I need a current sensor for MPPT based charge controller of max 10A current flowing.
Since the controller shouldn't be expensive, I don't want dedicated current sensors. So I have 2 alternatives:
1) Measuring voltage across Rsense using Op-amp.
2) Measuring voltage across Rsense by ADC of microcontroller.
I was wondered why no one is talking about using micro-controller for current sensing.
Upto now I plan to go for option 2. But please if there are certain things I must consider or if you have a better option, please suggest.

Bishal Paudel

 

The input voltage range of the ADC is almost certainly more than you want to drop across a current sense resistor.

 

The input voltage range of the ADC is almost certainly more than you want to drop across a current sense resistor.

I think I will use 0.001 ohm resistor or lower. SO the drop will be less than 0.1V.

 

You will have to use an opamp to amplify the voltage across Rsense anyway. But using a ground based Rsense in this case will work just fine. And it will be much simpler than using a differential approach. Like option 1.
For precession current measurement. A 10 bit ADC will not be quite optional. And I guess that is why you can not find much about it. But again in your application. If you can utilize the full of the ADC measurement span. I guess it will work fine

 

I think I will use 0.001 ohm resistor or lower. SO the drop will be less than 0.1V.

And the input voltage range of a microcontroller's ADC is typically going to be 10 to 50 times that, meaning that you will be losing 3 to 6 bits of resolution right off the bat. Unless you go back to option #1 and use an opamp to amplify the signal to something that better matches the MCU's input range.

 

Here's my basic circuit I think I will start with:http://tinypic.com/r/2va1aoz/6

 

Not the worst idea... though the national code does not allow resistors in the return leg so this is a hobby use only design.

Your amp has a gain of about 134. The sense resistor will have it's max drop of 10A * .01 ohms or 0.01 volts. So it's output is 13.4 volts... a little large don't you think?

I didn't check the specs of the LM2904 but it must include a voltage range down to ground, as that is the low end of your signal.

When I do this I use a high side current sense chip. Maxim and several other places make them.

 

i modified my design as that of 3A, sorry for that as I am now doing only for 40 watt panel. so I think the voltage out max will be 4V.

 

I think its a lot nicer to just use a high side current sensing chip.

 

Not the worst idea... though the national code does not allow resistors in the return leg so this is a hobby use only design.

Your amp has a gain of about 134. The sense resistor will have it's max drop of 10A * .01 ohms or 0.01 volts. So it's output is 13.4 volts... a little large don't you think?

I didn't check the specs of the LM2904 but it must include a voltage range down to ground, as that is the low end of your signal.

When I do this I use a high side current sense chip. Maxim and several other places make them.

I want a circuit which will sense the current input from PV or a 12 volt battery plus the output current drawn by load. A microcontroller has to sense the current and switch accordingly..... Is there any efficient method.... As to ADC usually a voltage is input and to be compared and digitized.... any idea or sensing circuit in proteus plz???????????

 

I want a circuit which will sense the current input from PV or a 12 volt battery plus the output current drawn by load. A microcontroller has to sense the current and switch accordingly..... Is there any efficient method.... As to ADC usually a voltage is input and to be compared and digitized.... any idea or sensing circuit in proteus plz???????????

For complete isolation use a Hall effect sensor. Most will directly interface with the ADC. http://ampsolution.com/AMPSOLUTION.html

 

how to detect blockage in seeder nozzle using sensor. option of using light and photodiode is not allowed
plz inform me if any other option is there

 

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