this is the only place i know that i can ask this ! sorry if its unrelated!!
im a little confused
1.if i put a resistor does it ONLY decrease the amperage? what to do to only limit my motors ampere usage without changing voltage? so i can run it from usb ! i don't care if the power is less (if it spins not good as full current)
2.how can i increase current (i don't care if voltage gets lower) i want to charge a phone with panel, when i connect it to switching regulator, it gets like from 100 amper to 90 or 80 amper (on bad lighting)
my panels are 9v and 12v , i want to make them 5v anyway, but current gets even lower!
if i want to increase voltage when its low and make it 5v when its higher, what should i do? so my phone doesn't keep going off and on ! (i can connect it to AA batteries and make the AA batteries charge my phone !or some lipo !)
edit: sorry, i see it now(mistakes in my post) i was so sleepy last night
1 ) You can use a resistor to lower the current to something small. A normal led can be set bright or dim with a resistors. A motor needs more current, and a resistor will get hot and will waste a lot of energy. You can not run a heavy motor from the usb power.
2 + 3 ) Are you talking about a solar panel ? Is that a very small solar panel of 100mA (milliAmpere) or is that a large solar panel on a roof of 100A ?
It is possible to make a lower voltage (with more current) with a DC-DC converter. You can also increase the voltage (with less current), and some DC-DC converters allow a stable output, while the input could be lower or higher.
It seems like you have to build a conceptual model of what electricity really is. Electricity is a form of energy. And it can only be converted into other forms of energy, like heat(resistors) light (leds) mechanical energy (motors) and electrical energy of another voltage(transformers and switching regulators).
A resistor converts electrical energy to heat. Just like friction converts mechanical energy to heat. Connecting a resistor in series incraeses the total resistance, thus lowering the current and introducing a voltage drop. The electrical power (=rate of energy conversion) converted to heat in the resistor is the current * voltage drop (P=U*I)
A switching regulator conserves energy while changing the voltage. But the process is not lossless. Your post was a bit hard to comprehend. The currents on the input side of the regulator (=output of solar panel) will be lower than on the output side of the regulator (=output to phone). So your post makes sense if we assume that you are comparing the output of the panel between direct connection and inserting a switching regulator. But the charging current should be larger with the regulator
Peter_n:
1 ) You can use a resistor to lower the current to something small. A normal led can be set bright or dim with a resistors. A motor needs more current, and a resistor will get hot and will waste a lot of energy. You can not run a heavy motor from the usb power.
2 + 3 ) Are you talking about a solar panel ? Is that a very small solar panel of 100mA (milliAmpere) or is that a large solar panel on a roof of 100A ?
It is possible to make a lower voltage (with more current) with a DC-DC converter. You can also increase the voltage (with less current), and some DC-DC converters allow a stable output, while the input could be lower or higher.
my solar panels are 12v both but gives 150a @ 10v at a good day here (its winter now, today is completely cloudy, i can't test again xD)
i don't think i can find that here, but i will try to find similiar one or make one myself if its simple !
i have a dc dc converter adjustable step down, but it makes current like 10% lower than full voltage ! i think its supposed to bring it higher !? what am i doing wrong?
nilton61:
It seems like you have to build a conceptual model of what electricity really is. Electricity is a form of energy. And it can only be converted into other forms of energy, like heat(resistors) light (leds) mechanical energy (motors) and electrical energy of another voltage(transformers and switching regulators).
A resistor converts electrical energy to heat. Just like friction converts mechanical energy to heat. Connecting a resistor in series incraeses the total resistance, thus lowering the current and introducing a voltage drop. The electrical power (=rate of energy conversion) converted to heat in the resistor is the current * voltage drop (P=U*I)
A switching regulator conserves energy while changing the voltage. But the process is not lossless. Your post was a bit hard to comprehend. The currents on the input side of the regulator (=output of solar panel) will be lower than on the output side of the regulator (=output to phone). So your post makes sense if we assume that you are comparing the output of the panel between direct connection and inserting a switching regulator. But the charging current should be larger with the regulator
You will have to use a stepup or boost regulator
then why is my Regulator's output current lower than solar panel's output current?(attaching the multiplier directly to panel (like short circuit)
You are testing with a current of 150A ? That is dangerous, the wires could melt.
A DC-DC converter that can handle a current of 150A should be a professional and certified device, installed by a qualified person.
When you want to test the shortcut current of a converter output, you better use a simple and small solar panel (about the size of a letter) that you use to test with.
1- I=E/R where a resistor increases R and decreases I as a result . So V won't change . Decrease V with Diodes , voltage drop . Beware that does affect I anyway .
2- I suppose OP-AMP or something like that .
Regulate them to 5v with a 'regulator'
3- A micro-controller + voltage detection module thingymajig , and drivers . In this case , a FET maybe even a BJT transistor might/would work but for higher voltages , it's cheaper and much more reliable to use relays .
You should just program the arduino to read the voltage and make a decision based on the value (stored in a variable )
Or if your phone needs 5v , you can regulate it . You might be able to use capacitors to store energy when there is extra and emit current when it's low .
Of course a battery is a much better choice . A Power bank is the best .
Besides , I'm not sure if amperage is a correct word . Widely used but I think Amp(s) is better .
But still, you can not measure the shortcut current to know something about the current output of a DC-DC converter. A good DC-DC converter might be protected against shortcut and might lower the current.
You could use two DC-DC converters, one to lower the voltage from the solar panel and one to increase the voltage from batteries. Or such a "anything" to 5V from Adafruit.
I assume that when the 9V and 12V solar panels are below 5V, they have so little current that you can not use it anyway.
The most common way is this: Use a large battery. For example a single Li-ion cell of 3.7V. Use a solar-to-battery-charger, so the battery is charged by the solar panels. This must be a special charger, so no current will flow back into the solar panel. The battery is then used to make other voltages. So when you need 5V, a normal DC-DC converter is used to turn the 3.7V into a useful 5V.
That means that for an output of 5V, the 12V of the solar panel is first converted into battery voltage and after that into 5V. It is a safe and common way to do it like that.
But still, you can not measure the shortcut current to know something about the current output of a DC-DC converter. A good DC-DC converter might be protected against shortcut and might lower the current.
You could use two DC-DC converters, one to lower the voltage from the solar panel and one to increase the voltage from batteries. Or such a "anything" to 5V from Adafruit.
I assume that when the 9V and 12V solar panels are below 5V, they have so little current that you can not use it anyway.
The most common way is this: Use a large battery. For example a single Li-ion cell of 3.7V. Use a solar-to-battery-charger, so the battery is charged by the solar panels. This must be a special charger, so no current will flow back into the solar panel. The battery is then used to make other voltages. So when you need 5V, a normal DC-DC converter is used to turn the 3.7V into a useful 5V.
That means that for an output of 5V, the 12V of the solar panel is first converted into battery voltage and after that into 5V. It is a safe and common way to do it like that.
That's a great idea thanks im going to do that. But a simple question, How can i charge and use the Lipo to charge my nexus 4 at same time ? (so i don't damage the lipo :|)
It should be no problem, to do that at the same time.
At www.adafruit.com they have a circuit board that does that. You add a Lipo or Li-ion cell and a solar panel. They show it at the end of a Youtube movie from Collin about solar energy.
Can you google for : collin lab solar adafruit
The symbol for the ampere is A not a. Thus you have mA, A, never ma or a.
All physical quantity single-letter symbols have a particular case and it usually matters.
For instance v is velocity, V is volts.
The full word symbol is almost always lower case, ampere, volt, farad, henry, ohm,
though getting this wrong isn't so confusing.
i found that the case, upper or lower, depend on whether the quantity was named after a person or not. Thus volt has a Capital V, ampere has a capital A, meter has a lowercase m and seconds have a lowercase s.
i was so sleepy last night 
or make one myself if its simple !