power amp

[benji]

im building a robot that can charge stuff like batteries ....etc
the robot is able to detect how much voltage should it provde
now the problem is that i need a power amp so i can provide big currents (im fine with 1 amps at 5 volts)
5 volts is my maximum voltage to provide

anybody knows a good power amp IC ?
is it ok to use audio amplifier IC ? im not sure if they can supply dc current ..

[ArcMan]

Here is a simple battery charging circuit used for constant-current battery charging.  Check out page 7.

http://www.sparkfun.com/datasheets/Components/LM317.pdf

I use this circuit to charge my NiMH batteries.  Works great.  Just make sure that you set your current to C/10 or less to avoid venting when the battery becomes fully charged. C is the battery capacity.  For example, if you are charging 2000 mAh batteries, set your current to 200 mA or less.

[benji]

i know about the lm317 ,,the problem with it is that i want to supply low voltages also ,,like 0.5 and 0.3 volts in some applications
and the lm317 has a minimum out of 2.5 i guess
i need a variable source from 0 >> 5 v

[TrickyNekro]

eeeexxxx.....

Try PWM a MOSFET.... and read on output...

You can do that with a DS2438.... not to be proud and all that stuff have a look at my tutorial...
Won't help you much with what you want but it will be a good guide on the IC...
The IC can display sum of current in or out of the pack... but I don't include that function..... yet......

[ArcMan]

i know about the lm317 ,,the problem with it is that i want to supply low voltages also ,,like 0.5 and 0.3 volts in some applications
and the lm317 has a minimum out of 2.5 i guess
i need a variable source from 0 >> 5 v

The LM317 has a minimum output voltage of 1.25V, but that's as a voltage regulator.  When used as a constant current battery charger, output voltage of the circuit doesn't come into play.  You need to understand how the LM317 works.  What it does is maintain a voltage of 1.2V between its Output and Adjust pins.  Take a look at the circuit diagram on page 7, Figure 9 - the 50 mA constant-current battery charger circuit.  Placing the 24 ohm resistor between the Output and Adjust pins produces 50 mA of output current because (24 ohm) * (50 mA) = 1.2V.  So you can even tie the output directly to ground (meaning 0V at the output of your circuit) and it will still produce 50 mA of output.  Capice??

[benji]

yea arcman i understand,,what u do here is a current source,,my task is to do a variable voltage source (0>5 with current up to 1 amps)
i dont find a configuration to do that ,
i thought about hooking 2 0.6v diode in series at the output so i can drop the output voltage of the lm317 1.2 v
but this is not much reliable as different  currents would cause different voltage drops across the diodes and the output voltage would change.

[ArcMan]

OK.  I see. I was just going off of your OP, which said:

im building a robot that can charge stuff like batteries

In which case, the simplest way to do that is with a constant current source.

[benji]

im sorry for not making it quite clear
by the way ,,in the lm317 datasheet figure 6 is a voltage source from 0 >> 30
though im still trying to understand why the -10 v is there,,, i guess -1.25 would do ..

[RobD]

Hi Benji

Look at the MIC69502.  Adjustable down to 0.5v @ 5A.



 

[benji]

by the way, would a 20 m amp current source charge any battery?? even if the voltage is lower than the voltage of the battery?