the USB power options which made me wonder about the battery thing.

It is 500mA so in the high end, so it will chew batteries.

Chacal, I agree with the USB plug thing and I found an idea with using 4 x AA cells and a 5V 7805 voltage regulator which should work.

The scheme behind all this is as follows.
I have one of Stargazers Bladerunner Spinners and I want to display it flying in front of a building with the large billboard... this is where the Photo frame comes in, using its slide show function.
It is for a model show and power is not guaranteed so I want the option to power by batteries, even a couple of hours is enough with rechargeables.

Anyway I will give it a go and get back to you with the results.. or a photo of a smoking photo frame in the bin

Thanks again