charge by usb

Ok this is probably a simple question but how come I can charge my cell phone from a usb charger but when I use a voltage regulater at 5v out with a usb connector as the output plug it won't charge?

Does the pc send like a command to the phone? Or must I supply power to the d+ and gnd to the d- pins also?

The are 4 pins on a usb connector v+, v- and the other 2 data lines. How would I make this work? Sorry if this is confusing

The phone may request the higher current allowance of 500mA and will not charge until it gets permission. Is there a DC socket you could hook into?

Mike.

I don't own a AC adapter (dc wall plug) but im going to try to get the specs for it.

Have you ever seen those single AA cell jumpstarters? They are supposed to let you use your phone for a short period of time... well I want to make that but on a slighly larger scale. With about 4-8 AA cell 4 in series or 8 where 2 are in parellel and there are 4 sets so if its 2500 mAh then it should be roughly 5000mAh which would give it a nice long run lol

I have one of these charger things floating around somewhere I'll track it down and take some photo's of the circuitry, unfortunately I'm not good enough to identify everything lkely to be on it and so cannot give you a schematic diagram.

Unit Info
Brand: Energizer
Power Source: 2x AA Batteries
Compatible Phone Models: Motorola type small usb input
Charge Time: ~2 minutes

Mercur

Cool thanks a bunch!

Best images I have at the moment.

Here are the best shots I could get with a D2X DSLR
I'll try using a phonne camera to get in under the jack but no promises.
There you are if you want more I can try and get them.

USB is 5.0V. An ordinary 5V regulator (7805) needs a minimum input of 7V or its output voltage is not regulated and is too low.

Nice pictures... I think I need to up my mA a bit ... how would I do that? (Inductor?)

USB provides 100mA but you can ask the processor to give you 500mA. No more.

audioguru said:

USB provides 100mA but you can ask the processor to give you 500mA. No more.

Click to expand...

Just Out of curiosity, How one can do that?? ( i mean ask the processor to give more power??)

Cry_Wolf said:

Just Out of curiosity, How one can do that?? ( i mean ask the processor to give more power??)

Click to expand...

I don't know how to program it to ask for max current.

A 7805 is supposed to give upto 1A ... depending on input I assume... but if input is 4 AA's that 4.8v (1.2v ea.) @ 2500mAh that's 2.5A for 1 hour I think... so... 2.5 hours @ 1A if so why can't I get this to work by just supplying power to the phone?

That's why I asked if power is going to the actual data lines of the usb ... soft of like a switch to tell phone usb is plugged in and its time to take the power from the +/- lines.

Understand any of that? Lol

Again, a 7805 needs a minimum input voltage of 7V. It won't work if its input is only 4.8V.
It gives an output current up to 1A only if its input is 7.5V or more and 1A.

I don't think that you have to ask for more current from the usb port. It will give you 5V @ 500mA what so ever. I am saying this because i once made a programmer that used the 5V and about 350mA from the USB!

Am i missing some thing here??

Hi there,


You can draw up to 500ma from the USB port but you are NOT supposed to do this.
The correct protocol is to take up to 100ma, then negotiate the connection to ask
the system for another 100ma, then another, until the max of 500ma is reached.
Things will still work without this negotiation, but the system will not know that
your device is drawing 500ma and that is the whole point as something could go
wrong if another USB device asks for more current or another device like this
is plugged in...it depends on your system though.

As far as getting the 7805 regulator to work (other post), you need to connect
more than 7.5v into the front of the regulator in order to get 5v out. This is
because the regulator drops some voltage too. There are LDO regulators (low
dropout voltage regulators) that can work down to about 5.5v, but you'll
have to look that up on the web. In any case, if you connect cells that total
up to say 9v dc you will surely get your 7805 to work just fine. Remember to
double check the output voltage first though before connecting to the phone.