Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: benji on August 28, 2008, 09:42:15 AM
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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 ..
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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 (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.
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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
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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......
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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??
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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.
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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.
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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 ..
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Hi Benji
Look at the MIC69502. Adjustable down to 0.5v @ 5A.
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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?