I am trying to figure out a way to read current using a PIC microcontroller.
I came up with this little voltage divider.
I quickly realized that there will be only about 25 micro volts dropped across that .1 ohm resistor with a source voltage of 30 volts. Divide that by 6 (my divider) and lower my input voltage to a couple of volts and the difference between the two voltages is tiny. Probably beyond what the ADC on my PIC is going to be able to detect.
Is there a better way to do this? I figured I need an op amp but I found this project which uses no opamp.
Here is the voltage divider part. It makes no sense to me. It looks to me like both sides of that sense resistor are tied to ground???
What are they trying to do here?
So if I do really need an op amp. What do I need? I was thinking an Instrumentation Amp.
If I am on the right track:
1. Which op amp? I am thinking a rail to rail capable of a single +5 supply.
2. How do I determine the values of all of those resistors other than the gain resistor?
3. For the gain formula, what is AV? Is that the Amplified Voltage?
4. Where would I connect the inputs to my amp? Right across the sense resistor?
I came up with this little voltage divider.
I quickly realized that there will be only about 25 micro volts dropped across that .1 ohm resistor with a source voltage of 30 volts. Divide that by 6 (my divider) and lower my input voltage to a couple of volts and the difference between the two voltages is tiny. Probably beyond what the ADC on my PIC is going to be able to detect.
Is there a better way to do this? I figured I need an op amp but I found this project which uses no opamp.
Here is the voltage divider part. It makes no sense to me. It looks to me like both sides of that sense resistor are tied to ground???
What are they trying to do here?
So if I do really need an op amp. What do I need? I was thinking an Instrumentation Amp.
If I am on the right track:
1. Which op amp? I am thinking a rail to rail capable of a single +5 supply.
2. How do I determine the values of all of those resistors other than the gain resistor?
3. For the gain formula, what is AV? Is that the Amplified Voltage?
4. Where would I connect the inputs to my amp? Right across the sense resistor?
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