charger in computer

[star882]

Do you have schematics for an AA Ni-MH charger that runs on 5v?
I want to install the circuit in my PC so it is powered by the 5vsb supply.
This is not as silly as it sounds as I found how to install a coffee maker in a computer here: http://pimprig.com/sections.php?op=viewarticle&artid=72 .

 

[0tr3b]

The USB port has a 5V pin.

 

[star882]

"The USB port has a 5V pin."
It turns off when the computer is off.
The 5vsb supply remains on at all times.

 

[PsycoBob[Q2]]

If your computer has a 'wake up from USB' option in the BIOS, turn it on. You may also need to change a jumper on the board to set USB to use 5vsb instead of the normal 5v rail. Mine does, dunno about yours.

5v chargers.... It'd have to be a 1 or 2AA. You MIGHT be able to get a charger that can run off a 12v car-adapter to work, if it's a smart-charger. Cheapo 'resisor-regulated' chargers would likely not work. It'd all be dependent on the voltage the IC's need to run. Older ones needed goofy things, like +-9v, but a newer one should be ok.

If you wanted to, you should be able to make a simple charger with a 2AA holder, a curren-limiting resistor, and a zener diode. "Battery-charged" voltage + "zener breakdown" = "5vsb" Measure the 5vsb rail first- some PSU's regulate it funny (slightly higher or lower than spec). Choose a resistor that'll keel current thru the batteries below both the max-charge rate, and below the 5VSB rating on the PSU (remember that the computer draws some, too...)

I'd try it, if I had a spare system. Might want to wait until someone says "Neat Idea, PsycoBob!" or "Dumbass! that'll make the magic smoke appear!"

My grasp of circuits is so-so.

 

[lux0]

If you draw current from the USB, according to specs, the USB controller in the peripherial device is supposed to report back to the OS how much current is being drawn.
If you connect other devices to the bus, they may cause too much current to be drawn, damaging the bus, or simply not powering up.

 

[star882]

I do not plan to use USB to supply power.
I plan to install 8 battery holders to charge Ni-MH AAs and AAAs(4 each).

 

[MrAl]

Hello,

Actually, that might not be such a bad idea.
A simple charger would consist of
a series diodes and dropping resistor for each
set of 2 batteries in series. The resistor
would have to be about 5 ohms, 5 watts.
The diode could be a cheap 1N5401.
With a 10 ohm 2watt resistor, the diode could be
1N4001. This would take longer to charge, but
would also reduce the load on the +5v computer
supply.
Using 4 such diodes and resistors you could
charge 8 batteries at a time.

If i were going to do this however, i would first
purchase a small switching power supply with
a nice current rating on the +5v output.
This way i could have the charger running
independently of the computer and avoid
any risk of damaging the computer just to
charge batteries.

Good luck with your LED circuits, and chargers:-)
Al